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Hydronic Piping

Rev8
IssuedAug 26, 2026
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1 Scope

NOTE This standard covers the pipe, fittings, joints, and installation of closed-loop hydronic distribution piping carrying heating hot water, chilled water, dual-temperature water, and condenser water between central plant equipment and the terminal equipment that conditions occupied spaces. (1.1)
NOTE The boundary of the work is the pipe itself and the joints that make it continuous: material and wall selection, joining method, fittings and flanges, dissimilar-metal isolation, routing and support interfaces, and the structural pressure test that proves the assembly before it is concealed. (1.2)
NOTE Hydronic piping is the one part of an HVAC system that is installed once, buried in ceilings and shafts, and expected to hold pressure for the life of the building without inspection. A joint that leaks after the ceiling closes costs many times what it cost to make, and the water it releases damages work by other trades. That asymmetry is why this standard is prescriptive about qualification, examination, and testing, and permissive about the choices a designer legitimately owns. (1.3)
NOTE The systems in scope operate within the ASME B31.9 building-services envelope. Above 250°F or above 160 psig the design falls under ASME B31.1 and this standard does not apply. (1.4)
1.5 Piping and joining shall comply with ASME B31.9, the adopted edition of the International Mechanical Code Chapter 12, and the requirements of the Authority Having Jurisdiction.
1.6 Where a hydronic system carries a glycol solution, every requirement of this standard for water service applies equally to the glycol solution, and the additional gasket, seal, and venting provisions of this standard apply.
NOTE The following are outside this scope and are governed by the companion standards named. (1.7)
  • General-duty isolation, shutoff, and throttling valves - HVAC Piping ValvesGeneral-Duty Valves for HVAC PipingResolves to the current adopted revision.sync/hvac-piping-valves.
  • Balancing valves, pressure-independent control valves, strainers, flexible connectors, gauges, and thermometers - Hydronic SpecialtiesHydronic SpecialtiesResolves to the current adopted revision.sync/hydronic-specialties.
  • Expansion tanks, air separators, dirt separators, and automatic air vents - Expansion Tanks And Air SeparatorsExpansion Tanks and Air SeparatorsResolves to the current adopted revision.sync/expansion-tanks-and-air-separators.
  • Expansion joints, fabricated expansion loops, and the anchors and guides that make them work - Expansion Fittings And LoopsExpansion Fittings and Loops for PipingResolves to the current adopted revision.sync/expansion-fittings-and-loops.
  • Hangers, supports, structural attachments, and seismic bracing - Hangers And SupportsHangers and Supports for Mechanical Piping and EquipmentResolves to the current adopted revision.sync/hangers-and-supports.
  • Field-applied pipe insulation, jacketing, and vapor retarders - Mechanical InsulationMechanical InsulationResolves to the current adopted revision.sync/mechanical-insulation.
  • Pipe markers, valve tags, and equipment identification - Mechanical IdentificationMechanical IdentificationResolves to the current adopted revision.sync/mechanical-identification.
  • Cleaning, flushing, passivation, and the inhibitor start charge - Hydronic Cleaning And FlushingHydronic System Cleaning and FlushingResolves to the current adopted revision.sync/hydronic-cleaning-and-flushing and HVAC Water TreatmentHVAC Water TreatmentResolves to the current adopted revision.sync/hvac-water-treatment.
  • Pumps, pump sets, and pump motor drives - HVAC PumpsHVAC PumpsResolves to the current adopted revision.sync/hvac-pumps and HVAC Variable Frequency DrivesHVAC Variable Frequency DrivesResolves to the current adopted revision.sync/hvac-variable-frequency-drives.
  • Central-plant, large-diameter chilled and condenser water distribution - Chilled And Condenser Water PipingChilled and Condenser Water PipingResolves to the current adopted revision.sync/chilled-and-condenser-water-piping.
  • Air and water balancing of the completed systems - Testing Adjusting And BalancingTesting, Adjusting, and Balancing for HVACResolves to the current adopted revision.sync/testing-adjusting-and-balancing.

2 Referenced Standards

2.1 Materials, fabrication, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
2.2 Where the contract documents, the adopted building code, or a referenced standard conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
Standard Title
ANSI/ASHRAE/IES 90.1 Energy Standard for Buildings Except Low-Rise Residential Buildings
ASME A13.1 Scheme for the Identification of Piping Systems
ASME B1.20.1 Pipe Threads, General Purpose (Inch)
ASME B16.3 Malleable Iron Threaded Fittings, Classes 150 and 300
ASME B16.5 Pipe Flanges and Flanged Fittings, NPS 1/2 through NPS 24
ASME B16.9 Factory-Made Wrought Buttwelding Fittings
ASME B16.11 Forged Fittings, Socket-Welding and Threaded
ASME B16.18 Cast Copper Alloy Solder Joint Pressure Fittings
ASME B16.21 Nonmetallic Flat Gaskets for Pipe Flanges
ASME B16.22 Wrought Copper and Copper Alloy Solder Joint Pressure Fittings
ASME B16.24 Cast Copper Alloy Pipe Flanges, Flanged Fittings, and Valves
ASME B16.25 Buttwelding Ends
ASME B16.50 Wrought Copper and Copper Alloy Braze-Joint Pressure Fittings
ASME B31.9 Building Services Piping
ASME B36.10M Welded and Seamless Wrought Steel Pipe
ASME BPVC Section IX Boiler and Pressure Vessel Code — Welding, Brazing, and Fusing Qualifications
ASTM A53 / A53M Pipe, Steel, Black and Hot-Dipped, Zinc-Coated, Welded and Seamless
ASTM A105 / A105M Carbon Steel Forgings for Piping Applications
ASTM A106 / A106M Seamless Carbon Steel Pipe for High-Temperature Service
ASTM A234 / A234M Piping Fittings of Wrought Carbon Steel and Alloy Steel for Moderate and High Temperature Service
ASTM A312 / A312M Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes
ASTM A536 Ductile Iron Castings
ASTM B32 Solder Metal
ASTM B88 Seamless Copper Water Tube
ASTM B813 Liquid and Paste Fluxes for Soldering of Copper and Copper Alloy Tube and Fittings
ASTM B828 Making Capillary Joints by Soldering of Copper and Copper Alloy Tube and Fittings
ASTM F441 / F441M Chlorinated Poly(Vinyl Chloride) (CPVC) Plastic Pipe, Schedules 40 and 80
ASTM F876 Crosslinked Polyethylene (PEX) Tubing
ASTM F2389 Pressure-Rated Polypropylene (PP) Piping Systems
AWS A5.8 / A5.8M Filler Metals for Brazing and Braze Welding
AWWA C606 Grooved and Shouldered Joints
IMC International Mechanical Code, Chapter 12 (Hydronic Piping)
MSS SP-25 Standard Marking System for Valves, Fittings, Flanges, and Unions
MSS SP-58 Pipe Hangers and Supports — Materials, Design, Manufacture, Selection, Application, and Installation

3 Submittals

3.1 Action Submittals

3.1.1 The Contractor shall submit the following for the Engineer of Record's review and return before any hydronic pipe, fitting, or joining component is procured:
  • Pipe product data for each service and size band, identifying the material standard, grade, wall schedule or tube type, marking, pressure rating, and service temperature limit
  • Fitting product data for each joining method, identifying the governing ASME or ASTM standard, material, and pressure class, with the compatible pipe wall schedule stated
  • Flange, bolting, and gasket product data, identifying the pressure class, facing, gasket material, and temperature limit
  • Grooved coupling system product data covering couplings, fittings, gaskets, and the grooving method, with the gasket compound and its service temperature range stated for each service
  • Press-connect system product data, including the listing, the sealing element compound, the jaw and tool set required, and the size range covered by the listing
  • Polymer piping system product data, including the pipe standard, the listed joining system, the oxygen diffusion barrier where required, and the pressure-temperature derating curve
  • Dissimilar-metal isolation fitting product data for each size band, showing the pressure and temperature rating and the construction of the insulating barrier
  • Welding and brazing procedure specifications and supporting procedure qualification records under ASME BPVC Section IX for every joint configuration to be used
  • Qualification records for each welder, welding operator, and brazer who will perform work on this project, with the qualification date and continuity record
  • A pressure test plan identifying test boundaries, staging, medium, pressure, hold duration, isolation method, gauge selection, and the sequence that allows concealed work to be tested before it is covered
  • Piping coordination drawings at a scale sufficient to resolve conflicts, showing routing, sizes, joint types, support and anchor points, and equipment connection details
Action Submittals Requiredcheckbox
☑ Pipe product data by service and size band
☑ Fitting product data by joining method
☑ Flange, bolting, and gasket product data
☐ Grooved coupling system product data
☐ Press-connect system product data
☐ Polymer piping system product data
☐ Dissimilar-metal isolation fitting product data
☑ Welding and brazing procedure specifications and qualification records
☑ Welder, operator, and brazer qualification records
☑ Pressure test plan
☑ Piping coordination drawings
3.1.2 Work on a system shall not proceed until the submittals covering that system have been returned by the Engineer of Record.
3.1.3 Each submittal shall be internally consistent across pipe, fittings, joints, and flanges before it is transmitted, and the Contractor shall bear the cost of resubmission caused by internal inconsistency in its own submittal.

3.2 Closeout Submittals

3.2.1 The Contractor shall submit the following at substantial completion, before the hydronic piping work is accepted:
  • Signed and dated pressure test reports for every test boundary, recording the medium, pressure, hold duration, observed pressure loss, and the pass determination
  • A weld and braze record listing each joint by location or joint number, the welder or brazer identification, the procedure used, and the examination result
  • Nondestructive examination reports for every joint examined beyond visual, with the examiner's certification level
  • As-built piping drawings recording the installed routing, sizes, joint types, anchor and guide locations, and the locations of concealed joints
  • A concealed-joint schedule identifying every joint that is not accessible after completion, with its access route
  • Material certifications and mill test reports for pipe and fittings where required by the accepted action submittals
Closeout Submittals Requiredcheckbox
☑ Signed pressure test reports for every test boundary
☑ Weld and braze record
☐ Nondestructive examination reports
☑ As-built piping drawings
☑ Concealed-joint schedule
☐ Material certifications and mill test reports

4 Quality Assurance

4.1 Installer and Welder Qualification

4.1.1 The mechanical contractor performing hydronic piping work shall have completed at least three commercial or institutional hydronic piping installations comparable to this project in scope and complexity within the preceding five years, and shall submit those project references on request.
4.1.2 Where the parties disagree whether a submitted reference project is comparable in scope and complexity, the Engineer of Record shall make the initial determination.
4.1.3 Personnel making welded or brazed joints shall hold current qualification under ASME BPVC Section IX for the process, position, material, and wall thickness of the joint being made.
4.1.4 Qualification and continuity records for every welder, welding operator, and brazer on site shall be available at the site for inspection throughout installation.
4.1.5 A welder or brazer whose Section IX continuity record has lapsed shall requalify before making any production joint on this project.
4.1.6 Joints made by personnel who were not qualified at the time the joint was made shall be cut out and remade, and the Contractor shall bear the cost of the removal, the replacement material, the remake, the re-examination, and the repair of any other trade's work disturbed by that removal.
4.1.7 Personnel making press-connect joints shall have completed the pipe system manufacturer's training for the tool set and size range in use.
4.1.8 The Contractor shall keep a current copy of ASME B31.9 at the site throughout installation.

4.2 Examination of Welded Joints

4.2.1 Every welded joint in carbon steel or stainless steel piping shall be visually examined after completion and before the joint is insulated, buried, enclosed, or otherwise made inaccessible.
4.2.2 Visual examination shall confirm full weld profile, complete fusion to the base metal on both sides, and freedom from cracks, undercut, overlap, and surface porosity.
4.2.3 Nondestructive examination beyond visual shall be performed by the method indicated in the datasheet.
Nondestructive Examination Method for Welded Jointsselect
Visual examination only
Visual examination and random radiographic examination
Visual examination and random ultrasonic examination
4.2.4 Where a random examination method is selected, the proportion of welded joints examined shall be as indicated in the datasheet, distributed across welders and across each day's production rather than concentrated in one run.
Random Examination Rate for Welded Jointsrange
%
251020100
NOTE ASME B31.9 requires visual examination as the baseline for building services piping, so a project that specifies radiographic or ultrasonic examination is buying confidence beyond the code minimum. Where the piping is concealed behind permanent construction, runs above occupied space that cannot be shut down, or serves a facility where an outage carries an operational penalty, the added examination buys back the cost of a failure that could not otherwise be found until the system is filled. (4.2.5)
4.2.6 A joint that fails examination shall be repaired or cut out and remade, and the repaired or remade joint shall be re-examined by the same method.
4.2.7 The Contractor shall bear the cost of examining, repairing, and re-examining a joint that fails examination.
4.2.8 Where the proportion of examined joints that fail exceeds ten percent for any welder, all joints made by that welder since the last passing examination shall be examined at the Contractor's expense.

4.3 Brazed and Soldered Joint Acceptance

4.3.1 Each completed brazed joint shall show a continuous fillet of filler metal around the full circumference at the mouth of the socket.
4.3.2 Each completed soldered joint shall show a continuous solder bead around the full circumference at the mouth of the socket, with no gap and no evidence of unmelted solder.
4.3.3 A joint showing voids, incomplete fill, or interrupted flow of filler metal shall be cut out and remade rather than reheated and refilled.
NOTE Reheating a joint that did not fill on the first attempt rarely draws filler the rest of the way into the capillary gap, because the flux is already spent and the oxide film that blocked the flow has grown. The remake is a repair the system can be tested against; the reheat is a joint that passes the test and fails in service. (4.3.4)
4.3.5 Flux residue shall be washed from the exterior of every fluxed joint with hot water after the joint cools.

4.4 Grooved Coupling System Single-Source Responsibility

4.4.1 Where grooved mechanical joints are used, the couplings, grooved fittings, gaskets, and grooving tooling for a given pipe size and service shall be the products of a single manufacturer.
4.4.2 Grooved coupling components from different manufacturers shall not be combined in one joint.
NOTE The groove geometry, the housing casting, and the gasket cross-section of a grooved joint are a matched set whose sealing depends on the gasket being compressed a specific amount by a specific housing against a specific groove depth. Components that individually meet AWWA C606 can still combine into a joint that never reaches its designed compression. (4.4.3)

5 System Design Conditions

5.1 Design Temperatures and Pressures

5.1.1 The design operating temperature and pressure of each hydronic system govern pipe wall selection, fitting and flange pressure class, gasket compound, polymer derating, and the pressure test target, and shall be as indicated in the datasheets below.
Heating Hot Water Design Supply Temperaturerange
°F
100120140160180200220250
Per drawings — the mechanical equipment schedule (deferred by default)
Chilled Water Design Supply Temperaturerange
°F
343840424446505560
Per drawings — the mechanical equipment schedule (deferred by default)
Condenser Water Design Supply Temperaturerange
°F
556575859095100110
Per drawings — the mechanical equipment schedule (deferred by default)
Heating Hot Water Maximum Design Pressurerange
psig
305075100125150160
Per drawings — the mechanical equipment schedule (deferred by default)
Chilled Water Maximum Design Pressurerange
psig
305075100125150
Per drawings — the mechanical equipment schedule (deferred by default)
Condenser Water Maximum Design Pressurerange
psig
305075100125150
Per drawings — the mechanical equipment schedule (deferred by default)
NOTE Design temperature and pressure are outputs of the system design, not properties of the pipe, which is why they are deferred to the equipment schedule rather than defaulted here. A standard that asserts a supply temperature has decided the plant. (5.1.2)
5.1.3 The Contractor shall not select a pipe wall, fitting class, flange class, or gasket compound rated below the design pressure at the design temperature of the system in which it is installed.
5.1.4 Where a component's pressure rating derates with temperature, the rating at the design temperature shall govern, not the rating at ambient.

5.2 Freeze Protection

5.2.1 The freeze protection method for the hydronic systems shall be as indicated in the datasheet.
Freeze Protection Methodradio
○ None required
○ Glycol solution
○ Electric heat tracing
○ Seasonal drainage of exposed sections
NOTE No freeze protection method is the norm across projects, because the answer follows the climate and the routing rather than the piping system. Where piping is entirely within conditioned space, no protection is required; where a run crosses an unconditioned garage in a cold climate, glycol or tracing is unavoidable. (5.2.2)
5.2.3 Where any portion of a hydronic system is routed through a space that can fall below 35°F, the freeze protection method selected in the datasheet shall be applied to that portion.
5.2.4 Where the Contractor identifies a routing that exposes piping to freezing conditions and is not covered by the selected freeze protection method, the Contractor shall notify the Engineer of Record in writing before installing that portion.
5.2.5 Where glycol is used, the glycol type shall be as indicated in the datasheet.
Glycol Typeradio
● Inhibited propylene glycol
○ Inhibited ethylene glycol
○ Not applicable - no glycol in the system
5.2.6 Where glycol is used, the concentration by volume shall be as indicated in the datasheet.
Glycol Concentration by Volumerange
% by volume
2025303540455060
Per drawings — the mechanical equipment schedule (deferred by default)
NOTE Glycol concentration follows the local design freeze temperature with a margin, so it belongs to the project rather than to the standard. Both glycols carry a heat-transfer and pumping-power penalty that rises with concentration, and both require an inhibitor package that uninhibited automotive glycol does not have. Where a system serves a space subject to potable or food contact, propylene glycol is selected because ethylene glycol is toxic if ingested. (5.2.7)
5.2.8 Glycol solutions shall be inhibited formulations intended for closed hydronic service, and uninhibited or automotive glycol shall not be used.
5.2.9 Where glycol is used, every gasket, sealing element, and packing in the system shall be confirmed compatible with the glycol type and concentration selected.
5.2.10 Where glycol is used, the Contractor shall verify the delivered concentration by refractometer at fill and shall record the reading.

6 Pipe Materials by Service and Size

6.1 Material Selection by Service Class

6.1.1 The pipe material for each service class and size band shall be as indicated in the datasheets below.
Pipe Material - Heating Hot Water and Dual-Temperature, NPS 2 and Smallerselect
Copper water tube
Carbon steel
Stainless steel
Crosslinked polyethylene (PEX)
Polypropylene-random (PP-R)
Pipe Material - Heating Hot Water and Dual-Temperature, NPS 2½ and Largerselect
Carbon steel
Copper water tube
Stainless steel
Polypropylene-random (PP-R)
Pipe Material - Chilled Water and Condenser Water, NPS 2 and Smallerselect
Copper water tube
Carbon steel
Stainless steel
Chlorinated polyvinyl chloride (CPVC)
Polypropylene-random (PP-R)
Pipe Material - Chilled Water and Condenser Water, NPS 2½ and Largerselect
Carbon steel
Copper water tube
Stainless steel
Polypropylene-random (PP-R)
NOTE The size band split at NPS 2 is where the economics of the joint change. Below it, a copper tube joint is made by one worker with a torch or a press tool in a few minutes and no hot-work permit is needed for a press joint; above it, the wall thickness and the handling weight favor a welded or grooved steel joint that a crew makes on a rack. That is why the same building routinely uses one material for its mains and another for its runouts, and why the two decisions are recorded separately here. (6.1.2)
NOTE Heating and chilled service are separated because the failure modes differ. Hot service drives the temperature limit of polymers and elastomers and puts the joint through repeated thermal cycles; cold service puts the outside of the pipe below the dew point, so the controlling risk moves from the joint to the continuity of the vapor barrier over it. (6.1.3)
6.1.4 Where the datasheet selects the same material for both size bands of a service, the size-band break shall not be used as a reason to change material mid-run, and any material transition shall occur at a fitting or flange indicated on the coordination drawings.
6.1.5 All pipe and tube shall be new, shall bear the marking required by its material standard, and shall be free of rust scale, pitting, dents, kinks, and cracks.
6.1.6 Reconditioned, previously installed, or salvaged pipe shall not be used.
6.1.7 Galvanized steel pipe shall not be used in any closed hydronic system under this standard.
NOTE Zinc from a galvanized surface dissolves into closed-loop water, plates out on heat-transfer surfaces, and consumes the corrosion inhibitor package the water treatment program depends on. In a closed loop the zinc has nowhere to go, so the effect accumulates rather than flushing away. This is a chemistry constraint, not a preference, which is why the datasheet does not offer galvanized steel as a material. (6.1.8)

6.2 Carbon Steel Pipe

6.2.1 Carbon steel pipe shall conform to ASTM A53 / A53M Grade B, seamless or electric-resistance-welded, or to ASTM A106 / A106M Grade B, seamless.
6.2.2 Carbon steel pipe dimensions and wall schedules shall conform to ASME B36.10M.
6.2.3 The carbon steel wall schedule for each size band shall be as indicated in the datasheets below.
Carbon Steel Wall Schedule - NPS 2 and Smallerselect
Schedule 40
Schedule 80
Not applicable - no carbon steel in this size band
Carbon Steel Wall Schedule - NPS 2½ and Largerselect
Schedule 40
Standard weight
Schedule 80
Not applicable - no carbon steel in this size band
NOTE Schedule 40 and standard weight are identical through NPS 10 and diverge above it, which is why the two appear as separate selections only in the larger size band. Where a run is threaded, the wall selection also has to survive the thread depth, so a heavier wall is chosen for threaded work at a given pressure than for welded work at the same pressure. (6.2.4)
6.2.5 Where carbon steel pipe is threaded, the remaining wall at the root of the thread shall satisfy the ASME B31.9 pressure design requirement at the system design pressure and temperature.
6.2.6 Carbon steel pipe shall be stored and handled so that mill scale is not driven into the bore and so that the ends are not deformed out of round.

6.3 Copper Tube

6.3.1 Copper water tube shall conform to ASTM B88.
6.3.2 The copper tube wall type shall be as indicated in the datasheet.
Copper Tube Wall Typeselect
Type K
Type L
Type M
6.3.3 The copper tube temper shall be as indicated in the datasheet.
Copper Tube Temperradio
● Drawn temper
○ Annealed temper
NOTE Type L is the wall that commercial hydronic work has settled on, and Type K is selected where the tube is buried, embedded, or exposed to impact, because the extra wall is corrosion and damage margin rather than pressure margin. Type M is thinner than either and carries correspondingly less of that margin. (6.3.4)
6.3.5 Unless the datasheet selects otherwise, copper tube in concealed, buried, or embedded locations shall be Type K.
NOTE Drawn-temper tube holds a straight line between supports and resists the ovalling that a press or grooved joint depends on to seal, so it is selected wherever the tube is supported on hangers. Annealed tube is selected where the run must be bent continuously rather than fitted, as in a coil buried in a slab. (6.3.6)
6.3.7 Unless the datasheet selects otherwise, copper tube installed in walls, above ceilings, and in shafts shall be drawn temper.
6.3.8 Annealed-temper copper tube shall not be joined by press-connect or grooved methods unless the joining system is listed for annealed tube.
6.3.9 Copper tube shall be cut square with a wheel cutter or a fine-tooth saw, and the burr shall be removed from the bore before the joint is made.

6.4 Stainless Steel Pipe

6.4.1 Stainless steel pipe shall conform to ASTM A312 / A312M, Type 304L or Type 316L.
6.4.2 Stainless steel pipe shall be handled with tooling that has not been used on carbon steel, and shall be stored so that it does not contact carbon steel racking, banding, or fasteners.
NOTE Free iron transferred to a stainless surface by a carbon steel wire brush, grinding wheel, or storage rack rusts in place and initiates pitting under the rust bloom. The contamination happens in the laydown yard, not in the system, and it is not visible until the pipe is wet. (6.4.3)
6.4.4 Where stainless steel piping is welded, the root of the weld shall be purged with inert gas.

6.5 Polymer Piping

6.5.1 Crosslinked polyethylene tubing shall conform to ASTM F876 and shall incorporate an oxygen diffusion barrier where the system contains ferrous components.
6.5.2 Chlorinated polyvinyl chloride pipe shall conform to ASTM F441 / F441M.
6.5.3 Pressure-rated polypropylene piping shall conform to ASTM F2389.
6.5.4 Polymer piping shall be selected using the manufacturer's published pressure-temperature derating curve at the system design temperature, and the derated rating shall be not less than the system design pressure.
NOTE Oxygen that diffuses through a bare polymer wall dissolves into the loop water and corrodes every ferrous surface it reaches, which on a hydronic system means the boiler, the pump volutes, and any steel piping downstream. A barrier layer is what makes polymer tubing compatible with a mixed-metal closed loop; without one the loop has a continuous oxygen source it cannot vent. (6.5.5)
6.5.6 Polymer piping shall be supported at the spacing published for that material and temperature rather than at the spacing used for metal pipe of the same nominal size.
6.5.7 Polymer piping shall not be installed where it is exposed to direct sunlight after installation unless the product is listed for ultraviolet exposure.
6.5.8 Polymer piping shall be protected from open flame, hot work, and welding spatter during and after installation.

7 Joining Methods

7.1 Joining Method Selection

7.1.1 The joining method for carbon steel in each size band shall be as indicated in the datasheets below.
Carbon Steel Joining Method - NPS 2 and Smallerselect
Threaded
Socket welded
Grooved mechanical coupling
Press-connect
Not applicable - no carbon steel in this size band
Carbon Steel Joining Method - NPS 2½ and Largerselect
Butt welded
Grooved mechanical coupling
Flanged
Press-connect
Not applicable - no carbon steel in this size band
NOTE Neither steel size band has a joining method that most projects would choose without discussion, so neither field carries a default. Welded joints are the strongest and the most restrained but need a hot-work permit and a qualified welder; grooved joints need neither and go together fast but introduce an elastomer into the pressure boundary at every joint; press-connect joints are the fastest of the three within their listed size range and depend entirely on the tool being calibrated and the pipe being fully inserted. Where open flame is restricted by the facility or by an occupied-building phasing plan, the two flameless methods are the ones that remain available. (7.1.2)
7.1.3 The joining method for copper tube shall be as indicated in the datasheet.
Copper Tube Joining Methodselect
Brazed
Soldered
Press-connect
Grooved mechanical coupling
7.1.5 Joining methods shall not be mixed within a continuous run except at a fitting, flange, adapter, or transition coupling listed for both methods.
7.1.6 Every transition between two joining methods shall be made with a component rated for the system design pressure at the system design temperature.

7.2 Welded Joints in Carbon Steel

7.2.1 Butt-welded joints shall have ends prepared in accordance with ASME B16.25.
7.2.2 Butt-welded joints shall be full-penetration welds.
7.2.3 Socket-welded joints shall be assembled with the pipe end withdrawn approximately 1/16 in. from the bottom of the socket before welding.
NOTE The gap at the bottom of a socket weld exists so the pipe can grow into the socket when the fillet is laid down and when the system cycles thermally. Bottomed-out pipe puts the expansion into the fillet itself, and the fillet cracks at the root where nothing can be seen. (7.2.4)
7.2.5 Tack welds shall be made by qualified welders using the qualified procedure for the production weld, and shall be fused into or removed before the production weld.
7.2.6 Welding shall not be performed when the surface to be welded is wet, when the base metal is below the preheat temperature required by the qualified procedure, or in weather that prevents the shielding gas or flux from protecting the arc.
7.2.7 The Contractor shall provide fire watch, shielding, and permits for all hot work, and shall bear the cost of repairing any damage caused by welding spatter, slag, or heat.

7.3 Threaded Joints in Carbon Steel

7.3.1 Pipe threads shall conform to ASME B1.20.1.
7.3.2 Threads shall be cut clean and full, and shall be reamed to remove the burr from the bore before assembly.
7.3.3 Thread sealant shall be polytetrafluoroethylene tape or an anaerobic thread sealant listed for hydronic service at the system design temperature.
7.3.4 Thread compounds containing lead shall not be used.
7.3.5 Sealant shall be applied to the male thread only, and shall be kept back from the first thread so that it is not extruded into the bore.
NOTE Sealant extruded into the bore travels to the nearest strainer, control valve seat, or coil circuit and lodges there. A threaded system assembled with sealant applied generously to both halves of every joint delivers a measurable amount of that sealant to the equipment it was installed to protect. (7.3.6)
7.3.7 Threaded joints shall not be back-turned to align a fitting after the joint is made up.

7.4 Grooved Mechanical Joints

7.4.1 Grooved joints shall conform to AWWA C606, and grooved fittings of cast construction shall conform to ASTM A536.
7.4.2 Grooves shall be roll-formed or cut to the coupling manufacturer's published dimensions for the pipe material and wall, and shall be verified with the manufacturer's groove gauge.
NOTE Cut grooving removes wall, so it is limited to the pipe walls for which the coupling manufacturer publishes a cut-groove rating; roll grooving displaces wall instead of removing it and is the method available on thinner walls. The groove dimension, not the coupling, is what sets the joint's pressure rating. (7.4.3)
7.4.4 The grooved coupling gasket compound shall be as indicated in the datasheet.
Grooved Coupling Gasket Compoundselect
EPDM
Nitrile
Silicone
Fluoroelastomer
Not applicable - no grooved joints
NOTE The gasket is the pressure boundary of a grooved joint, so its compound has to match both the temperature and the chemistry of the service. EPDM holds up in hot and chilled water and is compatible with propylene and ethylene glycol at hydronic concentrations, and it is attacked by petroleum oils. Nitrile is selected where petroleum oil contamination is expected, and it has a lower upper temperature limit than EPDM. Silicone extends the upper temperature limit beyond EPDM. Fluoroelastomer is selected where a chemistry is present that attacks the other three. (7.4.5)
7.4.6 The gasket compound selected shall be rated by its manufacturer for the system design temperature and for the glycol type and concentration where glycol is used.
7.4.7 The gasket shall be lubricated with the coupling manufacturer's lubricant only, and petroleum-based lubricant shall not be used on an EPDM gasket.
7.4.8 The grooved coupling type on straight runs shall be as indicated in the datasheet.
Grooved Coupling Type on Straight Runsselect
Rigid
Flexible
NOTE A flexible grooved coupling permits angular and axial movement at every joint. Used deliberately at a defined location it accommodates vibration, seismic drift, or a designed movement; used as the default coupling along a long run it turns the whole run into a chain of small hinges that wanders under thermal load and works the gaskets. Where flexible couplings are used to accommodate movement, they are located and guided as part of the expansion design rather than distributed along the run. (7.4.9)
7.4.10 Unless the datasheet selects flexible couplings, flexible couplings shall be used only at locations designated on the piping coordination drawings for vibration, seismic, or expansion accommodation.
7.4.11 Flexible grooved couplings shall not be substituted for the expansion compensation required by Expansion Fittings And LoopsExpansion Fittings and Loops for PipingResolves to the current adopted revision.sync/expansion-fittings-and-loops.

7.5 Brazed and Soldered Copper Joints

7.5.1 Brazed joints shall use wrought copper braze-joint fittings conforming to ASME B16.50 or wrought copper solder-joint fittings conforming to ASME B16.22.
7.5.2 Brazing filler metal shall conform to AWS A5.8 / A5.8M.
7.5.3 Filler metal of the BCuP series may be used without flux on copper-to-copper joints, and flux shall be used on all joints between copper and a copper alloy and with all filler metal of the BAg series.
7.5.4 Cadmium-bearing brazing filler metal shall not be used.
7.5.5 Soldered joints shall use solder conforming to ASTM B32, flux conforming to ASTM B813, and the joint-making practice of ASTM B828.
7.5.6 Solder and flux containing lead shall not be used.
7.5.7 The nitrogen purge requirement during brazing shall be as indicated in the datasheet.
Nitrogen Purge During Brazingradio
● Required at all brazed joints
○ Not required
NOTE Brazing temperature is high enough to grow a black copper oxide scale on the inside of the tube, and that scale flakes off under flow and travels. Where it lands it blinds strainers, packs coil passages, and holds control valve seats off their stops. A low-flow dry nitrogen purge displaces the oxygen from the bore while the joint is hot and prevents the scale from forming, which is why most hydronic specifications require it and why it is the default here. (7.5.8)
7.5.9 Where the datasheet requires a nitrogen purge, a low-flow dry nitrogen purge shall be established through the section being brazed before heat is applied and shall be maintained until the joint cools below 300°F.
7.5.10 The purge flow shall be low enough that it does not blow the molten filler metal out of the capillary gap.
7.5.11 Joints shall be brazed or soldered with the tube fully inserted to the bottom of the socket and supported so that it does not move while the filler metal solidifies.

7.6 Press-Connect Joints

7.6.1 Press-connect fittings shall be listed for the pipe material, wall, and size in which they are installed, and for the system design pressure at the system design temperature.
7.6.2 The sealing element of a press-connect fitting shall be rated for the service temperature and for the glycol type and concentration where glycol is used.
7.6.3 Press-connect joints shall be made with the tool set and jaws specified by the fitting manufacturer for that fitting, and the tool shall be within its published calibration interval.
7.6.4 The pipe shall be marked at the manufacturer's published insertion depth before assembly, and the mark shall be verified at the fitting face before the joint is pressed.
NOTE A press joint that is not fully inserted still presses, still looks finished, and still holds a short hydrostatic test, because the sealing element can seat on the pipe without the pipe reaching the stop. It fails later under thermal cycling, when the shortened engagement lets the pipe walk out of the fitting. The insertion mark is the only field evidence that the joint was made correctly. (7.6.5)
7.6.6 Each pressed joint shall be marked by the installer to distinguish pressed from unpressed fittings during installation.
7.6.7 An unpressed fitting discovered after the system is filled shall be cut out and replaced rather than pressed in place.

7.7 Polymer Pipe Joints

7.7.1 Polymer piping shall be joined only by a joining system listed by the pipe manufacturer for that pipe.
7.7.2 Socket-fusion and butt-fusion joints in polypropylene piping shall be made with the fusion tooling, temperature, and dwell time published for the pipe and fitting being joined.
7.7.3 Solvent-cemented joints in chlorinated polyvinyl chloride piping shall use the primer and cement listed by the pipe manufacturer, and the joint shall not be pressurized until the cure time published for the ambient temperature and pipe size has elapsed.
7.7.4 Crosslinked polyethylene joints shall be made with a cold-expansion, crimp-ring, or press-sleeve system listed for the tubing, using the tool specified for that system.
7.7.5 Metallic transition fittings at polymer piping shall be supported so that the weight and the thermal movement of the metal piping are not carried by the polymer.

8 Fittings and Flanges

8.1 Carbon Steel Fittings

8.1.1 Butt-weld fittings shall conform to ASME B16.9 and shall be of ASTM A234 / A234M Grade WPB material, with a wall matching or exceeding the connecting pipe.
8.1.2 Socket-weld and threaded forged fittings shall conform to ASME B16.11, of ASTM A105 / A105M material.
8.1.3 The socket-weld forged fitting pressure class shall be as indicated in the datasheet.
Socket-Weld Forged Fitting Pressure Classrange
300060009000
8.1.4 The threaded fitting material shall be as indicated in the datasheet.
Threaded Fitting Materialselect
Malleable iron
Forged carbon steel
Cast bronze
Not applicable - no threaded joints
8.1.5 Malleable iron threaded fittings shall conform to ASME B16.3, Class 150 minimum, and shall be Class 300 where the system design pressure exceeds the Class 150 rating at the system design temperature.
8.1.6 Gray cast iron threaded fittings shall not be used in hydronic piping.
8.1.7 Reducers on horizontal runs shall be eccentric and installed flat side up, and reducers on vertical runs shall be concentric.
NOTE A concentric reducer on a horizontal run leaves a pocket at the top of the larger pipe where air collects and cannot be carried away by flow. The eccentric reducer installed flat side up keeps the top of the bore continuous so the air keeps moving toward a vent. (8.1.8)
8.1.9 Miter elbows fabricated from straight pipe shall not be used.

8.2 Copper Fittings

8.2.1 Wrought copper solder-joint fittings shall conform to ASME B16.22, and cast copper alloy solder-joint fittings shall conform to ASME B16.18.
8.2.2 Cast copper alloy flanges and flanged fittings shall conform to ASME B16.24.
8.2.3 Every copper fitting shall be rated for the system design pressure at the system design temperature.
8.2.4 Elbows and tees formed by bending or notching copper tube shall not be used in place of fittings.

8.3 Flanged Connections

8.3.1 Steel flanges shall conform to ASME B16.5, of ASTM A105 / A105M material.
8.3.2 The steel flange pressure class shall be as indicated in the datasheet.
Steel Flange Pressure Classrange
150300400600
8.3.3 The steel flange facing shall be as indicated in the datasheet.
Steel Flange Facingselect
Raised face
Flat face
8.3.4 The flange gasket material shall be as indicated in the datasheet.
Flange Gasket Materialselect
Non-asbestos compressed fiber
EPDM rubber
Flexible graphite
Polytetrafluoroethylene
8.3.5 Flange gaskets shall conform to ASME B16.21 and shall be rated for the system design temperature and for the glycol type and concentration where glycol is used.
8.3.6 Where a steel flange mates to a cast iron flange, the joint shall use a flat-face flange and a full-face gasket on the steel side.
NOTE A raised-face steel flange bolted to a flat-faced cast iron flange bends the cast iron over the edge of the raised face as the bolts are drawn up, and cast iron has almost no ductility to absorb that bending. The crack usually appears at the pump or the strainer body rather than at the flange the installer was watching. (8.3.7)
8.3.8 Flange bolts shall be tightened in a crossing pattern in at least three passes to the torque published for the gasket.
8.3.9 Flange joints shall be aligned before bolting, and bolts shall not be used to pull misaligned flanges together.

8.4 Branch Connections

8.4.1 The branch connection method in carbon steel piping shall be as indicated in the datasheet.
Branch Connection Method in Carbon Steel Pipingselect
Tee fittings
Integrally reinforced branch outlet fittings
Grooved mechanical branch outlet fittings
Not applicable - no carbon steel piping
8.4.2 Branch connections made by cutting an opening in the run pipe and welding an unreinforced nipple or coupling over it shall not be used.
NOTE An unreinforced fabricated branch removes metal from the run pipe at exactly the point where the branch load is introduced, and nothing replaces the removed area. The listed outlet fitting exists because it carries that reinforcement in its own body, which is what lets ASME B31.9 accept it without a separate area-replacement calculation. (8.4.3)
8.4.4 Branch connections in copper tube shall be made with wrought tee fittings or with mechanically extracted outlets listed for the tube size and wall.
8.4.5 Branch outlets shall be taken from the top or the side of a horizontal main, and shall not be taken from the bottom.

9 Dissimilar-Metal Isolation

9.1 Where copper or copper alloy piping connects to carbon steel piping, to a cast iron body, or to a steel-bodied item of equipment, a dissimilar-metal isolation fitting shall be installed at the connection.
9.2 The dissimilar-metal isolation method for each size band shall be as indicated in the datasheets below.
Dissimilar-Metal Isolation Method - NPS 2 and Smallerselect
Dielectric union
Dielectric nipple
Brass or bronze adapter
Not applicable - piping and equipment are a single metal
Dissimilar-Metal Isolation Method - NPS 2½ and Largerselect
Insulating flange kit
Dielectric waterway flange
Not applicable - piping and equipment are a single metal
9.3 An insulating flange kit shall comprise a full-face insulating gasket, insulating sleeves on every bolt, and insulating washers under every nut and bolt head on one side of the joint.
NOTE An insulating flange kit that omits the bolt sleeves leaves every bolt as a metallic bridge across the gasket, so the joint is electrically continuous and the isolation the kit was bought for does not exist. The failure is invisible after assembly and is the reason the sleeve count belongs in the specification rather than in the installer's judgment. (9.4)
9.5 Dissimilar-metal isolation fittings shall be rated for the system design pressure at the system design temperature.
9.6 The insulating barrier of each isolation fitting shall be inspected before installation, and a fitting with a cracked, chipped, or deformed barrier shall be rejected.
9.7 Isolation fittings shall be installed so that they remain accessible for inspection and replacement.

10 Delivery, Storage, and Handling

10.1 Pipe, tube, and fittings shall be delivered with the manufacturer's markings intact and legible.
10.2 Pipe and tube ends shall be capped or plugged at the mill or at the point of fabrication and shall remain closed until the moment the joint is made.
10.3 Pipe and tube shall be stored off the ground on continuous supports, in a manner that prevents standing water inside the bore and prevents permanent bending between supports.
10.4 Gaskets, sealing elements, and solvent cements shall be stored within the temperature range published by their manufacturer and shall not be used after their marked expiration date.
10.5 Copper tube and stainless steel pipe shall be stored so that they do not contact carbon steel racking, banding, or fasteners.
10.6 Open piping at the end of each work period shall be capped, plugged, or taped closed.
NOTE An uncapped riser is a drain for everything that falls in a mechanical shaft, and the debris that enters it is not discovered until it reaches a strainer or a control valve after the system is filled. The cost of finding it then is far greater than the cost of the cap. (10.7)
10.8 The Contractor shall bear the cost of cleaning or replacing material that was damaged or contaminated by improper storage or handling.

11 Piping Installation

11.1 Routing, Pitch, and Alignment

11.1.1 Piping shall be installed along the routing shown on the mechanical piping plans and on the accepted coordination drawings.
11.1.2 Pipe sizes shall be as shown on the mechanical piping plans.
11.1.3 The Contractor shall not install a pipe smaller than the size shown without the written approval of the Engineer of Record.
NOTE Pipe size is set by the system design against pump head, balancing authority, velocity noise limits, and whatever future load the designer reserved for. A substitution justified on the pressure drop of a single circuit does not see the rest of that reasoning, and the consequences show up as an unbalanceable branch or a velocity noise complaint after occupancy. (11.1.4)
11.1.5 The minimum runout size to a terminal unit shall be as indicated in the datasheet, regardless of any smaller size that a velocity or pressure drop calculation would permit.
Minimum Terminal Unit Runout Sizerange
in. NPS
0.50.7511.251.52
11.1.6 Piping shall be installed plumb, level, and parallel to the building structure, and runs shall be aligned with adjacent piping in the same rack.
11.1.7 Horizontal mains and branches shall pitch continuously toward the low point serving them at not less than the slope indicated in the datasheet.
Minimum Horizontal Pitchrange
in. per ft
0.06250.1250.25
NOTE Continuous pitch is what lets a hydronic system move its own air to a vent and its own water to a drain without help. Where the structure or a coordination conflict makes continuous pitch impossible, the run stops being self-clearing and every local high and low point it creates has to be given a vent or a drain of its own. (11.1.8)
11.1.9 Where continuous pitch cannot be achieved, every local high point created shall be provided with a vent connection and every local low point with a drain connection.
11.1.10 Piping shall not be sprung, forced, or pulled into position to meet an equipment connection or a hanger.

11.2 Penetrations and Sleeves

11.2.1 Piping passing through a wall, floor, or ceiling shall pass through a sleeve sized at least two nominal pipe sizes larger than the outside diameter of the pipe including its insulation.
11.2.2 Sleeves shall be set flush with the finished surface on each side, except where a sleeve is extended above a floor to resist water entry.
11.2.3 Pipe shall be centered in the sleeve and shall not bear on it, and the pipe shall be independently supported on both sides of the penetration.
11.2.4 The annular space at a penetration through a fire-rated or smoke-rated assembly shall be closed with a firestop system listed for that assembly, that pipe material, and that annular dimension.
11.2.5 Escutcheons shall be installed at penetrations exposed to view in finished spaces.

11.3 Drain and Vent Provisions

11.3.1 A drain connection with a valve shall be provided at every low point in the piping, at the base of every riser, and between every pair of equipment isolation valves.
11.3.2 The minimum drain valve size shall be as indicated in the datasheet.
Minimum Drain Valve Sizerange
in. NPS
0.50.7511.251.52
11.3.3 A plugged nipple, a capped tee, or a valveless tapping shall not be used in place of a drain valve.
11.3.4 A vent connection shall be provided at every high point in the piping, including high points created by an offset around a structural member or a duct.
11.3.5 The vent connection at a high point that is concealed above a finished ceiling or otherwise inaccessible shall be extended by tubing to an accessible location.
NOTE A vent installed near a high point rather than at it vents the pipe down to the vent and leaves the air above it, which is why an offset over a beam that was never drawn as a high point is one of the more common sources of an air-bound circuit. The vent has to be at the actual apex of the installed run, not the apex of the drawn run. (11.3.6)
11.3.7 The vent and drain devices themselves are furnished under Expansion Tanks And Air SeparatorsExpansion Tanks and Air SeparatorsResolves to the current adopted revision.sync/expansion-tanks-and-air-separators and Hydronic SpecialtiesHydronic SpecialtiesResolves to the current adopted revision.sync/hydronic-specialties; this standard requires the connections and their locations.

11.4 Equipment Connections

11.4.1 Every connection to an item of equipment shall include a removable joint that permits the equipment to be disconnected and removed without cutting pipe.
11.4.2 The removable joint type at equipment connections shall be as indicated in the datasheets below.
Removable Joint at Equipment Connections - NPS 2 and Smallerselect
Union
Flanged
Grooved coupling
Removable Joint at Equipment Connections - NPS 2½ and Largerselect
Flanged
Grooved coupling
11.4.3 Piping at an equipment connection shall be supported independently of the equipment so that no piping weight or thermal load is carried by the equipment nozzle.
11.4.4 Piping shall be aligned to the equipment nozzle before the connection is made, and the connection shall not be used to draw the piping into alignment.
NOTE A pump volute, a coil header, and a heat exchanger nozzle are cast or brazed connections with a published allowable load, and a misaligned pipe applies a moment to that connection every hour the system operates. The leak that follows is usually blamed on the equipment. (11.4.5)
11.4.6 Connections to equipment shall be made in the sequence and with the isolation arrangement shown on the mechanical piping plans.

11.5 Component Accessibility

11.5.1 Valves, isolation fittings, vents, drains, unions, and flanged joints shall be located so that they can be reached and operated without removing permanent construction.
11.5.2 Where a component is located above a hard ceiling or behind a permanent wall finish, an access panel sized for the service operation shall be provided.
11.5.3 The Contractor shall coordinate access panel locations with the trade installing the finish, and shall record every concealed valve, joint, and vent location on the as-built drawings.
11.5.4 Where the parties disagree whether a component is reachable for the operation it requires, the Engineer of Record shall make the initial determination.

12 Support, Anchor, and Expansion Interfaces

12.1 Hanger and Support Interface

12.1.1 Hangers, supports, structural attachments, and seismic bracing for hydronic piping shall be furnished and installed in accordance with Hangers And SupportsHangers and Supports for Mechanical Piping and EquipmentResolves to the current adopted revision.sync/hangers-and-supports and MSS SP-58.
12.1.2 The Contractor shall establish support locations before piping is installed, and shall not use an installed pipe to locate a support.
12.1.3 Support spacing for each pipe material and size shall follow Hangers And SupportsHangers and Supports for Mechanical Piping and EquipmentResolves to the current adopted revision.sync/hangers-and-supports, and shall be reduced where a valve, flange, strainer, or specialty item concentrates weight between supports.
NOTE Copper tube requires closer support spacing than steel pipe of the same nominal size because it is markedly less stiff. Sag between supports traps air at the low side of each bay and concentrates bending stress at the fittings, both of which are hidden once the insulation is on. (12.1.4)
12.1.5 Insulated piping shall be supported on insulation shields or insulated supports sized for the insulation outside diameter, and no hanger shall bear directly on insulation.
12.1.6 Where the parties disagree whether a support arrangement is adequate for a concentrated load, the Engineer of Record shall make the initial determination.

12.2 Thermal Expansion Interface

12.2.1 The Contractor shall install the expansion compensation, anchors, and guides shown on the mechanical piping plans in accordance with Expansion Fittings And LoopsExpansion Fittings and Loops for PipingResolves to the current adopted revision.sync/expansion-fittings-and-loops.
12.2.2 Anchor and guide locations shall not be relocated or omitted without the written approval of the Engineer of Record.
NOTE Carbon steel expands about 0.0075 in. per foot per 100°F of temperature rise, so a 200 ft heating main installed at 70°F and operated at 180°F grows roughly 1.6 in. over its length. Copper grows about 0.011 in. per foot per 100°F, so the same run in copper grows roughly half again as much. Those numbers are why a heating distribution main cannot simply be clamped at both ends. (12.2.3)
NOTE The expansion design is a force path between anchors, and a relocated anchor changes the movement every guide and every loop between it and the next anchor was sized for. Moving one anchor to clear a conflict invalidates the compensation on both sides of it, which is why the relocation is an engineering decision rather than a field one. (12.2.4)
12.2.5 Where a conflict prevents installing an anchor or a guide at the location shown, the Contractor shall report the conflict to the Engineer of Record before proceeding with that run.

13 Valve, Specialty, and Air-Management Interfaces

13.1 General-duty isolation, shutoff, and throttling valves shall be furnished and installed in accordance with HVAC Piping ValvesGeneral-Duty Valves for HVAC PipingResolves to the current adopted revision.sync/hvac-piping-valves.
13.2 Balancing valves, pressure-independent control valves, strainers, flexible connectors, gauges, and thermometers shall be furnished and installed in accordance with Hydronic SpecialtiesHydronic SpecialtiesResolves to the current adopted revision.sync/hydronic-specialties.
13.3 Expansion tanks, air separators, dirt separators, and automatic air vents shall be furnished and installed in accordance with Expansion Tanks And Air SeparatorsExpansion Tanks and Air SeparatorsResolves to the current adopted revision.sync/expansion-tanks-and-air-separators.
13.4 The piping shall provide an isolation valve connection on each side of every item of equipment, at the base and top of every riser, on every branch serving more than two terminal units, and at every terminal unit connection.
13.5 The piping shall provide the connection, orientation, and clearance each specialty item requires, including the straight run of pipe upstream and downstream that the item's manufacturer publishes.
NOTE A balancing device is a flow-measuring instrument as well as a throttle, and its published accuracy assumes a developed velocity profile at its inlet. Installing it directly downstream of an elbow or a tee gives it a swirling profile it cannot read correctly, so the balance is set against a measurement that is wrong by an amount nobody can see. (13.6)
13.7 Balancing devices shall be installed on the return side of each terminal unit.
13.8 Where an item of equipment or a specialty is set before the piping is complete, the Contractor shall protect its connections from construction debris until the connection is made.
NOTE Terminal unit and central plant equipment themselves are outside this standard; the piping connections to them are within it. (13.9)

14 Insulation and Identification Interfaces

14.1 Insulation Interface

14.1.1 Pipe, fitting, valve, and equipment insulation shall be furnished and installed in accordance with Mechanical InsulationMechanical InsulationResolves to the current adopted revision.sync/mechanical-insulation and shall meet the minimum thickness required by the adopted edition of ANSI/ASHRAE/IES 90.1.
14.1.2 Insulation shall not be applied to any portion of the piping until that portion has passed its pressure test and the test has been documented.
14.1.3 The pipe surface shall be clean, dry, and free of loose rust and scale when insulation is applied.
NOTE Insulation applied over a wet or corroding surface seals the moisture against the pipe and removes the only condition under which the corrosion would have stopped. On chilled water the same detail also saturates the insulation, so the thermal performance the project paid for is gone before the building opens. (14.1.4)
14.1.5 The Contractor shall complete all joints, connections, and repairs on a run before the insulation contractor is released to that run.
14.1.6 Where a joint must be opened after insulation is applied, the Contractor shall bear the cost of removing and reinstating the insulation and the vapor retarder.
14.1.7 The continuity of the vapor retarder over fittings, valves, flanges, and supports on below-ambient piping is required by Mechanical InsulationMechanical InsulationResolves to the current adopted revision.sync/mechanical-insulation; this standard requires that the piping be presented in a condition that allows that continuity to be achieved.

14.2 Identification Interface

14.2.1 Pipe markers, flow direction indicators, and valve tags shall be furnished and installed in accordance with Mechanical IdentificationMechanical IdentificationResolves to the current adopted revision.sync/mechanical-identification and ASME A13.1.
14.2.2 Piping shall be identified after insulation is complete and before the ceiling or shaft enclosure is closed.
14.2.3 Valves, fittings, flanges, and unions shall bear the manufacturer's markings required by MSS SP-25, and those markings shall remain legible and visible after installation where the component is accessible.

15 Cleaning, Flushing, and Water Treatment Interface

15.1 Cleaning, flushing, passivation, and the corrosion inhibitor start charge shall be performed in accordance with Hydronic Cleaning And FlushingHydronic System Cleaning and FlushingResolves to the current adopted revision.sync/hydronic-cleaning-and-flushing, and the ongoing treatment program shall be established in accordance with HVAC Water TreatmentHVAC Water TreatmentResolves to the current adopted revision.sync/hvac-water-treatment.
15.2 The Contractor shall keep the interior of the piping clean during installation and shall not rely on flushing to remove construction debris that could have been kept out.
15.3 Strainer screens, control valves, and coils shall be protected or bypassed before flushing, in the arrangement required by Hydronic Cleaning And FlushingHydronic System Cleaning and FlushingResolves to the current adopted revision.sync/hydronic-cleaning-and-flushing.
15.4 The piping shall be complete, pressure tested, and accepted before the cleaning and flushing sequence begins.
NOTE The sequence matters in one direction only: the pressure test proves the assembly, the cleaning and flushing prepare the water, and the insulation closes the work. Running the test after the system has been chemically treated means a leak discharges treated water and the boundary has to be re-established; running the insulation before the test means finding a leak through a jacket. (15.5)
15.6 Where a leak repair is made after cleaning and flushing are complete, the Contractor shall re-flush the affected section and shall bear the cost of the re-flush and of any treatment chemical lost.
15.7 The Contractor shall provide the fill, drain, and temporary connection points that the cleaning and flushing procedure requires, at the locations shown on the mechanical piping plans.

16 Pressure Testing

16.1 Test Medium and Boundaries

16.1.1 Every portion of the hydronic piping shall be pressure tested before it is insulated, concealed, buried, or enclosed.
16.1.2 The pressure test medium shall be as indicated in the datasheet.
Pressure Test Mediumradio
● Hydrostatic, using clean water
○ Pneumatic, using clean dry air or nitrogen
NOTE Water is nearly incompressible, so a hydrostatic test stores almost no energy and a joint that lets go releases water at the rate the pump can supply. A gas at the same pressure stores enough elastic energy that the same failure becomes a projectile hazard, which is why the hydrostatic test is the baseline and the pneumatic test is reserved for situations where water cannot be used, such as a pre-insulated system that cannot be wet-tested or piping over finished work where a discharge would be more damaging than the test is useful. (16.1.3)
16.1.4 The test pressure shall be 1.5 times the maximum system design pressure and not less than 100 psig, in accordance with ASME B31.9 and the International Mechanical Code Chapter 12.
16.1.5 Where the calculated test pressure exceeds the rating of a component within the intended boundary, that component shall be isolated or removed from the boundary and shall be tested separately at its own rated pressure.
16.1.6 The pressure test staging shall be as indicated in the datasheet.
Pressure Test Stagingselect
Sectional test of each portion as it is completed
Single test of the completed system
Sectional tests followed by a final test of the completed system
NOTE Sectional testing is what allows concealed work to close on schedule, because a section can be tested and released as soon as it is complete rather than waiting for the whole system. Where the system is small enough to complete in one sequence, or where every joint stays accessible until the end, a single test of the whole system is simpler and proves the same thing. (16.1.7)
16.1.8 Every test boundary shall be recorded on the pressure test plan before the test is performed.
16.1.9 A pneumatic test shall be preceded by a preliminary test at 25 psig to find gross leaks by sound, and shall not exceed the lowest pressure rating of any component within the boundary.
16.1.10 Personnel not essential to a pneumatic test shall be excluded from the test area while the system is pressurized.

16.2 Test Procedure and Acceptance

16.2.1 The system shall be filled from its lowest point with air vented continuously from every high point until the boundary is full of the test medium.
16.2.2 The test pressure shall be applied and held for not less than the duration indicated in the datasheet.
Minimum Test Hold Durationrange
hours
12481224
16.2.3 The pressure loss over the hold period shall not exceed the value indicated in the datasheet.
Maximum Permitted Pressure Loss During the Holdrange
psi
2510
NOTE A zero-loss criterion is achievable on a hydrostatic test of a stable system and is the reason hydrostatic testing is trusted. On a long hold, on a pneumatic test, or where the boundary spans a large temperature swing between day and night, thermal effects on the medium can produce a reading that is not a leak, and an allowance keeps the criterion honest. Where an allowance is used, a temperature reading at the start and end of the hold is what separates a thermal change from a leak. (16.2.4)
16.2.5 Where a pressure loss allowance greater than zero is selected, the temperature of the test medium shall be recorded at the start and at the end of the hold period.
16.2.6 Every joint, fitting, weld, braze, flange, and valve body within the boundary shall be visually inspected during the hold period.
16.2.7 Visible leakage at any joint shall fail the test regardless of the measured pressure loss.
16.2.8 A failed test shall be followed by repair of the cause, restoration of the boundary, and a complete repeat of the test from the beginning.
16.2.9 The Contractor shall bear the cost of the repair, the retest, the test medium, and the repair of any other trade's work damaged by the failure or by the water released.
16.2.10 Test gauges shall be calibrated within the preceding twelve months, shall have a full-scale range between 1.5 and 2 times the test pressure, and shall be graduated finely enough to resolve a change of 5 psi.
NOTE A gauge reading in the bottom fifth of its scale cannot resolve the change the test is looking for, and a gauge reading near full scale has no margin. Ranging the gauge at 1.5 to 2 times the test pressure puts the reading in the part of the dial where the instrument is accurate. (16.2.11)
16.2.12 The test gauge shall be located at the low point of the test boundary, and a reading taken at the pump or at a high point shall not be used as the sole basis for acceptance.

16.3 Test Documentation

16.3.1 The pressure test shall be witnessed by the party indicated in the datasheet.
Pressure Test Witnessselect
Engineer of Record or the Engineer's representative
Owner's commissioning authority
Authority Having Jurisdiction inspector
Contractor's quality control representative
16.3.2 The Contractor shall give the witnessing party not less than five business days notice of a scheduled test.
16.3.3 A signed and dated test report shall be prepared for every test boundary, recording the date, the boundary, the medium, the test pressure, the hold duration, the starting and ending pressure, the temperature readings where required, the name and signature of the Contractor's representative, and the name and signature of the witness.
16.3.4 A test report shall record a pass only where the pressure loss was within the permitted value and no leakage was found by visual inspection.
16.3.5 A test report shall not record a conditional or qualified pass, and a boundary in which a repair was made shall be recorded on a new report covering the complete repeat test.

17 Warranty

17.1 The Contractor shall warrant the hydronic piping work, including pipe, fittings, joints, welds, brazes, soldered joints, pressed joints, flanged joints, and isolation fittings, against defects in materials and workmanship for the period indicated in the datasheet, measured from the date of substantial completion.
Contractor Installation Warranty Periodrange
years
1235
17.2 Where the contract General Conditions specify a longer warranty period than the datasheet, the longer period shall govern.
17.3 Any leak, joint failure, or corrosion attributable to the installation discovered within the warranty period shall be repaired by the Contractor at no cost to the Owner.
17.4 The Contractor shall bear the cost of removing and reinstating insulation, ceiling, and finish work required to reach a warranted repair, and the cost of repairing damage caused by the failure or by the repair itself.
NOTE The unassigned cost in a piping warranty is almost never the joint. It is the ceiling that has to come down to reach it, the insulation that has to be rebuilt over it, and the finishes below that the leak reached first. Naming those costs here is what makes the warranty enforceable without an argument. (17.5)
17.6 A repaired or replaced portion of the piping shall carry a warranty running for a full new term from the date the repair is accepted, or for the remainder of the original term, whichever ends later.
17.7 The Contractor shall pressure test any repaired portion in accordance with this standard before the repair is accepted.

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"Hydronic Piping." SynC Standards. Licensed under CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/). Source: https://synergyinconstruction.com/wiki/sync/hydronic-piping — reference material only; not professional engineering advice and provided without warranty. Verify against governing codes and have a licensed professional review before use.