Dry-Pipe Fire Sprinkler Systems

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−---

−title: Dry-Pipe Fire Sprinkler Systems

−category: Fire Protection

−toc_depth: 3

−description: >

− When to use: Automatic dry-pipe fire sprinkler systems for buildings or portions of buildings where sprinkler piping is exposed to ambient temperatures at or below 40°F (4°C) and cannot be reliably maintained above freezing. Typical applications include unheated parking garages, loading docks, attics and concealed combustible spaces, canopies and exterior walkways, freezer warehouses, refrigerated storage rooms, mechanical penthouses, and unconditioned shell space in tenant-fit-up projects. Covers the complete above-ground system from the dry-pipe valve through supply mains, cross mains, branch lines, dry sprinklers, the air supply (compressor or nitrogen generator), quick-opening devices, drains and drum drips, alarm and supervisory devices, and the fire department connection. Addresses light hazard, ordinary hazard (Groups 1 and 2), and extra hazard (Groups 1 and 2) occupancies that require dry-pipe protection.

− Not intended for: Wet-pipe systems in conditioned occupied spaces (see [[sync/wet-pipe-fire-sprinkler-systems]]); pre-action systems for high-value, data center, freezer-storage, or other applications requiring a second event before water is admitted to the piping; deluge systems for aircraft hangars, transformer suppression, and similar open-head applications; antifreeze loops (which are wet-pipe variants for limited freeze protection of small areas); residential systems designed to NFPA 13R or NFPA 13D; underground fire service mains (see [[sync/domestic-water-piping]] for related water-service work and [[sync/fire-pumps]] for pumped supplies); standpipe and hose systems (see [[sync/standpipe-systems]]); or fire alarm initiating and notification circuits beyond the dry-pipe valve waterflow and supervisory connections (see [[sync/fire-alarm-systems]]).

−---

−

−# Scope {toc}

−

−## This standard covers the design documentation requirements, materials, installation, testing, and acceptance criteria for automatic dry-pipe fire sprinkler systems. {note}

−## In a dry-pipe system the piping downstream of the dry-pipe valve is held under pressurized air or nitrogen rather than water. {note}

−## When one or more sprinklers open in response to heat, the supervisory gas escapes, the differential clapper in the dry-pipe valve trips, and water is admitted to the system and discharged through the open sprinklers. {note}

−

−## The scope extends from the supply-side connection at the dry-pipe valve assembly — including the trim, priming water connection (where used), air or nitrogen supply, accelerator or quick-opening device, intermediate chamber drain, and main drain — through all above-ground supply mains, cross mains, branch lines, and branch line end connections to the individual sprinklers. {note}

−## Auxiliary drains (drum drips) at low points, valve supervisory devices, the waterflow alarm pressure switch, the fire department connection, system pitch and drainage requirements, hanger and seismic bracing arrangements specific to dry-system pipe loading, and the system pressure-control air supply are included. {note}

−

−## Dry-pipe systems shall be the predominant choice wherever sprinkler piping cannot be maintained above 40°F (4°C), including unheated parking structures, exterior canopies, freezer warehouses, refrigerated rooms, mechanical penthouses, and other unconditioned spaces where a wet-pipe system would be vulnerable to freezing damage.

−

−## Water delivery time, not just hydraulic flow, is a defining constraint on a dry-pipe system, and the hydraulic design and the system volume govern all components together. {note}

−

−## Dry-pipe systems installed under this standard shall comply with NFPA 13, Standard for the Installation of Sprinkler Systems (current edition adopted by the Authority Having Jurisdiction), the International Fire Code (IFC), and the International Building Code (IBC) as adopted locally.

−

−## Where local amendments modify NFPA 13 requirements, the local amendment shall govern unless it is less stringent than the base standard, in which case the base standard governs.

−

−## The Contractor and the designer shall confirm the edition of NFPA 13 adopted in the jurisdiction prior to beginning design work.

−

−## Each successive edition of NFPA 13 has introduced meaningful changes to system volume limits, water delivery time, listed nitrogen-inerting allowances, pipe joining, and corrosion protection that affect both design and material procurement. {note}

−

−## This standard does not govern occupancy-specific or commodity-specific dry-pipe sprinkler systems designed under the storage chapters of NFPA 13 (rack storage in cold storage, frozen food warehouses, high-piled storage in unheated structures), which require specialized density, area, in-rack sprinkler, and water-delivery analysis beyond the scope of this document.

−

−## The Engineer of Record shall confirm whether storage-specific rules apply to any portion of the building before releasing this standard for use on a project.

−

−## Pre-action and deluge systems, although mechanically related to dry-pipe systems, are covered by separate SynC standards. {note}

−

−# Differentiation from Wet-Pipe Systems {toc}

−

−## Wet-pipe systems are mechanically simpler, deliver water immediately upon sprinkler opening, and have fewer maintenance points than dry-pipe systems. {note}

−## NFPA 13 Section 8.2 requires that wet-pipe systems be used wherever piping can be reliably maintained above 40°F (4°C). {note}

−

−## A dry-pipe system shall not be substituted for a wet-pipe system where a wet-pipe system is feasible.

−

−## Dry-pipe systems shall be selected only when freeze protection is required and when neither electric heat trace with insulation, antifreeze loops within the size limits permitted by NFPA 13, nor relocation of piping into conditioned space is practical.

−

−## The Engineer of Record shall document the rationale for selecting a dry-pipe system in lieu of a wet-pipe system in the basis-of-design narrative.

−

−```datasheet

−label: Reason for Dry-Pipe Selection

−type: select

−drawing_ref: true

−options:

− - "Unheated attic, concealed, or joist space"

− - "Parking garage or other unconditioned occupied space"

− - "Exterior canopy or walkway"

− - "Loading dock with overhead doors"

− - "Mechanical penthouse vented to exterior"

− - "Refrigerated cold storage room (35°F to 50°F)"

− - "Freezer warehouse (below 32°F)"

− - "Other — see basis of design"

−default: "Unheated attic, concealed, or joist space"

−```

−

−## Common decision drivers that justify a dry-pipe selection are piping in attics, joist spaces, or concealed ceiling spaces in cold climates where intermittent heating is uncertain; freezer warehouse and refrigerated storage room protection; unheated parking decks above grade; exterior canopies and walkways; unconditioned loading dock areas with overhead doors that defeat space heating; and mechanical rooms vented to outside air. {note}

−

−## The decision to use a dry-pipe system shall not be made on construction cost alone.

−

−## The Owner shall be informed of the operational cost difference before the design is finalized, because a dry-pipe system has a meaningfully higher long-term inspection, testing, and maintenance burden than a wet-pipe system.

−

−# Referenced Standards {toc}

−

−## Materials, design, installation, and testing shall comply with the current adopted editions of the following standards.

−

−| Standard | Title |

−|----------|-------|

−| NFPA 13 | Standard for the Installation of Sprinkler Systems |

−| NFPA 20 | Standard for the Installation of Stationary Pumps for Fire Protection |

−| NFPA 24 | Standard for the Installation of Private Fire Service Mains and Their Appurtenances |

−| NFPA 25 | Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems |

−| NFPA 70 | National Electrical Code |

−| NFPA 72 | National Fire Alarm and Signaling Code |

−| NFPA 291 | Recommended Practice for Fire Flow Testing and Marking of Hydrants |

−| IBC | International Building Code |

−| IFC | International Fire Code |

−| ASTM A53 | Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-Coated, Welded and Seamless |

−| ASTM A135 | Standard Specification for Electric-Resistance-Welded Steel Pipe |

−| ASTM A234 | Standard Specification for Piping Fittings of Wrought Carbon Steel and Alloy Steel for Moderate and High Temperature Service |

−| ASTM A795 | Standard Specification for Black and Hot-Dipped Zinc-Coated (Galvanized) Welded and Seamless Steel Pipe for Fire Protection Use |

−| ASME B16.5 | Pipe Flanges and Flanged Fittings |

−| ASME B16.9 | Factory-Made Wrought Buttwelding Fittings |

−| ASME B16.11 | Forged Fittings, Socket-Welding and Threaded |

−| UL 199 | Automatic Sprinklers for Fire Protection Service |

−| UL 260 | Dry Pipe Valves for Fire Protection Service |

−| UL 262 | Gate Valves for Fire Protection Service |

−| UL 312 | Check Valves for Fire Protection Service |

−| UL 753 | Alarm Accessories for Automatic Water-Supply Control Valves for Fire Protection Service |

−| UL 1091 | Butterfly Valves for Fire Protection Service |

−| FM Global 2008 | Approval Standard for Dry-Pipe Valves and Their Trim |

−| FM Global 2011 | Approval Standard for Accelerators for Dry-Pipe Valves |

−| FM Global 2024 | Approval Standard for Air Maintenance Devices for Sprinkler Systems |

−| FM Global DS 2-0 | Installation Guidelines for Automatic Sprinklers |

−| FM Global DS 2-1 | Corrosion in Automatic Sprinkler Systems |

−| ANSI/AWWA C606 | Grooved and Shouldered Joints |

−

−## Where standards conflict, the more stringent requirement shall govern unless directed otherwise by the Engineer of Record in writing.

−

−# Submittals {toc}

−

−## Action Submittals {toc}

−

−### The Contractor shall submit the following for the Engineer of Record's review and the Authority Having Jurisdiction's approval prior to procurement and installation.

−### The submittal package for a dry-pipe system is more demanding than for a wet-pipe system because the AHJ uses the package to verify both hydraulic compliance and the water delivery time requirement, which depends on the calculated system volume and the air supply arrangement. {note}

−

−### The following items shall be submitted as a coordinated package:

−

−- Working drawings for the sprinkler system complying with NFPA 13 Chapter 28, including floor plans showing pipe routing, pipe sizes, sprinkler types, locations, and elevations; riser diagrams; hydraulic reference node diagram; pitch and drainage details with all auxiliary drain (drum drip) locations and elevations clearly indicated; and details of the dry-pipe valve assembly, air supply, and quick-opening device

−- Hydraulic calculations performed by the pipe-sizing method, demonstrating that the system meets the design density and area requirements for each hazard area, with the water demand plotted against the water supply curve including all hose stream allowances and with the required safety margin demonstrated at the design point

−- A calculated system volume (gallons or cubic feet) for the entire dry-pipe system, and where the volume exceeds the threshold for water delivery analysis, a water delivery time calculation demonstrating that water reaches the inspector's test connection in 60 seconds or less from the time the inspector's test valve is opened

−- Product data for the dry-pipe valve, the accelerator or quick-opening device (where used), the air maintenance device or nitrogen generator, the air compressor (where used), all sprinklers including dry sprinkler barrel lengths and trim, valve supervisory switches, waterflow pressure switch, fire department connection, and hangers

−- Manufacturer's installation instructions for the dry-pipe valve, accelerator, and nitrogen generator, including any limitations on application, system arrangement, or air-leakage tolerance that affect compliance

−- A pipe pitch and drainage plan showing all low points, drum drip locations, main drain, and auxiliary drains, with elevation callouts that confirm compliance with the minimum pitch required by NFPA 13 (1/2 in. per 10 ft for branch lines and 1/4 in. per 10 ft for mains in steel-pipe systems)

−- Seismic bracing calculations, where seismic bracing is required by the project's Seismic Design Category

−

−```datasheet

−label: Action Submittals Required

−type: checkbox

−options:

− - "Working drawings per NFPA 13 Chapter 28"

− - "Hydraulic calculations"

− - "System volume calculation"

− - "Water delivery time calculation"

− - "Product data for all components"

− - "Manufacturer installation instructions"

− - "Pipe pitch and drainage plan with drum drip locations"

− - "Seismic bracing calculations (if required)"

−default: "Working drawings per NFPA 13 Chapter 28"

−```

−

−### No work shall proceed on any portion of the dry-pipe system until the corresponding submittals are reviewed, returned, and any required approval from the AHJ is in hand.

−

−### The Contractor shall submit the coordinated submittal package items listed above for the Engineer of Record's review and the AHJ's approval prior to procurement and installation.

−

−### Working drawings shall be prepared by or under the supervision of a person with qualifications acceptable to the AHJ.

−

−### The Contractor shall confirm designer qualification requirements before assigning the design work, because in many jurisdictions this means a licensed fire protection engineer or a NICET-certified designer at the level required by state law.

−

−## Closeout Submittals {toc}

−

−### The following shall be submitted at substantial completion before the dry-pipe system is accepted:

−

−- Contractor's Material and Test Certificate for Aboveground Piping (NFPA 13 Figure 29.1.1), signed by the installing contractor, certifying the pipe and fittings materials, joint types, flushing procedure, hydrostatic test results, air pressure test results, dry-pipe valve trip test results, water delivery time, alarm device operation, and inspector's test valve performance

−- As-built drawings reflecting field changes from the reviewed working drawings, including any modifications to drum drip locations or pipe pitch

−- Operation and maintenance manual including dry-pipe valve impairment procedures, air supply maintenance instructions, seasonal drain-down procedures for drum drips, NFPA 25 inspection intervals, and the manufacturer's reset procedure for the dry-pipe valve

−- Warranty documentation for all components carrying a manufacturer warranty

−- Hydraulic and water delivery design information signs confirming that installed signs match the design calculations

−- Air leakage test record demonstrating compliance with the NFPA 13 air-leakage limit of 1.5 psi per 24 hours

−

−```datasheet

−label: Closeout Submittals Required

−type: checkbox

−options:

− - "Contractor's Material and Test Certificate for Aboveground Piping"

− - "Dry-pipe valve trip test record"

− - "Water delivery time test record"

− - "Air leakage test record (1.5 psi per 24 hours)"

− - "As-built drawings"

− - "Operation and maintenance manual"

− - "Manufacturer warranty documentation"

− - "Hydraulic and water delivery design information signs"

−default: "Contractor's Material and Test Certificate for Aboveground Piping"

−```

−

−### The Contractor shall submit the closeout submittal items listed above at substantial completion before the dry-pipe system is accepted.

−

−# Quality Assurance {toc}

−

−## Installer Qualifications {toc}

−

−### Dry-pipe systems require specific design expertise beyond ordinary wet-pipe work. {note}

−

−### Dry-pipe sprinkler system installation shall be performed by a licensed fire protection contractor as required by the state and local jurisdiction.

−

−### In states where licensing is mandatory, the installing contractor shall hold a current fire protection contractor's license.

−

−### The individual preparing the working drawings and hydraulic calculations shall hold qualifications as required by the AHJ.

−

−### Where state law requires NICET certification, the designer shall hold NICET Level III or Level IV certification in water-based systems layout or fire protection engineering technology, as applicable.

−

−### The designer shall demonstrate prior experience with system volume sizing, water delivery time analysis, air supply selection, and quick-opening device integration.

−

−### Where the Contractor's in-house designer has limited dry-pipe experience, the design shall be subcontracted to a qualified fire protection engineering consultant or peer-reviewed by one.

−

−### The Contractor shall identify the design lead on the working drawings.

−

−## Coordination with Other Trades {toc}

−

−### The sprinkler Contractor shall coordinate early and continuously with the mechanical, electrical, structural, and architectural trades.

−### Dry-pipe systems impose additional coordination requirements beyond a wet-pipe system. {note}

−

−### The dry-pipe valve room or enclosure shall be in a heated space adjacent to the protected area.

−

−### The air compressor or nitrogen generator requires dedicated electrical service and possibly ventilation.

−

−### Auxiliary drains shall be accessible at every low point in the pipe network, including drains hidden above ceilings or in concealed combustible spaces.

−

−### The slope of the building structure may dictate pipe pitch direction and the resulting drum drip count. {note}

−

−### The location and structural capacity of the building structure to which hangers and seismic braces attach shall be confirmed with the structural engineer before hanger installation begins.

−

−### Hanger design loads shall account for the water-filled pipe weight plus an allowance for residual water that may remain after a trip, because dry-pipe pipe is filled with water during a hydrostatic test and during any post-trip discharge.

−

−## Listing and Approval {toc}

−

−### All sprinklers, dry-pipe valves, accelerators or quick-opening devices, air maintenance devices, nitrogen generators serving dry-pipe systems, valves, hangers, seismic brace assemblies, and alarm devices shall be listed by a Nationally Recognized Testing Laboratory (UL, FM, or another NRTL as accepted by the AHJ) for the specific application and service conditions.

−

−### Dry sprinklers shall be listed to UL 199 and shall be applied in accordance with their listing barrel length, orientation, and pendent or upright configuration.

−

−### The dry-pipe valve shall be listed to UL 260 and, where required by the Owner's insurance carrier, also approved to FM 2008.

−

−### Accelerators shall be listed and, where FM compliance is required, approved to FM 2011.

−

−### Air maintenance devices shall be listed and, where FM compliance is required, approved to FM 2024.

−

−## FM Global Compliance {toc}

−

−### Where the building's property insurance carrier or the Owner requires FM Global compliance, all components shall be FM-approved in addition to UL-listed.

−

−```datasheet

−label: FM Global Compliance Required

−type: radio

−options:

− - "Not required"

− - "Required — FM-approved components throughout"

−default: "Not required"

−```

−

−### A component that is UL-listed may not be FM-approved, and the difference is consequential for insurance purposes. {note}

−

−### The Contractor shall confirm FM approval status for each product at procurement, not after installation.

−

−## Corrosion Protection {toc}

−

−### Internal corrosion is a more aggressive problem in dry-pipe systems than in wet-pipe systems. {note}

−### The repeated wet-dry cycling of residual water trapped at low points, combined with the high oxygen content of air used as the supervisory gas, creates an environment in which microbiologically influenced corrosion (MIC) and oxygen-driven pitting can perforate the pipe wall in 10 to 20 years on systems that are not properly designed and maintained. {note}

−

−### NFPA 13 (2022 edition and later) recognizes nitrogen inerting as an alternative to galvanized pipe for corrosion control on dry-pipe systems. {note}

−

−### The Contractor shall provide one of three corrosion-mitigation approaches: galvanized steel pipe throughout the dry-pipe portion; nitrogen inerting of the dry-pipe system using a listed nitrogen generator that displaces oxygen; or both galvanized pipe and nitrogen inerting where the Owner's risk profile, insurance requirements, or service history warrants enhanced protection.

−

−```datasheet

−label: Corrosion Mitigation Approach

−type: radio

−options:

− - "Galvanized steel pipe throughout, air supervised"

− - "Black steel pipe, nitrogen inerted"

− - "Galvanized steel pipe, nitrogen inerted (enhanced protection)"

− - "Black steel pipe, air supervised (existing system replication only)"

−default: "Galvanized steel pipe throughout, air supervised"

−```

−

−### Where nitrogen is used, the system shall be evacuated of air and refilled with nitrogen to the listed purity level — typically 98 percent nitrogen or greater at the sprinkler.

−

−### Where nitrogen is used, the nitrogen generator shall be supplied with adequate compressed air capacity to maintain pressure during system leakage.

−

−# Environmental and Service Conditions {toc}

−

−## Temperature Range {toc}

−

−### Dry-pipe systems are designed to operate where the protected space drops below 40°F (4°C). {note}

−

−### The dry-pipe valve itself shall be installed in a heated enclosure or valve room maintained at not less than 40°F at all times.

−

−```datasheet

−label: Dry-Pipe Valve Room Minimum Temperature

−type: range

−unit: °F

−options:

− min: 40

− max: 70

− setpoints: [40, 50, 60, 70]

−default: 50

−```

−

−### The valve trim, priming water (where used), and supply-side piping shall not be allowed to freeze.

−

−### Where the protected space is a freezer, refrigerated room, or other deeply chilled environment, the designer shall account for the temperature differential at the valve-room-to-cold-space boundary and shall provide insulation, heat trace, or vapor barriers as required to prevent moisture migration into the dry-pipe piping during defrost cycles.

−

−```datasheet

−label: Minimum Protected Space Temperature

−type: range

−unit: °F

−drawing_ref: true

−options:

− min: -40

− max: 40

− setpoints: [-40, -20, 0, 20, 32, 35, 40]

−default: 0

−```

−

−## Maximum Working Pressure {toc}

−

−### The supply pressure to the dry-pipe valve also determines the required air pressure: a differential dry-pipe valve requires the air pressure to be maintained above a manufacturer-specified ratio of the water supply pressure (commonly 20 psi plus 25 percent of the maximum water supply pressure) to keep the clapper seated against false trips. {note}

−

−### The system air or nitrogen pressure shall be specified based on the water supply pressure and the dry-pipe valve manufacturer's required pressure ratio.

−

−```datasheet

−label: System Air or Nitrogen Pressure

−type: range

−unit: psi

−options:

− min: 15

− max: 60

− setpoints: [15, 20, 25, 30, 40, 50, 60]

−default: 40

−```

−

−### The system working pressure shall not exceed 175 psi at the dry-pipe valve unless the system is designed and the components are rated for a higher pressure.

−

−```datasheet

−label: System Working Pressure

−type: range

−unit: psi

−drawing_ref: true

−options:

− min: 40

− max: 250

− setpoints: [40, 100, 125, 150, 175, 200, 250]

−default: 150

−```

−

−### Where the water supply static pressure exceeds 175 psi, a pressure-reducing valve shall be provided on the supply to the dry-pipe valve.

−

−# Design Basis and Hazard Classification {toc}

−

−## Occupancy Hazard Classification {toc}

−

−### Hazard classification is the single most consequential design decision for a sprinkler system because it directly determines the design density, the design area, and therefore the flow and pressure demand on the water supply. {note}

−### An incorrect hazard classification produces a system that is either inadequately protected (a life-safety deficiency) or grossly over-designed (an unnecessary capital cost). {note}

−

−### Light Hazard occupancies are characterized by low rates of heat release; in dry-pipe applications they include unheated office or institutional spaces, attic protection over light hazard occupancies, and exterior canopies over public assembly entrances. {note}

−### Ordinary Hazard Group 1 occupancies have moderate rates of heat release, with representative dry-pipe applications including unheated parking garages, mechanical penthouses, and loading docks. {note}

−### Ordinary Hazard Group 2 occupancies have higher rates of heat release, with representative dry-pipe applications including freezer warehouses (subject to NFPA 13 storage chapter cross-references), unheated repair garages, and certain industrial mezzanines. {note}

−

−### The hazard classification shall be assigned by the designer based on the occupancy descriptions in NFPA 13 Chapter 5 and shall be confirmed with the Owner and the AHJ prior to finalizing the hydraulic design.

−

−```datasheet

−label: Predominant Occupancy Hazard Classification

−type: select

−drawing_ref: true

−options:

− - "Light Hazard"

− - "Ordinary Hazard Group 1"

− - "Ordinary Hazard Group 2"

− - "Extra Hazard Group 1"

− - "Extra Hazard Group 2"

−default: "Ordinary Hazard Group 1"

−```

−

−### Extra Hazard occupancies are uncommon in dry-pipe applications because the high design density combined with the dry-pipe water delivery delay magnifies the risk. {note}

−

−### Where an Extra Hazard space requires freeze protection, a pre-action system or relocation into conditioned space shall be considered as alternatives before defaulting to a dry-pipe system.

−

−### NFPA 13 imposes additional restrictions on Extra Hazard dry-pipe systems, including reduced system volume limits. {note}

−

−## Design Density and Area {toc}

−

−### Design density and design area shall be determined from NFPA 13 Table 19.2.3.1.1 for the applicable hazard classification, with the dry-pipe adjustment applied.

−

−```datasheet

−label: Design Density

−type: range

−unit: gpm/sq ft

−drawing_ref: true

−options:

− min: 0.10

− max: 0.60

− setpoints: [0.10, 0.15, 0.20, 0.30, 0.40, 0.45, 0.60]

−default: 0.15

−```

−### For example, an Ordinary Hazard Group 1 dry-pipe system designed at 0.15 gpm/sq ft uses a design area of 1,950 sq ft rather than the 1,500 sq ft used for the equivalent wet-pipe system. {note}

−

−### NFPA 13 requires the design area for a dry-pipe system to be increased by 30 percent over the wet-pipe design area for the same hazard classification, in recognition of the delayed water delivery and the resulting larger fire size that may develop before water reaches the open sprinklers.

−

−```datasheet

−label: Design Area (dry-pipe, 30% increase applied)

−type: range

−unit: sq ft

−drawing_ref: true

−options:

− min: 1950

− max: 6500

− setpoints: [1950, 2600, 3250, 3900, 5200, 6500]

−default: 1950

−```

−

−### The 30 percent dry-pipe area increase is mandatory and shall not be reduced by the designer based on engineering judgment alone.

−

−### Where the system is equipped with a listed quick-opening device that meets the water delivery time requirement, the 30 percent area increase still applies; the quick-opening device shortens delivery time but does not eliminate the underlying delay.

−

−## Hose Stream Allowance {toc}

−

−### The hose stream allowance for a dry-pipe system is the same as for a wet-pipe system at the same hazard classification: 100 gpm for light hazard, 250 gpm for ordinary hazard, and 500 gpm for extra hazard. {note}

−

−### The hose stream allowance shall be specified to match the hazard classification of the sprinkler design.

−

−```datasheet

−label: Hose Stream Allowance

−type: select

−unit: gpm

−options:

− - "100 gpm (Light Hazard)"

− - "250 gpm (Ordinary Hazard)"

− - "500 gpm (Extra Hazard)"

−default: "250 gpm (Ordinary Hazard)"

−```

−

−### The hose stream demand shall be applied simultaneously with the sprinkler demand at the design area.

−

−## Water Supply Verification {toc}

−

−```datasheet

−label: Water Supply Source

−type: select

−options:

− - "Public water main — flow test required"

− - "Dedicated fire water storage tank and pump"

− - "Combined public main and storage tank"

−default: "Public water main — flow test required"

−```

−

−```datasheet

−label: Static Pressure at Flow Test

−type: range

−unit: psi

−drawing_ref: true

−options:

− min: 20

− max: 150

− setpoints: [20, 40, 50, 60, 70, 80, 90, 100, 120, 150]

−default: 70

−```

−

−```datasheet

−label: Residual Pressure at Flow Test

−type: range

−unit: psi

−drawing_ref: true

−options:

− min: 10

− max: 130

− setpoints: [10, 20, 30, 40, 50, 60, 70, 80, 100, 130]

−default: 50

−```

−

−### Water supply data shall be obtained by a hydrant flow test conducted at or near the project site in accordance with NFPA 291.

−

−### The flow test shall have been conducted no more than 12 months prior to the date of submittal.

−

−### Static pressure, residual pressure, and pitot flow shall be recorded.

−

−### The designer shall plot the water supply curve and confirm that the system demand including hose stream falls below the supply curve with the safety margin required by NFPA 13.

−

−### Where the available water supply does not meet the system demand, a fire pump shall be provided per [[sync/fire-pumps]].

−

−# System Volume and Water Delivery Time {toc}

−

−## System Volume {toc}

−

−### System volume — the total internal volume of the dry-pipe piping downstream of the dry-pipe valve — is the dominant constraint on dry-pipe system design. {note}

−### A larger volume means more air to expel before water flows, which means slower water delivery. {note}

−### Systems above 750 gallons commonly require a listed accelerator or other quick-opening device, nitrogen inerting (which allows the listed gas-displacement curve to be used), and/or subdivision into multiple dry-pipe systems served by separate dry-pipe valves. {note}

−

−### New dry-pipe systems shall not exceed 750 gallons (2,840 L) unless the designer demonstrates by calculation that water reaches the most remote inspector's test connection within 60 seconds of the test valve being opened.

−

−```datasheet

−label: Calculated System Volume

−type: range

−unit: gal

−drawing_ref: true

−options:

− min: 50

− max: 1500

− setpoints: [50, 100, 250, 500, 750, 1000, 1250, 1500]

−default: 500

−```

−

−### The designer shall calculate system volume early in the design process — before pipe routing is finalized — so that any volume mitigations (subdivision, accelerator, nitrogen) can be incorporated into the layout.

−

−```datasheet

−label: System Volume Mitigation Strategy

−type: select

−options:

− - "Volume below 750 gal — no mitigation required"

− - "Quick-opening device (accelerator) provided"

− - "Nitrogen inerting per NFPA 13"

− - "System subdivided into multiple dry-pipe valves"

− - "Combination — accelerator and subdivision"

− - "Combination — accelerator and nitrogen inerting"

−default: "Volume below 750 gal — no mitigation required"

−```

−

−### Adding volume mitigations after the fact is significantly more expensive than designing for them from the beginning. {note}

−

−## Water Delivery Time {toc}

−

−### This is the defining performance criterion for a dry-pipe system. {note}

−### The water delivery time depends on system volume, pipe diameter and arrangement, air pressure, water supply pressure, and the presence or absence of a quick-opening device. {note}

−

−### Water shall reach the inspector's test connection at the hydraulically most remote point of the system within 60 seconds of opening the inspector's test valve, measured from the time the test valve is fully open.

−

−```datasheet

−label: Water Delivery Time (calculated)

−type: range

−unit: seconds

−options:

− min: 15

− max: 60

− setpoints: [15, 20, 30, 40, 50, 60]

−default: 60

−```

−

−### For systems exceeding 750 gallons, the designer shall submit a water delivery time calculation using one of the accepted methods: the NFPA 13 spreadsheet-based volume/pressure method; a manufacturer's accelerator-specific delivery time calculation; or a computational fluid dynamics analysis where the geometry is too complex for tabular methods.

−

−### The AHJ may require a field water delivery test at acceptance to confirm the calculation.

−

−# Dry-Pipe Valve Assembly {toc}

−

−## Dry-Pipe Valve Type {toc}

−

−### The dry-pipe valve is the heart of the system. {note}

−### It is a listed differential-area valve in which the lower-pressure air on the clapper outlet acts on a larger area than the higher-pressure water on the clapper inlet, producing a force balance that keeps the clapper seated. {note}

−### When sprinkler operation releases the system air, the force balance collapses and the clapper opens to admit water. {note}

−

−### Differential dry-pipe valves are the historical standard and require an air-to-water pressure ratio of approximately 1:6 — that is, 25 psi of air will hold against 150 psi of water. {note}

−### Low-differential dry-pipe valves use a smaller differential area and require air pressure closer to the water pressure, but with the benefit of faster trip response. {note}

−### Low-differential valves are increasingly common because they pair well with nitrogen inerting (where nitrogen pressure is held closer to water pressure for a tighter operational margin). {note}

−

−### The dry-pipe valve type shall be specified as a differential or low-differential valve, considering compatibility with nitrogen inerting.

−

−```datasheet

−label: Dry-Pipe Valve Type

−type: radio

−options:

− - "Differential dry-pipe valve (standard ratio)"

− - "Low-differential dry-pipe valve"

−default: "Differential dry-pipe valve (standard ratio)"

−```

−

−### The dry-pipe valve size shall be specified to match the hydraulic design of the system.

−

−```datasheet

−label: Dry-Pipe Valve Size

−type: select

−unit: in

−drawing_ref: true

−options:

− - "2 in."

− - "2-1/2 in."

− - "3 in."

− - "4 in."

− - "6 in."

− - "8 in."

−default: "4 in."

−```

−

−### The dry-pipe valve body and trim material shall be specified based on the service environment of the valve location.

−

−```datasheet

−label: Dry-Pipe Valve Body Material

−type: radio

−options:

− - "Cast iron body, bronze trim"

− - "Ductile iron body, stainless steel trim"

−default: "Cast iron body, bronze trim"

−```

−

−## Valve Trim {toc}

−

−### The dry-pipe valve assembly shall be furnished with the manufacturer's standard listed trim, including a water-side pressure gauge and an air-side (or nitrogen-side) pressure gauge allowing the operator to confirm both pressures and clapper seating; an intermediate chamber drain that drains the small volume of priming water above the clapper to allow the valve to be reset after a trip; a main drain valve; an automatic ball drip on the supply piping between the dry-pipe valve and the fire department connection; a water-supply alarm pressure switch or waterflow alarm device that signals the fire alarm system when water enters the dry-pipe piping; and an air or nitrogen supply connection with a check valve, isolation valve, and pressure regulator as required by the air supply type.

−

−### The dry-pipe valve assembly shall be furnished with the manufacturer's standard listed trim.

−

−### The trim is not optional and shall not be field-assembled from non-listed parts.

−

−### The intermediate chamber shall be visibly observable through a sight glass or test cock so that the technician can confirm the chamber is dry before resetting.

−

−### The main drain valve shall be sized not smaller than 2 in. for draining the system after a trip or for periodic main drain testing.

−

−### The automatic ball drip shall drain any water that enters the FDC piping during cold weather without back-pressuring the dry-pipe valve.

−

−## System Control Valve {toc}

−

−```datasheet

−label: System Control Valve Type

−type: radio

−options:

− - "OS&Y gate valve (interior riser)"

− - "Post-indicator valve (exterior / yard service)"

− - "Indicating butterfly valve with supervisory switch"

−default: "OS&Y gate valve (interior riser)"

−```

−

−### The system supply to the dry-pipe valve shall be controlled by a listed indicating control valve installed upstream of the dry-pipe valve, in the same manner as a wet-pipe system.

−

−### The control valve shall be of the indicating type — OS&Y gate valve listed to UL 262, indicating butterfly valve listed to UL 1091, or post-indicator valve at exterior locations.

−

−## Valve Supervision {toc}

−

−```datasheet

−label: Dry-Pipe Valve Supervisory Signals

−type: checkbox

−options:

− - "Low air or nitrogen pressure supervisory switch"

− - "High air or nitrogen pressure supervisory switch"

− - "Valve room low-temperature supervisory switch (40°F)"

− - "Main control valve tamper switch"

−default: "Low air or nitrogen pressure supervisory switch"

−```

−

−### The system control valve and any other valves controlling water to the dry-pipe system shall be supervised open by an electrically supervised tamper switch connected to the fire alarm system or an approved supervising station, in accordance with NFPA 72 and NFPA 13.

−

−### The dry-pipe valve assembly itself shall be equipped with a low-air-pressure supervisory switch that signals the fire alarm system when the air pressure falls below the listed minimum, indicating a system leak.

−

−# Quick-Opening Devices {toc}

−

−## Accelerators {toc}

−

−### The most common quick-opening device (QOD) is an accelerator, a listed device installed at the dry-pipe valve that detects the rate of air pressure drop in the system and rapidly equalizes the differential pressure across the clapper, tripping the valve sooner than it would have tripped on its own. {note}

−

−### A quick-opening device shall be provided where required by NFPA 13 — that is, where the calculated water delivery time without a QOD exceeds 60 seconds for a 750-gallon system, or where the Owner requires faster water delivery for property protection.

−

−```datasheet

−label: Quick-Opening Device

−type: radio

−options:

− - "Not required — system volume below threshold and water delivery time met"

− - "Accelerator — listed for dry-pipe valve manufacturer"

− - "Nitrogen inerting in lieu of accelerator (NFPA 13 alternative)"

− - "Accelerator and nitrogen inerting (combined for largest systems)"

−default: "Not required — system volume below threshold and water delivery time met"

−```

−

−### The accelerator shall be installed strictly per the dry-pipe valve manufacturer's instructions.

−

−### Mixing accelerator and valve from different manufacturers is not permitted unless the combination is independently listed, because the accelerator and the dry-pipe valve are listed together as a system.

−

−### The accelerator shall include an anti-flood device to prevent water from entering the accelerator pilot line after the valve trips, which would otherwise damage the accelerator internals and produce a costly post-trip service event.

−

−# Air Supply {toc}

−

−## Air Compressor {toc}

−

−### Two compressor arrangements are recognized: a dedicated compressor that serves only the dry-pipe system through an air maintenance device, and a tank-mounted or plant compressor that serves multiple loads with the dry-pipe system connection regulated through an air maintenance device. {note}

−

−### The dedicated compressor arrangement is preferred for new construction because it isolates the dry-pipe system from plant air contamination and pressure fluctuations. {note}

−

−### Where the supervisory gas is air, an air compressor shall be provided to maintain the system at the required air pressure.

−

−```datasheet

−label: Air Supply Type

−type: radio

−options:

− - "Dedicated air compressor — tank-mounted, single dry-pipe system"

− - "Dedicated air compressor — tankless, single dry-pipe system"

− - "Plant air through listed air maintenance device"

− - "Nitrogen generator — air compressor with N2 membrane or PSA module"

−default: "Dedicated air compressor — tank-mounted, single dry-pipe system"

−```

−

−### The compressor shall be capable of restoring the system from atmospheric pressure to the required operating pressure within 30 minutes for systems up to 750 gallons, and within 60 minutes for larger systems, as permitted by NFPA 13.

−

−```datasheet

−label: Air Compressor Restoration Time Requirement

−type: range

−unit: min

−options:

− min: 15

− max: 60

− setpoints: [15, 30, 45, 60]

−default: 30

−```

−

−### The compressor shall be sized by the air maintenance device manufacturer's recommendation based on system volume, expected leakage rate, and required restoration time.

−

−```datasheet

−label: Air Compressor Sizing Basis

−type: select

−options:

− - "Manufacturer sizing per system volume"

− - "Per NFPA 13 Table A.16.7.4.1 (sizing tables)"

− - "Engineered sizing for combined-system loads"

−default: "Manufacturer sizing per system volume"

−```

−

−### The air maintenance device shall be listed and, where FM compliance is required, approved to FM 2024.

−

−### The air maintenance device shall limit the rate of air introduction to the system so that a small leak does not mask a larger leak, because a system with oversized restoration capacity can fill faster than it can lose air through small leaks, allowing leaks to persist undetected until a major event reveals them.

−

−## Nitrogen Generator {toc}

−

−### A nitrogen generator consists of an air compressor, a moisture and oil filter train, and a nitrogen separation module (either a hollow-fiber membrane or a pressure-swing adsorption (PSA) module) that strips oxygen from compressed air to produce a nitrogen-enriched gas at the listed purity level. {note}

−

−### Nitrogen inerting eliminates the oxygen that drives internal corrosion in dry-pipe systems and is recognized by NFPA 13 as a corrosion-mitigation method. {note}

−### It is also recognized as a quick-opening alternative for system-volume purposes in some configurations, because the absence of oxygen alters the gas-discharge dynamics during a trip. {note}

−### Nitrogen generators are increasingly the default specification for new dry-pipe systems in cold-storage warehouses, healthcare facilities, and other long-life or critical assets. {note}

−

−### Where a nitrogen generator is provided, the purge cycle method shall be specified to maintain the required nitrogen purity at the most remote sprinkler.

−

−```datasheet

−label: Nitrogen Generator Purge Cycle

−type: radio

−options:

− - "Continuous purge from generator to maintain purity"

− - "Periodic timed purge at automatic vent"

− - "Initial purge only at commissioning"

−default: "Periodic timed purge at automatic vent"

−```

−

−### Where the supervisory gas is nitrogen, a listed nitrogen generator shall be provided.

−

−```datasheet

−label: Nitrogen Generator Type

−type: radio

−options:

− - "Not applicable — air supervision"

− - "Membrane-type nitrogen generator"

− - "Pressure-swing adsorption (PSA) nitrogen generator"

−default: "Not applicable — air supervision"

−```

−

−### The generator shall produce a gas of at least 98 percent nitrogen at the dry-pipe valve.

−

−### The system shall be purged of residual air during commissioning so that the nitrogen purity at the most remote sprinkler also reaches the listed level.

−

−```datasheet

−label: Nitrogen Purity at Sprinkler

−type: range

−unit: '%'

−options:

− min: 90

− max: 99

− setpoints: [90, 95, 98, 99]

−default: 98

−```

−

−## Air Leakage Limit {toc}

−

−### A leaky system masks itself with frequent compressor cycling that conceals the underlying defect; the air-leakage test is the only reliable way to verify joint integrity in an air-pressurized system. {note}

−

−### NFPA 13 requires that the system not lose more than 1.5 psi of air or nitrogen pressure over 24 hours after the system is brought to operating pressure and isolated from the supply.

−

−```datasheet

−label: Air Leakage Test Limit

−type: radio

−unit: psi/24 hr

−options:

− - "1.5 psi per 24 hours (NFPA 13)"

−default: "1.5 psi per 24 hours (NFPA 13)"

−```

−

−### The Contractor shall conduct an air-leakage test at acceptance and shall document the result.

−

−### Leakage exceeding 1.5 psi per 24 hours indicates joint, fitting, or sprinkler thread defects that shall be located and corrected before the system is accepted.

−

−# Piping Materials {toc}

−

−## Steel Pipe {toc}

−

−### ASTM A795 is the purpose-written standard for fire protection piping and is the preferred specification because it was developed specifically for sprinkler service and includes both black and galvanized options. {note}

−### For dry-pipe systems the galvanized variant is strongly preferred over the black variant unless the system is also nitrogen-inerted, because internal corrosion in cycled wet-dry environments is significantly more aggressive than in continuously wet systems. {note}

−

−### Steel pipe shall conform to ASTM A795 or ASTM A53, as applicable.

−

−```datasheet

−label: Steel Pipe Standard

−type: radio

−options:

− - "ASTM A795 (galvanized) — preferred for dry-pipe"

− - "ASTM A795 (black) — only with nitrogen inerting"

− - "ASTM A53 (galvanized)"

− - "ASTM A53 (black) — only with nitrogen inerting"

−default: "ASTM A795 (galvanized) — preferred for dry-pipe"

−```

−

−### Steel pipe used in dry-pipe systems shall be Schedule 40 for threaded joints in sizes 3 in. and smaller, and shall be Schedule 10 (listed for dry-system service) or Schedule 40 for grooved or welded joints.

−

−```datasheet

−label: Steel Pipe Schedule

−type: radio

−options:

− - "Schedule 40 throughout"

− - "Schedule 10 listed for dry-pipe service, 2 in. and larger; Schedule 40 for 1-1/2 in. and smaller"

− - "Schedule 10 listed for dry-pipe service throughout, grooved joints"

−default: "Schedule 10 listed for dry-pipe service, 2 in. and larger; Schedule 40 for 1-1/2 in. and smaller"

−```

−

−### The Contractor shall confirm that the specific pipe product carries the dry-system listing from the manufacturer, because not all Schedule 10 pipe is listed for dry-pipe service.

−

−### Thinner-wall pipe in a cycled wet-dry environment corrodes through the wall faster than thicker-wall pipe, which is why pipe manufacturers test and list specific products for the dry-pipe duty. {note}

−

−### The Contractor shall not thread Schedule 10 pipe, because threading Schedule 10 violates the pipe listing and is a common and serious field error.

−

−### CPVC pipe shall not be used in dry-pipe systems, because CPVC is listed only for wet-pipe service and the cycled drying and the impact of compressed air discharge during a trip exceed the CPVC pipe rating.

−

−## Fittings {toc}

−

−```datasheet

−label: Fitting Standard

−type: checkbox

−options:

− - "ASME B16.3 malleable iron threaded"

− - "ASME B16.9 wrought buttwelding"

− - "ASME B16.11 forged socket-welding or threaded"

− - "ASME B16.5 flanges"

− - "ANSI/AWWA C606 grooved couplings"

− - "ASTM A234 wrought carbon steel"

−default: "ASME B16.3 malleable iron threaded"

−```

−

−### Steel fittings shall be listed for fire protection service and shall be compatible with the joining method and pipe schedule used.

−

−### Malleable iron threaded fittings shall be used with threaded Schedule 40 pipe.

−

−### Wrought carbon steel buttwelding fittings conforming to ASTM A234 and ASME B16.9 shall be used with welded joints.

−

−### Grooved mechanical couplings and fittings shall be listed and shall conform to ANSI/AWWA C606.

−

−### Forged fittings conforming to ASME B16.11 are permitted for socket-welding and threaded joints.

−

−### Flanges where used shall conform to ASME B16.5.

−

−### Galvanized fittings shall be used with galvanized pipe, because mixing black fittings with galvanized pipe defeats the corrosion protection at the threaded joint, which is the most corrosion-prone location in the system.

−

−## Joining Methods {toc}

−

−```datasheet

−label: Primary Joining Method

−type: select

−options:

− - "Threaded (Schedule 40 only, 3 in. and smaller)"

− - "Grooved mechanical coupling (listed for dry-system service, 1 in. and larger)"

− - "Welded (Schedule 40, 1 in. and larger)"

− - "Grooved mains / threaded branch lines"

−default: "Grooved mains / threaded branch lines"

−```

−

−### Threaded joints shall use listed fire protection thread sealant applied to male threads only in accordance with the sealant manufacturer's instructions.

−

−### Polytetrafluoroethylene (PTFE) tape is not permitted as the sole thread sealant on fire protection threaded joints.

−

−### Threaded joints in dry-pipe systems shall be assembled with particular care because air-tightness — not just water-tightness — is required to meet the 1.5 psi per 24 hour leakage limit; minor thread imperfections that would seal water under pressure may leak air at the same pressure.

−

−### Grooved mechanical couplings shall be either rigid or flexible as required by NFPA 13 and the seismic design.

−

−### Coupling gasket compounds shall be compatible with the supervisory gas — standard EPDM gaskets are acceptable for air and nitrogen service.

−

−### Coupling installation torque shall be confirmed at every joint.

−

−### Welding shall be performed by welders qualified in accordance with AWS D10.12.

−

−### The weld joint shall be visually inspected for full penetration.

−

−### The weld area on galvanized pipe shall be repaired with cold-galvanizing compound after welding because the heat affected zone has lost its zinc coating.

−

−# Sprinklers {toc}

−

−## Sprinkler Types {toc}

−

−### A dry-pendent sprinkler is a specialized sprinkler with an extended barrel and an internal seal at the inlet, allowing the sprinkler to be installed pendent below a ceiling while keeping the supply piping above the ceiling in the heated space, and the barrel running through the unheated cavity. {note}

−

−### All sprinklers shall be listed to UL 199 and shall be installed in accordance with their listing and the installation requirements of NFPA 13.

−

−### Sprinklers shall not be modified in any way, including bending of the deflector, painting, or application of any coating, after leaving the factory.

−

−### Factory-applied coatings provided by the manufacturer for corrosive environments are permitted; field-applied paint or coatings over sprinklers are prohibited.

−

−### Upright sprinklers shall be the default for exposed dry-pipe piping in mechanical rooms, parking garages, and warehouse spaces because their orientation prevents water from collecting in the sprinkler body and freezing.

−

−```datasheet

−label: Sprinkler Orientation

−type: select

−drawing_ref: true

−options:

− - "Upright (exposed piping)"

− - "Dry-pendent (heated supply, unheated cavity)"

− - "Dry-sidewall (heated supply, unheated room)"

−default: "Upright (exposed piping)"

−```

−

−### Standard pendent sprinklers shall not be installed on dry-pipe systems because residual water at the sprinkler will freeze and damage the sprinkler.

−

−### Where pendent installation is required for architectural or coverage reasons, listed dry-pendent (or dry-sidewall) sprinklers shall be used.

−

−### The dry-pendent or dry-sidewall barrel length shall be sized so that the inlet seal sits in the warm side of the insulated separation; consult the manufacturer's barrel length tables.

−

−```datasheet

−label: Dry-Pendent / Dry-Sidewall Barrel Length

−type: select

−unit: in

−drawing_ref: true

−options:

− - "4 in."

− - "6 in."

− - "8 in."

− - "10 in."

− - "12 in."

− - "18 in."

− - "24 in."

− - "Not applicable — upright only"

−default: "Not applicable — upright only"

−```

−

−## Thermal Response {toc}

−

−### The NFPA 13 design density and area tables for dry-pipe systems are based on standard response sprinklers; mixing quick response sprinklers with a standard-response design produces unpredictable performance. {note}

−

−### Sprinklers are classified by thermal response as standard response or quick response based on the response time index (RTI) of the thermal element. {note}

−

−### Quick response sprinklers are not required in dry-pipe systems and shall not be used in dry-pipe systems unless specifically permitted by the listing and the hydraulic design accounts for the response timing.

−

−```datasheet

−label: Sprinkler Thermal Response

−type: radio

−options:

− - "Standard Response (RTI > 80 (m·s)^0.5) — required for dry-pipe"

− - "Quick Response — only with engineered analysis and AHJ approval"

−default: "Standard Response (RTI > 80 (m·s)^0.5) — required for dry-pipe"

−```

−

−## Temperature Ratings {toc}

−

−### Counterintuitively, dry-pipe systems in cold spaces still require careful sprinkler temperature selection — a sprinkler in a freezer warehouse experiences extremely low ambient temperatures but may be located near a defrost heater, light fixture, or ceiling-mounted product that produces local heating well above the freezer setpoint.

−

−```datasheet

−label: Sprinkler Temperature Rating — General Areas

−type: select

−options:

− - "Ordinary (135°F–170°F) — ambient up to 100°F"

− - "Intermediate (175°F–225°F) — ambient 101°F–150°F"

− - "High (250°F–300°F) — ambient 151°F–225°F"

−default: "Ordinary (135°F–170°F) — ambient up to 100°F"

−```

−

−### Sprinklers shall be selected for the temperature rating appropriate to the maximum expected ambient temperature at the ceiling level per NFPA 13 Table 8.3.2.1.

−

−### Ordinary temperature rating (135°F to 170°F) is appropriate for most dry-pipe applications, including freezer warehouses where ambient is below 32°F.

−

−### Intermediate temperature rating (175°F to 225°F) is required at locations near heat-emitting equipment in any space.

−

−### The Contractor shall verify temperature rating for sprinklers near unit heaters, radiant tubes, and ceiling-mounted defrost equipment.

−

−## K-Factor {toc}

−

−### The K-factor of a sprinkler determines the relationship between flow (Q in gpm) and pressure (P in psi) per the equation Q = K√P. {note}

−### Standard spray sprinklers are available in K-factors of 2.8, 4.2, 5.6, 8.0, 11.2, 14.0, and higher per NFPA 13. {note}

−### The K-5.6 sprinkler is the most widely used standard commercial sprinkler in dry-pipe applications. {note}

−

−### Larger K-factors may be selected for dry-pipe applications where the design density and area combine to require a higher flow per sprinkler than K-5.6 can deliver at acceptable pressures.

−

−```datasheet

−label: Sprinkler K-Factor

−type: select

−drawing_ref: "sprinkler schedule"

−options:

− - "K-5.6 (17/32 in. orifice, standard commercial)"

− - "K-8.0 (large orifice)"

− - "K-11.2 (extra large orifice)"

− - "K-14.0"

−default: "K-5.6 (17/32 in. orifice, standard commercial)"

−```

−

−## Finish {toc}

−

−```datasheet

−label: Sprinkler Finish

−type: select

−drawing_ref: true

−options:

− - "Natural brass"

− - "Chrome"

− - "White paint (factory-applied)"

− - "Wax-coated (corrosive atmospheres)"

− - "Lead-coated (corrosive atmospheres)"

−default: "Natural brass"

−```

−

−### Sprinkler finish shall be as scheduled for each area on the drawings.

−

−## Spare Sprinklers {toc}

−

−```datasheet

−label: Spare Sprinkler Cabinet Quantity

−type: select

−options:

− - "6 sprinklers (≤300 heads installed)"

− - "12 sprinklers (301–1,000 heads installed)"

− - "24 sprinklers (>1,000 heads installed)"

−default: "6 sprinklers (≤300 heads installed)"

−```

−

−### The Contractor shall provide a cabinet of spare sprinklers and one sprinkler wrench, mounted in the dry-pipe valve room or mechanical room, in accordance with NFPA 13.

−

−### The cabinet shall contain at minimum six sprinklers for systems with up to 300 sprinklers, 12 sprinklers for 300 to 1,000 sprinklers, or 24 sprinklers for systems with over 1,000 sprinklers.

−

−### Spare sprinklers shall represent each type, orifice size, temperature rating, and finish installed — including spare dry-pendent and dry-sidewall sprinklers where these are installed in the system.

−

−# Drainage {toc}

−

−## Pipe Pitch {toc}

−

−### The pitch is the primary mechanism by which residual water — from a hydrostatic test, a trip, condensation, or a partial trip-and-reset — is removed from the system. {note}

−### A dry-pipe system with sagging pipe or insufficient pitch will retain residual water at low spots, where the water freezes during the next cold cycle, ruptures the pipe, and floods the building when the rupture thaws. {note}

−

−### Dry-pipe system piping shall be pitched to drain back to the dry-pipe valve or to auxiliary drains (drum drips) at low points.

−

−### NFPA 13 requires minimum pitch of 1/2 in. per 10 ft for branch lines and 1/4 in. per 10 ft for mains in steel-pipe systems.

−

−```datasheet

−label: Minimum Branch Line Pitch

−type: range

−unit: in per 10 ft

−options:

− min: 0.5

− max: 2.0

− setpoints: [0.5, 1.0, 1.5, 2.0]

−default: 0.5

−```

−

−```datasheet

−label: Minimum Main Pitch

−type: range

−unit: in per 10 ft

−options:

− min: 0.25

− max: 1.0

− setpoints: [0.25, 0.5, 0.75, 1.0]

−default: 0.25

−```

−

−### The Contractor shall verify pitch at every section of pipe during installation using a level.

−

−### Pitch deficiencies discovered after ceiling closure are extremely expensive to correct. {note}

−

−## Auxiliary Drains (Drum Drips) {toc}

−

−### A drum drip consists of a vertical short pipe with an isolation valve at the top and a drain valve at the bottom, separated by a small reservoir (the "drum") that collects accumulated water. {note}

−### To drain, the operator closes the upper valve, opens the lower valve to discharge collected water, closes the lower valve, and opens the upper valve again to restore system continuity. {note}

−

−### Auxiliary drains, commonly called drum drips, shall be provided at every trapped section of pipe where water cannot drain back to the main drain by gravity.

−

−```datasheet

−label: Auxiliary Drain (Drum Drip) Configuration

−type: radio

−drawing_ref: "pitch and drainage plan"

−options:

− - "Single 1 in. drum drip at each trapped low point"

− - "Two-valve drum drip assembly with isolation and drain valves"

−default: "Two-valve drum drip assembly with isolation and drain valves"

−```

−

−### Drum drips shall be located so that they can be reached for routine drainage.

−

−### The Contractor shall coordinate drum drip locations with the architect to provide access doors or accessible plenums at every drum drip.

−

−```datasheet

−label: Drum Drip Access Provisions

−type: select

−drawing_ref: true

−options:

− - "All drum drips in accessible mechanical space"

− - "Access panels provided at each drum drip"

− - "Some drum drips in plenums — coordinate ceiling access"

−default: "Access panels provided at each drum drip"

−```

−

−### Each drum drip shall be identified with a permanent sign indicating its location relative to the dry-pipe valve and the seasonal drainage schedule.

−

−### NFPA 25 requires drum drips to be drained as part of seasonal pre-winter maintenance — typically in the autumn before the first freeze — and after any system trip.

−

−### Missed drum drip drainage is the single most common cause of dry-pipe system freeze damage. {note}

−

−## Main Drain {toc}

−

−```datasheet

−label: Main Drain Discharge Location

−type: select

−options:

− - "Floor drain — interior heated valve room"

− - "Exterior discharge at grade"

− - "Discharge to storm system"

−default: "Floor drain — interior heated valve room"

−```

−

−### A main drain valve of a size not smaller than 2 in. shall be provided at the dry-pipe valve assembly to allow the system to be drained completely for maintenance.

−

−### The main drain discharge shall terminate at a location where water can be discharged safely without causing property damage.

−

−### The main drain discharge shall include freeze protection where the discharge piping passes through unheated space.

−

−# Fire Department Connections {toc}

−

−## FDC Location and Accessibility {toc}

−

−### In most jurisdictions the AHJ will specify that the FDC be within 100 ft of a fire hydrant and clearly visible and accessible from the street or apparatus access road. {note}

−

−### A fire department connection (FDC) shall be provided for the dry-pipe sprinkler system in accordance with NFPA 13 and the International Fire Code.

−

−### The FDC shall be located on the exterior of the building at a point accessible to fire apparatus and approved by the Authority Having Jurisdiction.

−

−### The Contractor shall confirm the required FDC location with the AHJ prior to installation.

−

−### The FDC piping for a dry-pipe system shall include an automatic ball drip on the supply piping between the dry-pipe valve and the FDC to drain any water that enters the FDC piping during cold weather.

−

−### The FDC inlets and check valves shall be installed so that water from a fire department supply enters the system downstream of the dry-pipe valve clapper, bypassing the supervisory air.

−

−### The check valve at each FDC inlet shall prevent back-pressurization of the FDC piping and prevent loss of system air through the FDC during normal operation.

−

−## FDC Type and Size {toc}

−

−```datasheet

−label: FDC Type

−type: radio

−options:

− - "Siamese (two 2-1/2 in. inlets)"

− - "Single 4 in. LDH (large diameter hose) inlet"

− - "Siamese plus one 4 in. LDH inlet"

−default: "Siamese (two 2-1/2 in. inlets)"

−```

−

−```datasheet

−label: FDC Inlet Thread

−type: radio

−options:

− - "National Standard Thread (NST / NH)"

− - "Local fire department thread — confirm with AHJ"

−default: "National Standard Thread (NST / NH)"

−```

−

−### The FDC type, size, and inlet thread shall be as scheduled and shall be confirmed with the AHJ.

−

−## FDC Identification Signage {toc}

−

−### The "DRY" designation alerts the responding fire department to the delayed water delivery of a dry-pipe system, which affects how they will pressurize the FDC during operations. {note}

−

−### The FDC shall be identified with a sign reading "AUTO SPKR — DRY" in letters not smaller than 1 in. in height, in accordance with NFPA 13.

−

−```datasheet

−label: FDC Identification Sign

−type: radio

−options:

− - "\"AUTO SPKR — DRY\" per NFPA 13"

− - "\"AUTO SPKR — DRY\" plus zone identification"

−default: "\"AUTO SPKR — DRY\" per NFPA 13"

−```

−

−### Where the building has multiple FDCs serving separate sprinkler systems (some wet, some dry), each FDC shall identify the zone and the system type.

−

−# Alarm and Supervisory Devices {toc}

−

−## Waterflow Alarm {toc}

−

−### The pressure switch is mounted on the alarm port of the dry-pipe valve and operates when water flows from the supply through the alarm port. {note}

−### Unlike a wet-pipe waterflow vane switch, the dry-pipe alarm pressure switch signals essentially instantaneously when the valve trips because water under full supply pressure reaches the alarm port within seconds of the clapper opening. {note}

−### Water motor gongs are particularly valuable for dry-pipe systems serving outbuildings or detached structures where the main fire alarm notification appliances may be remote.

−

−```datasheet

−label: Waterflow Alarm Devices

−type: checkbox

−options:

− - "Electric alarm pressure switch connected to fire alarm system"

− - "Water motor gong (exterior, hydraulic)"

− - "Both — pressure switch and water motor gong"

−default: "Electric alarm pressure switch connected to fire alarm system"

−```

−

−### The dry-pipe valve shall be equipped with a listed waterflow alarm pressure switch that signals the fire alarm control panel when the valve trips, in accordance with NFPA 13 and NFPA 72.

−

−### A water motor gong may also be provided for local audible alarm without electrical power, in addition to the electric alarm pressure switch.

−

−## Low-Pressure Supervisory Switch {toc}

−

−### The low-pressure signal indicates a system leak that requires investigation; persistent low-pressure signals may also indicate an incipient trip and shall be treated as an urgent maintenance event.

−

−```datasheet

−label: Pressure Supervisory Signals

−type: checkbox

−options:

− - "Low air or nitrogen pressure switch"

− - "High air or nitrogen pressure switch"

−default: "Low air or nitrogen pressure switch"

−```

−

−### The dry-pipe valve shall be equipped with a listed low-pressure supervisory switch that signals the fire alarm control panel when the air or nitrogen pressure falls below the manufacturer's specified minimum (typically 5 to 10 psi below the normal operating pressure).

−

−### Some dry-pipe systems also include a high-pressure supervisory switch that signals when the air pressure exceeds the maximum acceptable value, indicating a malfunctioning air maintenance device or a pressure regulator failure that could mask an underlying leak or cause delayed valve operation.

−

−## Hydraulic and Water Delivery Design Information Signs {toc}

−

−### A hydraulic design information sign shall be permanently affixed at the dry-pipe valve in accordance with NFPA 13, stating the design density, design area (with the 30 percent dry-pipe increase), required flow and pressure at the base of the riser, hose stream demand, total water demand, and K-factor.

−

−### Dry-pipe systems shall display a water delivery design information sign stating the calculated system volume, the calculated water delivery time, and the test result from the water delivery acceptance test.

−

−# Hangers and Seismic Bracing {toc}

−

−## Hanger Design and Spacing {toc}

−

−```datasheet

−label: Hanger Attachment to Structure

−type: select

−options:

− - "C-clamp to steel flange"

− - "Beam clamp (side beam clip)"

− - "Through-bolt in concrete"

− - "Concrete insert (cast)"

− - "Power-driven fastener in concrete (listed)"

− - "Powder-actuated fastener in steel deck"

− - "Threaded rod from beam above"

−default: "Threaded rod from beam above"

−```

−

−### Hangers shall be listed for fire protection use and shall be installed in accordance with NFPA 13 Chapter 17 and the hanger manufacturer's listing.

−

−### Hangers shall be capable of supporting five times the weight of the water-filled pipe plus 250 lb at each point of support.

−

−### Hanger calculations for dry-pipe systems shall use the water-filled weight, not the air-filled weight, because the pipe is filled with water during hydrostatic testing and after every trip.

−

−### Steel pipe shall be supported at intervals not exceeding those specified in NFPA 13: 1-1/4 in. and smaller at 12 ft maximum spacing; 1-1/2 in. at 15 ft; 2 in. and larger at not more than 15 ft for standard hanger loads.

−

−### Hangers shall be located near each sprinkler and within 12 in. of every branch line end.

−

−### The Contractor shall not omit sprinkler-proximity hangers because of interference with other trades.

−

−## Seismic Bracing {toc}

−

−### Seismic design for dry-pipe systems follows the same provisions as for wet-pipe systems with one important addition: dry-pipe systems are more sensitive to joint failure during seismic events because the resulting loss of air pressure trips the valve and floods the system. {note}

−

−### Where the building is located in a Seismic Design Category (SDC) C, D, E, or F as defined by ASCE 7 and the IBC, lateral and longitudinal seismic bracing shall be provided for the sprinkler system in accordance with NFPA 13 Chapter 18.

−

−```datasheet

−label: Seismic Bracing Required

−type: radio

−options:

− - "No — SDC A or B"

− - "Yes — SDC C"

− - "Yes — SDC D, E, or F (full bracing per NFPA 13 Chapter 18)"

−default: "No — SDC A or B"

−```

−

−```datasheet

−label: Seismic Design Category

−type: select

−drawing_ref: true

−options:

− - "A"

− - "B"

− - "C"

− - "D"

− - "E"

− - "F"

−default: "B"

−```

−

−### Flexible couplings at the prescribed locations are essential.

−

−```datasheet

−label: Flexible Couplings at Seismic Brace Locations

−type: radio

−options:

− - "Not required — SDC A or B"

− - "Required within 6 in. of each brace on 2-1/2 in. and larger pipe"

− - "Required — exact spacing per seismic calculations"

−default: "Not required — SDC A or B"

−```

−

−# Installation {toc}

−

−## Pipe Routing and Coordination {toc}

−

−### For dry-pipe systems, deviations from the reviewed working drawings are particularly consequential because pipe routing changes affect system volume, water delivery time, and the location and count of auxiliary drains. {note}

−

−### Working drawings approved by the AHJ govern the routing, sizing, and arrangement of all sprinkler piping.

−

−### Deviations from the reviewed working drawings require either a revised submittal or written approval from the Engineer of Record and the AHJ.

−

−### The Contractor shall not field-route dry-pipe piping without engineering review.

−

−### Sprinkler piping shall be routed to maintain the required minimum pitch.

−

−### Where structural elements, HVAC ducts, or other obstructions force the piping to deviate from a continuous fall, an auxiliary drain shall be provided at the resulting low point.

−

−## Cutting and Fabrication {toc}

−

−### Pipe shall be cut square and all burrs removed before jointing.

−

−### Threaded pipe shall be reamed after threading to remove the internal burr, because a cutting burr left inside the pipe impedes flow and accelerates corrosion.

−

−### Grooved pipe ends shall be roll-grooved or cut-grooved to the coupling manufacturer's dimension specifications.

−

−## Protection During Construction {toc}

−

−### Dry-pipe systems are particularly vulnerable to debris because the dry-pipe valve trim, accelerator, and air maintenance device contain small orifices that can be obstructed by particulates that pass through the dry-pipe valve during a trip. {note}

−

−### Dry-pipe piping shall be protected against contamination during construction.

−

−### All open pipe ends shall be capped when work is not in progress to prevent the introduction of debris, rodents, insects, and construction materials.

−

−## Field-Cut Pipe Coating {toc}

−

−### Failure to touch up field-cut galvanized pipe creates corrosion initiation sites at the threads, which is exactly the area most prone to trapped water and oxygen exposure. {note}

−

−### Galvanized pipe that is field-cut, threaded, or welded shall have the heat-affected or cut area touched up with a listed cold-galvanizing compound to restore the corrosion protection.

−

−### The Contractor shall include cold-galvanizing compound in the standard tool kit and shall apply it as a routine step during pipe installation.

−

−# Acceptance Testing {toc}

−

−## Flushing {toc}

−

−### The system piping shall be flushed before sprinklers are installed, in accordance with NFPA 13 and NFPA 24.

−

−### Flushing shall be performed at a flow velocity adequate to remove debris from the installation.

−

−### The flushing discharge shall be directed to an approved location and shall continue until the effluent runs clear.

−

−### The Contractor shall document the flushing by recording the date, the pipe sections flushed, the flow rate used, and the duration.

−

−## Hydrostatic Pressure Test {toc}

−

−```datasheet

−label: Hydrostatic Test Pressure

−type: range

−unit: psi

−options:

− min: 200

− max: 400

− setpoints: [200, 250, 300, 350, 400]

−default: 200

−```

−

−```datasheet

−label: Hydrostatic Test Duration

−type: radio

−unit: hours

−options:

− - "2 hours"

−default: "2 hours"

−```

−

−### All piping shall be hydrostatically tested at 200 psi for 2 hours with no pressure loss at the test gauge and no visible leaks, in accordance with NFPA 13.

−

−### Where system working pressure exceeds 150 psi, the test pressure shall be the system working pressure plus 50 psi.

−

−### The hydrostatic test shall be conducted after all piping is complete, after flushing, and before ceilings are closed.

−

−### After the hydrostatic test is complete and witnessed, the system shall be thoroughly drained — including every auxiliary drain — before being placed in dry service.

−

−### The Contractor shall confirm that every drum drip is fully drained and operating before the system is placed in dry service.

−

−## Air Pressure Test {toc}

−

−### The air test detects joint leaks that may have sealed under water pressure but leak air; this is a non-trivial number of joints in any new system.

−

−```datasheet

−label: Air Test Pressure

−type: range

−unit: psi

−options:

− min: 40

− max: 60

− setpoints: [40, 50, 60]

−default: 40

−```

−

−```datasheet

−label: Air Test Duration

−type: radio

−unit: hours

−options:

− - "24 hours"

−default: "24 hours"

−```

−

−```datasheet

−label: Air Test Allowable Pressure Loss

−type: radio

−unit: psi

−options:

− - "1.5 psi (NFPA 13)"

−default: "1.5 psi (NFPA 13)"

−```

−

−### In addition to the hydrostatic test, the system shall be air-tested at 40 psi for 24 hours with a pressure loss not exceeding 1.5 psi at the end of the test, in accordance with NFPA 13.

−

−### The air test shall be conducted after the system is drained from the hydrostatic test and before the system is placed in service.

−

−### Leaks shall be located by soap-bubble testing or ultrasonic leak detection and corrected before retest.

−

−## Dry-Pipe Valve Trip Test {toc}

−

−### The trip test confirms that the valve operates as listed and that the calculated water delivery time is achieved in practice. {note}

−

−### The dry-pipe valve shall be trip-tested by opening the inspector's test valve at the most remote point of the system and timing the interval until water discharges from the inspector's test connection.

−

−### Trip tests shall be performed both with the quick-opening device (where installed) in service and, where required by the AHJ, with the QOD bypassed.

−

−### The water delivery time at the trip test shall not exceed 60 seconds from opening of the inspector's test valve to water discharge, in accordance with NFPA 13.

−

−```datasheet

−label: Maximum Water Delivery Time at Trip Test

−type: radio

−unit: seconds

−options:

− - "60 seconds (NFPA 13)"

−default: "60 seconds (NFPA 13)"

−```

−

−### The trip test result shall be recorded on the Contractor's Material and Test Certificate.

−

−### Where the field-measured delivery time exceeds the calculated value, the cause shall be investigated and corrected; common causes include partially obstructed orifices in the dry-pipe valve trim, insufficient pipe pitch causing air entrapment, or undersized air supply.

−

−## Alarm Device Test {toc}

−

−### The waterflow alarm pressure switch shall be tested as part of the trip test by confirming that the fire alarm control panel receives the alarm signal when the valve trips.

−

−### The valve supervisory switches for all supervised control valves shall be tested by partially closing each valve and confirming that the fire alarm control panel receives the supervisory signal within two turns of the handwheel.

−

−### The low-pressure supervisory switch shall be tested by bleeding air pressure from the system through the inspector's test valve and confirming the supervisory signal at the manufacturer's specified pressure.

−

−## Main Drain Test {toc}

−

−```datasheet

−label: Main Drain Static Pressure at Acceptance

−type: range

−unit: psi

−drawing_ref: true

−options:

− min: 20

− max: 200

− setpoints: [20, 40, 50, 60, 70, 80, 100, 120, 150, 175, 200]

−default: 70

−```

−

−```datasheet

−label: Main Drain Residual Pressure at Acceptance

−type: range

−unit: psi

−drawing_ref: true

−options:

− min: 10

− max: 180

− setpoints: [10, 20, 30, 40, 50, 60, 70, 80, 100, 120, 150, 180]

−default: 50

−```

−

−### The main drain shall be fully opened with all supply valves open and the static pressure and residual flowing pressure shall be recorded.

−

−### The flowing pressure at the main drain shall be documented and compared to the design water supply data.

−

−### The main drain test result shall be recorded on the Contractor's Material and Test Certificate and shall serve as the baseline for future NFPA 25 annual main drain tests.

−

−## Contractor's Material and Test Certificate {toc}

−

−### The Contractor shall complete and sign a Contractor's Material and Test Certificate for Aboveground Piping using the form provided in NFPA 13 Figure 29.1.1 or an equivalent form approved by the AHJ.

−

−### The certificate for a dry-pipe system shall document the same items as a wet-pipe system plus the dry-pipe valve trip test result with water delivery time; the air pressure test result with measured pressure loss over 24 hours; the air supply type and capacity; the quick-opening device (where installed) and its tested operation; and the verification of all auxiliary drain functionality.

−

−### The certificate shall be executed at the time of acceptance and retained permanently with the Owner's facility documentation.

−

−## Acceptance Inspection by AHJ {toc}

−

−### The AHJ's acceptance inspection for a dry-pipe system commonly includes witnessing the trip test and water delivery time measurement, verifying sprinkler placement, confirming hanger spacing and pipe pitch, testing alarm and supervisory devices, and reviewing the Contractor's Material and Test Certificate. {note}

−

−### The Contractor shall schedule an acceptance inspection with the Authority Having Jurisdiction after the system is complete, tested, and all deficiencies from preliminary inspections are corrected.

−

−### The system shall not be placed in service — and no certificate of occupancy shall be issued — until the AHJ has conducted the acceptance inspection and issued approval.

−

−# Ongoing Inspection, Testing, and Maintenance {toc}

−

−## NFPA 25 establishes mandatory intervals for inspecting system components, testing alarm devices, conducting main drain tests, performing the dry-pipe valve trip test, and servicing the air supply. {note}

−

−## The dry-pipe system shall be inspected, tested, and maintained throughout the life of the building in accordance with NFPA 25, current adopted edition.

−

−## Specific NFPA 25 requirements for dry-pipe systems shall include weekly or monthly inspection of the air or nitrogen pressure gauge and the dry-pipe valve enclosure heating; quarterly testing of waterflow and supervisory alarm devices; quarterly testing of low-pressure supervisory; annual full-flow trip test of the dry-pipe valve with the quick-opening device in service (and a separate test with the QOD bypassed in some jurisdictions); seasonal draining of every auxiliary drain (drum drip) before the first freeze and after every trip; 3-year internal inspection of the dry-pipe valve; and 5-year internal pipe assessment to check for obstruction, corrosion, and microbiological growth.

−

−## Dry-pipe systems shall be drained, dried, and refilled with fresh supervisory gas as part of the 3-year internal inspection.

−

−## The Owner shall maintain a service agreement with a qualified fire protection service contractor to perform NFPA 25 inspections and tests at the required intervals.

−

−```datasheet

−label: NFPA 25 Service Agreement

−type: radio

−options:

− - "Service agreement with qualified fire protection contractor"

− - "Owner-performed per NFPA 25 (qualified personnel required for testing)"

−default: "Service agreement with qualified fire protection contractor"

−```

−

−## Owner-performed inspections are permitted for certain visual tasks, but trip tests, internal valve inspections, and 5-year internal pipe assessments shall be performed by qualified service personnel.

−

−## Records of all inspections, tests, and maintenance activities shall be retained on-site and made available to the AHJ upon request.

−

−# Warranty {toc}

−

−```datasheet

−label: Installation Warranty Period

−type: select

−options:

− - "1 year from substantial completion"

− - "2 years from substantial completion"

−default: "1 year from substantial completion"

−```

−

−```datasheet

−label: Impairment Response Time

−type: radio

−unit: hours

−options:

− - "4 hours maximum for restoration or alternative protection"

− - "As required by AHJ impairment plan"

−default: "4 hours maximum for restoration or alternative protection"

−```

−

−## The Contractor shall warrant all materials and workmanship against defects for the project warranty period.

−

−## The warranty shall cover the complete installed system including pipe, fittings, hangers, seismic bracing, the dry-pipe valve, quick-opening device, air supply (compressor or nitrogen generator), alarm and supervisory devices, fire department connection, and all specialties.

−

−## Sprinklers carry individual manufacturer's limited warranties as stated in the manufacturer's product data; the Contractor shall pass through these warranties to the Owner.

−

−## The warranty period shall run from the date of substantial completion.

−

−## The Contractor shall correct, at no cost to the Owner, any leaks, failures, or deficiencies that arise from defective materials or workmanship during the warranty period.

−

−## Warranty service for dry-pipe systems shall include investigation of any persistent low-air-pressure alarms — a sign of joint leakage that may not have been present at acceptance but emerges as gaskets and joints age through the first heating and cooling cycles.

−

−## Any system impairment shall be handled in accordance with NFPA 25 impairment procedures, including prompt notification to the Owner, the monitoring station, the fire department, and the insurance carrier.

−

−## Returning an impaired dry-pipe system to service requires re-pressurization, drainage of any test water, and reset of the dry-pipe valve including verification of the intermediate chamber drain. {note}

−

−## The Contractor shall maintain the ability to restore impaired systems to full service within the time limits required by the AHJ and the Owner's insurance carrier.

+---

+title: Dry-Pipe Fire Sprinkler Systems

+category: Fire Protection

+description: >

+ When to use: Automatic dry-pipe sprinkler systems designed to NFPA 13, in which the piping downstream of a dry-pipe valve is held under supervisory air or nitrogen because the piping is exposed to freezing. Covers the decisions that exist only on a dry system: the dry-pipe valve and its trim, the quick-opening device, the supervisory gas source and its pressures, water delivery time, pitch and low-point drainage, the corrosion consequences of a wet-and-dry pipe interior, the provisions for piping in refrigerated spaces, and the trip test and 24-hour air leakage test that prove the installation.

+ Not intended for: The sprinkler-system family baseline of hazard classification, design density and area, water supply, sprinkler selection and temperature rating, control valves and their supervision, hangers and seismic bracing, hydrostatic testing, spare sprinklers, and warranty, which is carried by [[sync/wet-pipe-fire-sprinkler-systems]] and applies to systems furnished under this standard; pipe, fittings, and joining ([[sync/fire-protection-piping]]); pre-action and deluge systems, which also hold dry piping but admit water on a detection event ([[sync/pre-action-and-deluge-sprinkler-systems]]); standpipes ([[sync/standpipe-systems]]); fire pumps ([[sync/fire-pumps]]); fire department connections ([[sync/fire-department-connections]]); the fire alarm system that receives the waterflow and supervisory signals ([[sync/fire-alarm-systems]]); antifreeze systems and listed heat-tracing, which are freeze-protection alternatives that keep the piping wet; and storage-occupancy dry systems designed under the storage chapters of NFPA 13.

+---

+# Scope {toc}

+## This standard covers the dry-pipe valve, the quick-opening device, the supervisory gas supply and its pressures, water delivery time, pitch and drainage, interior corrosion mitigation, refrigerated-space provisions, and the acceptance tests specific to an automatic dry-pipe sprinkler system. {note}

+## In a dry-pipe system the piping downstream of the dry-pipe valve holds pressurized air or nitrogen instead of water. When a sprinkler opens, the supervisory gas escapes, the pressure differential that held the valve clapper closed collapses, and water enters the piping and flows to the open sprinkler after the gas ahead of it has been expelled. {note}

+## This standard is the dry-pipe layer over [[sync/wet-pipe-fire-sprinkler-systems]]. The family standard establishes how a sprinkler system is classified, sized, supplied, valved, supported, tested, spared, and warranted; this standard establishes what changes when the piping is dry: the valve that keeps it dry, the gas that supervises it, the delay before water arrives, the water that stays behind, and the tests that prove all of it. {note}

+## Dry-pipe systems furnished under this standard shall also comply with [[sync/wet-pipe-fire-sprinkler-systems]].

+## Where a requirement of this standard and a requirement of [[sync/wet-pipe-fire-sprinkler-systems]] address the same subject, the requirement of this standard shall govern.

+## Hazard classification, design density and area, water supply verification, sprinkler selection and temperature rating, control valve supervision, hangers and seismic bracing, hydrostatic testing, spare sprinklers, and warranty for systems furnished under this standard shall be as required by [[sync/wet-pipe-fire-sprinkler-systems]].

+## Pipe, fittings, and joints for systems furnished under this standard shall be as required by [[sync/fire-protection-piping]].

+## The extent of each dry-pipe system and the location of each dry-pipe valve shall be as indicated on [[drawing: the fire protection plans and riser diagram]].

+## Dry piping shall be used where the sprinkler piping cannot be maintained at or above 40°F (4°C), and wet piping shall be used elsewhere unless the Contract Documents direct otherwise.

+## Freezing exposure can also be met by an antifreeze system within the limits NFPA 13 sets for it, by listed heat-tracing with insulation, or by moving the piping into heated space. A dry system delays water, increases the design area, adds an air supply and a valve that need continual attention, and corrodes from the inside faster than a wet system; the alternatives avoid those costs where their own limits are not exceeded. {note}

+## The following are outside the scope of this standard: {note}

+- Pre-action and deluge systems, which hold dry piping but admit water on a detection signal rather than on the loss of supervisory pressure, and which are covered by [[sync/pre-action-and-deluge-sprinkler-systems]]

+- Antifreeze systems and listed heat-tracing, which protect piping against freezing while keeping it filled with liquid

+- Standpipes and hose connections, which are covered by [[sync/standpipe-systems]]

+- Fire pumps and the pressure they add to the supply, which are covered by [[sync/fire-pumps]]

+- The fire department connection, its check valve, and its automatic drain, which are covered by [[sync/fire-department-connections]]

+- The fire alarm control unit and the circuits that carry waterflow and supervisory signals, which are covered by [[sync/fire-alarm-systems]]

+- A plant compressed air system that supplies more than the dry-pipe systems, which is covered by [[sync/compressed-air-systems]]

+- Dry systems protecting storage occupancies under the storage chapters of NFPA 13, whose in-rack, density, and delivery provisions are outside this standard

+# Referenced Standards {toc}

+## Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.

+## Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.

+| Standard | Title |

+|----------|-------|

+| NFPA 13 | Standard for the Installation of Sprinkler Systems |

+| NFPA 25 | Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems |

+| NFPA 70 | National Electrical Code |

+| NFPA 72 | National Fire Alarm and Signaling Code |

+| UL 260 | Dry Pipe and Deluge Valves for Fire-Protection Service |

+| UL 753 | Alarm Accessories for Automatic Water-Supply Control Valves for Fire-Protection Service |

+| UL 1486 | Quick Opening Devices for Dry Pipe Valves for Fire-Protection Service |

+| FM Global Data Sheet 2-0 | Installation Guidelines for Automatic Sprinklers |

+| FM Global Data Sheet 2-1 | Corrosion in Automatic Sprinkler Systems |

+## Successive editions of NFPA 13 have changed the volume thresholds, the water delivery table, the nitrogen provisions, and the corrosion provisions that govern a dry system, so the edition adopted by the Authority Having Jurisdiction settles which rule applies to a given project. {note}

+## The Contractor shall confirm the edition of NFPA 13 adopted by the Authority Having Jurisdiction before beginning the working drawings.

+# Submittals {toc}

+## Action Submittals {toc}

+### The Contractor shall submit the following for the Engineer of Record's review and return, together with the submittals required by [[sync/wet-pipe-fire-sprinkler-systems]], before the dry-pipe valve, the supervisory gas supply, or the dry piping is procured:

+- Product data for the dry-pipe valve and its trim, identifying the listing, the size, the body and trim materials, the priming requirement, and the published trip pressure at each water supply pressure

+- Product data for the quick-opening device, where one is furnished, identifying the listing of the device with the dry-pipe valve it is installed on and the anti-flood provision

+- Product data for the supervisory gas source, identifying the compressor or nitrogen generator, its capacity, the air maintenance device, the dryer, the relief valve, and the electrical requirements

+- The calculated volume of each dry-pipe system

+- The water delivery time calculation for each system that is subject to the delivery time requirement, identifying the calculation method and the assumed supervisory pressure

+- The supervisory gas pressure calculation, stating the maximum water supply pressure at the valve, the published trip pressure, the margin applied, and the resulting normal pressure and low-pressure supervisory setpoint

+- The pitch and drainage plan, showing the direction of fall of every main and branch line, every trapped section, the volume of each trapped section, and the type and location of every auxiliary drain

+- Product data for the corrosion mitigation provided, identifying the pipe interior protection and, where nitrogen is used, the purity the generator produces and the purge provision

+- The refrigerated-space provisions, where dry piping serves a space held at or below 32°F, identifying the gas drying, the ice-plug inspection point, and the penetration seal

+```datasheet

+label: Action Submittals Required

+type: checkbox

+options:

+ - "Dry-pipe valve and trim product data"

+ - "Quick-opening device product data"

+ - "Supervisory gas source product data"

+ - "System volume calculation"

+ - "Water delivery time calculation"

+ - "Supervisory gas pressure calculation"

+ - "Pitch and drainage plan"

+ - "Corrosion mitigation product data"

+ - "Refrigerated-space provisions"

+default:

+ - "Dry-pipe valve and trim product data"

+ - "Supervisory gas source product data"

+ - "System volume calculation"

+ - "Supervisory gas pressure calculation"

+ - "Pitch and drainage plan"

+ - "Corrosion mitigation product data"

+```

+### The dry piping shall not be fabricated until the pitch and drainage plan has been reviewed and returned.

+### A dry system's routing is not free to change in the field the way a wet system's is. Every change moves the system volume, the delivery time, the trapped sections, and the auxiliary drain count together, so a run relocated around a duct after the plan was reviewed may have created a low point no one will drain. {note}

+## Closeout Submittals {toc}

+### The Contractor shall submit the following before the dry-pipe system is accepted, in addition to the closeout submittals required by [[sync/wet-pipe-fire-sprinkler-systems]]:

+- The trip test record for each dry-pipe valve, recording the supervisory pressure at the start, the pressure at which the valve tripped, the time from the opening of the inspector's test valve to the trip, and the time from the opening of the inspector's test valve to water at the test connection

+- The air leakage test record for each system, recording the starting pressure, the pressure after 24 hours, and the ambient temperature at each reading

+- The as-left supervisory gas pressure and the as-left low-pressure supervisory setpoint for each system

+- The nitrogen purity measured at the remote end of each system at the completion of purging, where nitrogen is the supervisory gas

+- An auxiliary drain register listing every auxiliary drain by location, type, and the section it drains

+- Operation and maintenance data covering the dry-pipe valve reset procedure, the supervisory gas supply, the auxiliary drain schedule, and the NFPA 25 test and inspection intervals that apply to a dry system

+- As-built drawings recording the installed pitch and drainage arrangement

+```datasheet

+label: Closeout Submittals Required

+type: checkbox

+options:

+ - "Trip test record"

+ - "Air leakage test record"

+ - "As-left supervisory pressure and setpoint"

+ - "Nitrogen purity record"

+ - "Auxiliary drain register"

+ - "Operation and maintenance data"

+ - "As-built drawings"

+default:

+ - "Trip test record"

+ - "Air leakage test record"

+ - "As-left supervisory pressure and setpoint"

+ - "Auxiliary drain register"

+ - "Operation and maintenance data"

+ - "As-built drawings"

+```

+### The auxiliary drain register is the document a future operator drains the system from. A drum drip that is not on the register is not drained before the first freeze, and the pipe above it is the pipe that splits. {note}

+# Quality Assurance {toc}

+## The individual who prepares the working drawings and the water delivery time calculation shall have prepared the design of not fewer than three dry-pipe systems that were accepted by an Authority Having Jurisdiction.

+## Where the parties disagree whether the designer's experience meets that requirement, the Engineer of Record shall make the initial determination.

+## The dry-pipe valve, the quick-opening device, the air maintenance device, and the nitrogen generator shall be listed for fire protection service.

+## The quick-opening device shall be listed for use with the dry-pipe valve on which it is installed, and a device and a valve from different manufacturers shall not be combined unless the combination is covered by a listing.

+## The device and the valve are tested and listed as a pair because the device works by sensing the rate of pressure drop and venting the intermediate chamber of one particular valve body. On a valve it was not listed with, the device can trip too early, too late, or flood itself. {note}

+## Where the Owner's property insurer requires it, the components named in this standard shall carry the insurer's approval in addition to the listing, in accordance with [[sync/wet-pipe-fire-sprinkler-systems]].

+# System Volume and Water Delivery Time {toc}

+## System Volume {toc}

+### The volume of each dry-pipe system shall be calculated from the working drawings and stated in the action submittal.

+### System volume is the quantity that sets every other dry-pipe decision. It fixes how much gas must escape before water reaches a sprinkler, how large the supervisory gas supply must be, whether the delivery time must be calculated and tested, and whether a quick-opening device is needed. {note}

+### The volume of a single dry-pipe system shall not exceed the volume indicated in the datasheet.

+```datasheet

+label: Maximum Volume of a Single Dry-Pipe System

+type: range

+unit: gal

+min: 500

+max: 3000

+setpoints: [500, 750, 1000, 1500, 2000, 3000]

+```

+### NFPA 13 exempts a system of not more than 500 gal, and a system of not more than 750 gal that has a quick-opening device, from the water delivery time requirement, and permits a larger system where its delivery time is demonstrated by calculation and confirmed by test. A project or an insurer may hold the volume below the calculated ceiling to keep the delivery time short or to keep the exemption, and a project protecting one large unheated volume may need the ceiling. {note}

+### Where the volume of a dry-pipe system as drawn would exceed the datasheet value, the Contractor shall subdivide the system into additional dry-pipe systems, each with its own dry-pipe valve, and shall report the subdivision to the Engineer of Record before the working drawings are submitted.

+## Water Delivery Time {toc}

+### Water shall reach the inspector's test connection at the most remote point of each dry-pipe system within the time indicated in the datasheet, measured from the full opening of the inspector's test valve with the system at its normal supervisory pressure.

+```datasheet

+label: Water Delivery Time Limit

+type: range

+unit: s

+derived: "the hazard classification selected for the protected area under the sprinkler family standard and the calculated system volume, applied to the dry system water delivery table of NFPA 13"

+min: 15

+max: 60

+setpoints: [15, 40, 45, 50, 60]

+default: derived

+```

+### The NFPA 13 delivery table assigns a shorter time to a higher hazard because the design area is already enlarged to cover the delay, and a fire in a high-hazard occupancy outgrows even the enlarged area if water is late. A system below the exempt volume has no delivery time requirement at all, and the limit indicated here applies only where the volume exceeds the exemption. {note}

+### Where the system volume exceeds the exemption, the delivery time shall be demonstrated by a calculation using a method acceptable to the Authority Having Jurisdiction, and the calculation shall assume the supervisory pressure the system will actually be held at.

+### A delivery calculation run at a lower supervisory pressure than the system is set to is optimistic, because the valve trips sooner from a lower starting pressure and less gas has to leave the pipe before water arrives. {note}

+### The calculated delivery time shall be confirmed by the trip test required under Testing, and the tested time shall govern acceptance.

+## Quick-Opening Device {toc}

+### The quick-opening device furnished at each dry-pipe valve shall be as indicated in the datasheet.

+```datasheet

+label: Quick-Opening Device

+type: select

+options:

+ - "None"

+ - "Accelerator"

+ - "Exhauster"

+```

+### An accelerator senses the rate of pressure drop when a sprinkler opens and vents the intermediate chamber of the dry-pipe valve, so the clapper releases before the system pressure has fallen to the trip point on its own. An exhauster instead vents the system gas to atmosphere through a large port ahead of the water, shortening the time to expel the gas rather than the time to trip. Accelerators are the device manufacturers now list with their valves; exhausters remain in service on existing systems and are procurable for some valve models. {note}

+### Where the calculated delivery time without a quick-opening device exceeds the datasheet limit, a quick-opening device shall be provided or the system shall be subdivided until the limit is met.

+### Where an accelerator is furnished, it shall include the anti-flood provision the listing requires, so that water entering the system after the trip cannot reach the accelerator internals.

+### A quick-opening device shortens the delivery time but does not remove the delay, and the design area increase NFPA 13 applies to a dry system is not reduced because a device is installed. {note}

+# Dry-Pipe Valve and Trim {toc}

+## Dry-Pipe Valve {toc}

+### The dry-pipe valve type shall be as indicated in the datasheet.

+```datasheet

+label: Dry-Pipe Valve Type

+type: radio

+options:

+ - "Differential dry-pipe valve"

+ - "Low-differential dry-pipe valve"

+```

+### A differential valve holds its clapper closed with a large air-side area against a small water-side area, so a supervisory pressure of a fraction of the water pressure keeps it seated; a low-differential valve holds with a mechanical latch or a smaller area ratio and is held at a supervisory pressure closer to the water pressure. The differential valve needs less gas and a smaller supply; the low-differential valve trips from a smaller pressure loss and pairs with a nitrogen supply that is already sized to hold the higher pressure. {note}

+### The dry-pipe valve size shall be as indicated in the datasheet.

+```datasheet

+label: Dry-Pipe Valve Size

+type: range

+unit: in.

+drawing_ref: "the fire protection riser diagram"

+min: 2

+max: 8

+setpoints: [2, 2.5, 3, 4, 6, 8]

+default: deferred

+```

+### The dry-pipe valve body material shall be as indicated in the datasheet.

+```datasheet

+label: Dry-Pipe Valve Body Material

+type: select

+options:

+ - "Cast iron"

+ - "Ductile iron"

+default: manufacturer

+```

+### The dry-pipe valve shall be installed with the manufacturer's listed trim, and the trim shall not be assembled in the field from components that are not part of the listing.

+### Where the valve listing calls for priming water, the trim shall include the priming water connection, the priming level test valve, and a means to confirm the priming level without opening the valve.

+### The trim shall include a water-side pressure gauge and a gas-side pressure gauge, each readable from the floor of the valve enclosure.

+### The trim shall include a drain for the intermediate chamber, arranged so that the chamber can be confirmed dry before the valve is reset.

+### An intermediate chamber that is not drained before reset holds the valve off its seat, and the valve either fails to reset or trips the moment the supply is reopened. The drain and its sight connection are what let the technician confirm the chamber state instead of guessing at it. {note}

+### The main drain shall discharge where a full-flow trip test can be run without damage to the building.

+### The fire department connection shall enter the system on the system side of the dry-pipe valve clapper, and the connection, its check valve, and the automatic drain between the check valve and the dry-pipe valve shall be as required by [[sync/fire-department-connections]].

+### The fire department connection sign shall identify the connection as serving a dry-pipe system.

+## Valve Enclosure {toc}

+### The dry-pipe valve, its trim, its supply piping, and the supervisory gas source shall be located in an enclosure that is maintained at not less than the temperature indicated in the datasheet.

+```datasheet

+label: Valve Enclosure Minimum Temperature

+type: range

+unit: °F

+min: 40

+max: 60

+setpoints: [40, 45, 50, 55, 60]

+default: 40

+```

+### The means of heating the valve enclosure shall be as indicated in the datasheet.

+```datasheet

+label: Valve Enclosure Heating

+type: select

+options:

+ - "Heated room of the building"

+ - "Dedicated electric unit heater in the valve enclosure"

+ - "Hydronic or steam unit heater in the valve enclosure"

+ - "Listed insulated and heated valve enclosure"

+```

+### The water side of the dry-pipe valve is full, and the trim carries priming water and drain water, so the valve is a wet component that has to live in heated space even though everything downstream of it is dry. A valve enclosure that shares the building's heating is only as reliable as that heating; a dedicated heater is only as reliable as its circuit; a listed heated enclosure trades both for a cabinet with its own thermostat and its own supervision. {note}

+### The valve enclosure shall provide clearance to operate every trim valve, read every gauge, service the supervisory gas source, and remove the valve cover for internal inspection.

+### The valve enclosure shall be provided with a floor drain or an exterior discharge sized for the main drain flow.

+# Supervisory Gas Supply {toc}

+## Supervisory Gas Source {toc}

+### The supervisory gas source for each dry-pipe system shall be as indicated in the datasheet.

+```datasheet

+label: Supervisory Gas Source

+type: select

+options:

+ - "Dedicated riser-mounted air compressor"

+ - "Dedicated tank-mounted air compressor"

+ - "Plant compressed air system through an air maintenance device"

+ - "Membrane nitrogen generator"

+ - "Pressure-swing adsorption nitrogen generator"

+ - "Nitrogen cylinders through a pressure regulator"

+```

+### The supervisory gas is either air or nitrogen, and the source selected fixes which. Air is the gas a compressor supplies and the gas that oxidizes the pipe interior; nitrogen displaces the oxygen and is supplied by a generator that separates it from compressed air on site or by cylinders that are exchanged. {note}

+### A dedicated compressor runs only when the dry system needs gas, draws from the heated enclosure, and stops when its own pressure switch is satisfied. A plant air system supplies gas at plant pressure, carries whatever oil and moisture the plant's own conditioning leaves in it, and is unavailable whenever the plant compressor is down for maintenance or the plant is shut down. Where the plant air is dried and filtered to the condition the sprinkler system needs and is kept in service through building shutdowns, it removes a compressor from the valve room; where it is not, the dry system inherits the plant's oil, water, and outages. {note}

+### A membrane generator separates nitrogen continuously with no moving parts beyond its feed compressor and suits a system that leaks slowly and needs a steady trickle; a pressure-swing adsorption generator produces higher purity from a smaller feed and cycles between beds. Cylinders supply no purity risk and no electrical load, and run out, so they suit a small system, a temporary installation, or a site where a purity-supervised cylinder bank is exchanged on a schedule. {note}

+### Where the supervisory gas source is a plant compressed air system, the connection to the dry-pipe system shall pass through a listed air maintenance device and a check valve, and the plant air shall be dried and filtered to the condition required under this standard before it enters the device.

+### Where the supervisory gas source serves more than one dry-pipe system, each system shall be connected through its own listed air maintenance device and check valve, so that a trip on one system does not depressurize the others.

+### An air maintenance device restricts the rate at which gas enters the system, so that a leak large enough to trip the valve is not masked by a supply large enough to keep up with it. A supply piped directly to the system without the restriction turns every leak into a pressure the valve never sees. {note}

+### The supervisory gas supply shall be provided with a listed relief valve, set not higher than the pressure rating of the system components, in accordance with NFPA 13.

+### The compressor or nitrogen generator shall be supplied from a dedicated branch circuit identified at the panelboard as serving the fire sprinkler supervisory gas supply, and the circuit shall comply with NFPA 70.

+### Where the supervisory gas source is a nitrogen generator, the generator shall be listed for the purpose, and the feed compressor, filtration, and separation module shall be furnished as the listed assembly.

+## Supervisory Gas Pressure {toc}

+### The normal supervisory gas pressure of each dry-pipe system shall be as indicated in the datasheet.

+```datasheet

+label: Supervisory Gas Pressure

+type: range

+unit: psi

+derived: "the trip pressure of the selected dry-pipe valve at [[parameter: site-water-supply-pressure-maximum]], or at the fire pump churn pressure where a pump serves the system, plus the margin of 20 psi or the valve manufacturer's published margin, whichever governs under NFPA 13"

+min: 10

+max: 80

+setpoints: [10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80]

+default: derived

+```

+### The supervisory pressure is bounded on both sides. Below the trip pressure plus its margin, a supply pressure surge or a fire pump start trips the valve with no fire; above what the margin requires, the surplus gas lengthens the delivery time by the volume it occupies at that pressure, and every psi of surplus is a psi the leak has to bleed before the valve responds to an open sprinkler. {note}

+### The supervisory pressure shall not be raised above the datasheet value to compensate for leakage.

+### The low-pressure supervisory switch setpoint of each dry-pipe system shall be as indicated in the datasheet.

+```datasheet

+label: Low-Pressure Supervisory Setpoint

+type: range

+unit: psi

+derived: "the supervisory gas pressure and the trip pressure of the selected dry-pipe valve, set between them at the margin above the trip pressure the valve manufacturer publishes"

+min: 5

+max: 70

+setpoints: [5, 10, 15, 20, 25, 30, 35, 40, 50, 60, 70]

+default: derived

+```

+### Each dry-pipe system shall be provided with a listed low-pressure supervisory switch that transmits a supervisory signal to the fire alarm system when the supervisory gas pressure falls to the setpoint, in accordance with NFPA 72 and [[sync/fire-alarm-systems]].

+### The additional supervisory signals provided for each dry-pipe system shall be as indicated in the datasheet.

+```datasheet

+label: Additional Supervisory Signals

+type: checkbox

+options:

+ - "High supervisory gas pressure"

+ - "Valve enclosure low temperature"

+ - "Air compressor fault or excessive run time"

+ - "Nitrogen generator trouble or low purity"

+```

+### A high-pressure signal reports a failed regulator or a stuck air maintenance device, which raises the delivery time without any other symptom. A run-time signal reports a leak by the compressor working to keep up with it, which is the earliest sign a system gives. {note}

+## Air Supply Capacity and Conditioning {toc}

+### Requirements in this article apply where the supervisory gas is supplied by an air compressor or by the feed compressor of a nitrogen generator.

+### The air supply shall restore a dry-pipe system from atmospheric pressure to its normal supervisory pressure within the time indicated in the datasheet.

+```datasheet

+label: Air Supply Restoration Time

+type: range

+unit: minutes

+min: 10

+max: 30

+setpoints: [10, 15, 20, 30]

+default: 30

+```

+### NFPA 13 requires the automatic supply to restore normal pressure within 30 minutes. A shorter time returns the system to service sooner after a trip test or a trip, at the cost of a larger compressor and, through the air maintenance device, no faster fill on a system that has a leak. {note}

+### The capacity of the air supply shall be as indicated in the datasheet.

+```datasheet

+label: Air Supply Capacity

+type: range

+unit: cfm

+derived: "the calculated system volume, the supervisory gas pressure, and the restoration time indicated in the datasheet, applied to the compressor sizing method of NFPA 13 or the manufacturer's published sizing"

+min: 0.5

+max: 30

+setpoints: [0.5, 1, 1.5, 2, 3, 4, 5, 7.5, 10, 15, 20, 30]

+default: derived

+```

+### The compressor shall draw its intake from the heated valve enclosure or from another heated interior space, unless the supervisory gas drying indicated in the datasheet is provided downstream of the compressor.

+### The moisture a compressor takes in leaves the receiver as vapor and condenses in the first cold pipe it reaches. Air drawn from a heated room carries less water per cubic foot than air drawn from a humid summer exterior, and it carries none of the winter condensation that an intake in the cold space itself produces. {note}

+### The supervisory gas drying provided shall be as indicated in the datasheet.

+```datasheet

+label: Supervisory Gas Drying

+type: select

+derived: "the pressure dew point needed to keep condensate from forming in the coldest space the dry piping serves"

+options:

+ - "None"

+ - "Refrigerated air dryer"

+ - "Desiccant air dryer"

+ - "Membrane air dryer"

+default: derived

+```

+### Where any part of the dry piping serves a space held at or below 32°F, the supervisory gas shall be dried to a pressure dew point below the lowest temperature of that space.

+### Where the supervisory gas source is a plant compressed air system, the drying and filtration of the plant air shall be confirmed against the datasheet value, and additional drying shall be provided at the connection where the plant air does not meet it.

+### The air supply shall be provided with a coalescing filter that removes compressor oil before the gas enters the system.

+## Nitrogen Supply {toc}

+### Requirements in this article apply where the supervisory gas is nitrogen.

+### The nitrogen purity maintained in the system shall be not less than the value indicated in the datasheet, measured at the remote end of the system.

+```datasheet

+label: Nitrogen Purity at the System

+type: range

+unit: '%'

+min: 95

+max: 99

+setpoints: [95, 98, 99]

+default: 98

+```

+### The corrosion credit NFPA 13 and FM Global Data Sheet 2-1 give a nitrogen-supervised system rests on the oxygen concentration being held low enough that the pipe interior does not corrode at a rate that matters, and 98 percent nitrogen is the purity those documents describe. A higher purity costs generator capacity and purge time and buys a smaller further reduction in oxygen. {note}

+### The purge provision by which the initial air charge is displaced shall be as indicated in the datasheet.

+```datasheet

+label: Nitrogen Purge Provision

+type: select

+options:

+ - "Listed automatic purge vent at the remote end of each system"

+ - "Manual purge valve at the remote end of each system"

+ - "Purge through the inspector's test connection"

+```

+### A system filled with nitrogen from a generator still holds the air it was tested with, and the nitrogen reaches the datasheet purity only as that air is vented at the far end while the generator makes up the loss. An automatic vent runs the purge unattended over the days it takes and closes on purity or on a trip; a manual valve does the same work on someone's schedule; the test connection does it only while a technician stands at it. {note}

+### The system shall be purged after the air leakage test and after every subsequent trip or drain-down until the purity at the remote end reaches the datasheet value, and the purity shall be recorded.

+### Where nitrogen is the supervisory gas, the low-pressure supervisory switch, the relief valve, the air maintenance device, and the gauges shall be as required for air under this standard.

+# Interior Corrosion Mitigation {toc}

+## A dry system corrodes from the inside faster than a wet system because its interior is wetted and dried repeatedly, with water left standing at every low point and oxygen supplied continuously by the gas above it. The wet-and-dry line at each puddle is where oxygen pitting concentrates, and the same standing water is where microbiologically influenced corrosion establishes. {note}

+## The interior corrosion protection of the dry piping shall be as indicated in the datasheet.

+```datasheet

+label: Dry Piping Interior Corrosion Protection

+type: select

+options:

+ - "Black steel, uncoated interior"

+ - "Galvanized steel"

+ - "Internally coated steel"

+ - "Stainless steel"

+```

+## Galvanizing protects the interior by sacrificial zinc, which holds until the zinc is consumed and then leaves bare steel; where the zinc is damaged at threads or where water stands, the exposed steel pits faster than it would in an ungalvanized pipe, because the surrounding zinc drives the attack to the bare spot. Black steel supervised with nitrogen has no oxygen to feed general corrosion or pitting and is the combination FM Global Data Sheet 2-1 describes for a new dry system. Black steel supervised with air corrodes at the rate the standing water and the oxygen supply allow, which is the condition that produced the service history the other options answer. An internal coating or stainless steel removes the steel from contact with the water at a material cost that a large system or a corrosive supply may justify. {note}

+## The pipe finish and material selected for the dry piping under [[sync/fire-protection-piping]] shall be consistent with the interior corrosion protection indicated in the datasheet.

+## Where galvanized pipe is selected, fittings and couplings on the dry piping shall be galvanized, and field-cut threads and welds shall be restored with a cold-galvanizing compound before the joint is made up.

+## A black fitting on a galvanized pipe puts bare steel at the threaded joint, which is the location where water stands last and drains least, so the one unprotected component sits at the one place the protection was most needed. {note}

+## Pipe used on the dry piping shall carry a listing for dry-pipe service where the pipe is of a wall thickness lighter than Schedule 40 or is of a nonmetallic material.

+## Pipe listed for wet service only is listed on the assumption that its interior stays wet and its exterior stays warm. Light-wall steel corrodes through sooner in a wet-and-dry interior, and a nonmetallic pipe that is not listed for dry service has not been tested for the drying, the cold, or the pressure surge of a trip. {note}

+# Pitch and Drainage {toc}

+## Pitch {toc}

+### Dry piping shall be pitched to drain to the dry-pipe valve or to an auxiliary drain, with branch lines pitched not less than the value indicated in the datasheet.

+```datasheet

+label: Minimum Branch Line Pitch

+type: range

+unit: in. per 10 ft

+min: 0.5

+max: 2

+setpoints: [0.5, 1, 1.5, 2]

+default: 0.5

+```

+### Mains shall be pitched not less than the value indicated in the datasheet.

+```datasheet

+label: Minimum Main Pitch

+type: range

+unit: in. per 10 ft

+min: 0.25

+max: 1

+setpoints: [0.25, 0.5, 0.75, 1]

+default: 0.25

+```

+### The datasheet defaults are the NFPA 13 minimums for a dry system. A steeper pitch drains faster and leaves less water behind after a trip, at the cost of headroom lost across a long run and more hanger elevations to set. {note}

+### Mains serving a space held at or below 32°F shall be pitched not less than 1/2 in. per 10 ft regardless of the datasheet value.

+### The pitch of every main and branch line shall be verified with a level as the piping is hung and before the ceiling below it is closed.

+### Pipe that reads level on the plan and sags between hangers holds water in each sag, and the sag is invisible once the ceiling is up. Verifying pitch at every section while it is still open is the only time the correction is inexpensive. {note}

+## Auxiliary Drains {toc}

+### An auxiliary drain shall be provided at every section of dry piping that cannot drain to the dry-pipe valve by gravity.

+### The locations of auxiliary drains shall be as indicated on [[drawing: the pitch and drainage plan]].

+### The auxiliary drain for a trapped section holding more than 5 gal shall be as indicated in the datasheet.

+```datasheet

+label: Auxiliary Drain for Trapped Sections Over 5 gal

+type: radio

+options:

+ - "Two-valve drum drip"

+ - "Listed automatic auxiliary drain"

+default: "Two-valve drum drip"

+```

+### A drum drip holds the water that collects in its condensate nipple between an upper valve and a lower valve, and is emptied by closing the upper valve, opening the lower, closing the lower, and reopening the upper, so that the system is never open to atmosphere. An automatic drain does the same on a float without an operator, and adds a device with its own listing, its own leak path, and its own maintenance. {note}

+### A two-valve drum drip shall consist of two 1 in. valves and a 2 in. by 12 in. condensate nipple, or the equivalent arrangement NFPA 13 permits.

+### The auxiliary drain for a trapped section holding not more than 5 gal shall be a valve of not less than 1/2 in. with a plug or a nipple and cap, in accordance with NFPA 13.

+### Auxiliary drains shall be located so that they can be operated from the floor or from a portable ladder without removal of permanent construction, and access panels shall be provided at auxiliary drains above finished ceilings.

+### Each auxiliary drain shall be identified with a permanent sign stating that it is a sprinkler auxiliary drain and the section it drains, and the sign at the dry-pipe valve shall list the number and locations of every auxiliary drain on the system.

+### Auxiliary drains located in unheated space hold water in the condensate nipple and freeze if they are not drained, so the drain that protects the piping is itself the component that most needs the seasonal drain-down NFPA 25 requires. {note}

+## Inspector's Test Connection {toc}

+### Each dry-pipe system shall be provided with an inspector's test connection at the most remote point of the system, with a valve and an orifice equal to the smallest sprinkler orifice on the system, in accordance with NFPA 13.

+### The test connection shall discharge where the flow can be observed and where water discharged in freezing weather will not damage the building or create a hazard.

+### The test connection valve on a dry system shall be arranged so that the piping between the valve and the discharge drains after the test and does not hold water in unheated space.

+# Refrigerated Space Provisions {toc}

+## Requirements in this article apply where dry piping serves a space held at or below 32°F.

+## A freezer is the dry system's hardest service. The gas condenses on contact with the pipe wall, the condensate freezes where it lands, ice grows inward from the wall at the point the pipe enters the cold space, and a trip fills the piping with water that has minutes before it becomes ice. {note}

+## The dry piping shall enter the refrigerated space from above and shall be arranged so that water drains out of the space and back toward the dry-pipe valve.

+## An inspection point shall be provided in the supply pipe at its entry into the refrigerated space, arranged as a removable flanged or grooved spool or as a listed ice-plug detection provision, so that the interior can be examined for an ice plug without cutting the pipe.

+## The ice plug forms where the warm supply pipe meets the cold air, and it closes the pipe from the wall inward with no change in supervisory pressure and no signal to any device. The only way to find it is to look. {note}

+## The penetration of the insulated envelope by the dry piping shall be sealed against vapor migration into the insulation, and the seal shall be compatible with the envelope insulation and the pipe finish.

+## After a trip or a test in a refrigerated space, the piping shall be drained and dried, and the space shall be returned to service only after the auxiliary drains and the piping interior have been confirmed free of ice.

+# Sprinklers on Dry Piping {toc}

+## Sprinklers on dry piping shall be upright sprinklers, listed dry pendent sprinklers, listed dry sidewall sprinklers, or listed horizontal sidewall sprinklers, except that a pendent sprinkler may be installed where both the sprinkler and the branch line serving it are in heated space, in accordance with NFPA 13.

+## A standard pendent sprinkler on dry piping hangs below the branch line with its inlet at the low point, so the water left after a trip collects in the sprinkler body and freezes there. An upright sprinkler drains back into the branch line, and a dry pendent carries its seal up at the branch line with an empty barrel below it. {note}

+## The sprinkler type, orifice, temperature rating, and finish for each area shall be as selected under [[sync/wet-pipe-fire-sprinkler-systems]].

+## The barrel length of each dry pendent and dry sidewall sprinkler shall be as indicated on [[drawing: the sprinkler schedule]].

+## The barrel length of a dry sprinkler shall place its inlet seal in heated space, in accordance with the sprinkler listing and the insulated boundary through which the barrel passes.

+# Waterflow Alarm {toc}

+## The waterflow alarm for each dry-pipe system shall be initiated by a listed alarm pressure switch connected to the alarm outlet of the dry-pipe valve, and the switch shall transmit a waterflow signal to the fire alarm system in accordance with NFPA 72 and [[sync/fire-alarm-systems]].

+## Vane-type waterflow switches shall not be installed in dry piping.

+## The pressure switch on the alarm outlet sees full supply pressure the moment the clapper opens, so the alarm on a dry system is transmitted before water has reached the sprinkler rather than after. A vane in dry piping is struck by the slug of gas and water that a trip drives through the pipe, which NFPA 13 prohibits because the vane and the alarm both fail under it. {note}

+## Where a water motor alarm is selected under the alarm policy of [[sync/wet-pipe-fire-sprinkler-systems]], the alarm line from the dry-pipe valve to the gong shall be arranged to drain and shall not hold water in unheated space.

+# Installation {toc}

+## Piping shall be installed to the pitch, drainage, and auxiliary drain arrangement of the reviewed pitch and drainage plan, and a deviation that creates a trapped section shall be reported to the Engineer of Record before the section is hung.

+## Open ends of dry piping shall be capped whenever work stops, and the piping shall be kept free of cutting debris, thread chips, and construction material until it is closed.

+## The trim of a dry-pipe valve, the quick-opening device, and the air maintenance device pass gas and water through small orifices that a chip of pipe scale can close, and the first trip after construction is when the debris that entered during construction arrives at those orifices. {note}

+## After the hydrostatic test required under [[sync/wet-pipe-fire-sprinkler-systems]], the dry piping shall be drained at the main drain and at every auxiliary drain before the system is placed under supervisory gas, and each auxiliary drain shall be operated and confirmed clear as part of that drain-down.

+## The dry-pipe valve shall be installed with its trim oriented as the listing requires and with the gauges, the priming connection, and the intermediate chamber drain reachable from the floor of the valve enclosure.

+## A sign shall be provided at the dry-pipe valve stating the calculated system volume, the normal supervisory gas pressure, the low-pressure supervisory setpoint, the supervisory gas, the calculated and the tested water delivery time, and the number and locations of the auxiliary drains, in addition to the signs required by [[sync/wet-pipe-fire-sprinkler-systems]].

+# Testing {toc}

+## Cold-Weather Testing Sequence {toc}

+### Whether an interim air test may substitute for the hydrostatic test while freezing weather prevents it shall be as indicated in the datasheet.

+```datasheet

+label: Interim Cold-Weather Air Test

+type: radio

+options:

+ - "Permitted, with the hydrostatic test completed before acceptance"

+ - "Not permitted"

+```

+### NFPA 13 permits an interim air test at 40 psi for 24 hours where freezing weather prevents a hydrostatic test, with the hydrostatic test to follow when the weather permits. Accepting the interim test keeps the construction schedule through the winter; refusing it keeps the sequence simple at the cost of holding the system until it can be filled. {note}

+### Where the interim test is permitted, the hydrostatic test required under [[sync/wet-pipe-fire-sprinkler-systems]] shall be completed before the system is accepted, and the acceptance shall not be conditioned on the interim result alone.

+## Air Leakage Test {toc}

+### In addition to the hydrostatic test, each dry-pipe system shall be tested with air or nitrogen at 40 psi for 24 hours, and the pressure loss over the 24 hours shall not exceed 1.5 psi, in accordance with NFPA 13.

+### The pressure and the ambient temperature at the piping shall be recorded at the start and at the end of the 24 hours, and a pressure change consistent with the temperature change shall not be counted as leakage.

+### A dry system leaks air through joints that held water. Water does not pass a thread imperfection that air passes freely, and the hydrostatic test proves the joint against the wrong fluid. The 24-hour air test is the one that finds the joints the compressor would otherwise have spent its life keeping up with. {note}

+### Leaks shall be located with a leak-detection solution or an ultrasonic detector, and the joint shall be remade rather than sealed from the outside.

+### A system that fails the air leakage test shall be retested in full after the repair, and the cost of the repair and of every retest shall be borne by the Contractor.

+## Trip Test {toc}

+### Each dry-pipe valve shall be trip tested at acceptance by opening the inspector's test valve fully with the control valve fully open, the system at its normal supervisory pressure, and the quick-opening device in service where one is furnished, in accordance with NFPA 13.

+### The supervisory pressure at the start, the pressure at which the valve tripped, the time to the trip, and the time from the opening of the test valve to water at the test connection shall be recorded.

+### Where the system is subject to a water delivery time requirement, the time to water at the test connection shall not exceed the datasheet limit.

+### Where the tested delivery time exceeds the limit, the Contractor shall correct the cause and repeat the test, and the cost of the correction and the retest shall be borne by the Contractor.

+### A tested delivery time longer than the calculated one usually points to one of a few causes: a supervisory pressure set higher than the calculation assumed, an orifice in the trim or the accelerator partly closed by debris, trapped sections holding gas the calculation assumed was pipe, or an air supply that could not be isolated during the test. {note}

+### The trip test shall be witnessed by the Authority Having Jurisdiction where the Authority requires it, and the Contractor shall schedule the test with the Authority not less than five working days before it is run.

+### After the trip test the system shall be drained at the main drain and at every auxiliary drain, the intermediate chamber shall be drained and confirmed dry, the valve shall be reset in accordance with the manufacturer's instructions, and the system shall be restored to its normal supervisory pressure and, where nitrogen is the supervisory gas, purged to the datasheet purity.

+## Alarm and Supervisory Device Tests {toc}

+### The alarm pressure switch shall be tested during the trip test by confirming that the fire alarm system received the waterflow signal, and the time from the trip to the signal shall be recorded.

+### The low-pressure supervisory switch shall be tested by bleeding gas from the system at the inspector's test connection until the switch operates, and the pressure at which it operated shall be recorded and compared with the datasheet setpoint.

+### Each additional supervisory signal indicated in the datasheet shall be tested by producing its condition, and the receipt of each signal at the fire alarm system shall be recorded.

+### The air supply shall be tested by depressurizing the system to atmosphere and timing the restoration to normal supervisory pressure, and the time shall not exceed the datasheet restoration time.

+# Spare Parts {toc}

+## The Contractor shall deliver the spare parts indicated in the datasheet to the Owner before the system is accepted, and shall obtain a signed receipt for them.

+```datasheet

+label: Dry-Pipe Spare Parts to Be Furnished

+type: checkbox

+options:

+ - "Dry-pipe valve clapper facing and seat seal kit"

+ - "Quick-opening device service kit"

+ - "Air compressor intake filter element"

+ - "Nitrogen generator filter elements for one service interval"

+ - "One two-valve drum drip assembly"

+```

+## Spare parts shall be the same make and model as the installed items, delivered in their original packaging, and labeled with the system they serve.

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