+---
+title: Hydronic System Cleaning and Flushing
+category: Mechanical / Controls & Testing
+toc_depth: 3
+description: >
+ When to use: The construction-phase procedure the installing mechanical
+ contractor follows to clean, flush, and passivate closed hydronic
+ distribution systems (heating hot water, chilled water, dual-temperature,
+ condenser water, and glycol-protected loops) before TAB begins and before
+ the ongoing water treatment program is placed online. Covers system filling
+ and fill-pressure verification, temporary flush bypasses around sensitive
+ equipment, external flush-pump connection, alkaline or TSP cleaning
+ circulation, high-velocity mechanical flushing, flush-water disposal
+ coordination, acceptance testing (turbidity, iron, TSS, pH, conductivity),
+ corrosion-inhibitor start charge and passivation circulation, corrosion
+ coupon installation, and the signed cleaning, flushing, and passivation
+ report that hands off to the water treatment provider and TAB contractor.
+ Applies to new construction and to renovation or retro-commissioning where
+ existing systems are re-entered or extended, at any size and in any pipe
+ material.
+ Not intended for: the ongoing chemical water treatment program, inhibitor
+ dosing, side-stream filtration, and ASHRAE 188 water management planning
+ (use [[sync/hvac-water-treatment]]); hydronic pipe material selection,
+ joining, supports, and structural pressure testing per ASME B31.9 (use
+ [[sync/hydronic-piping]]); third-party air and water balancing (use
+ [[sync/testing-adjusting-and-balancing]]); functional performance testing
+ and controls checkout (use [[sync/commissioning]]); domestic water
+ disinfection (use [[sync/domestic-water-piping]]); fire sprinkler flushing
+ and hydrostatic testing (use [[sync/common-work-results-fire-suppression]]);
+ steam boiler waterside cleaning and layup (governed by ASME BPVC Section I);
+ and pump selection and trim (use [[sync/hvac-pumps]]).
+---
+
+# Scope {toc}
+
+## This standard governs the construction-phase cleaning, high-velocity flushing, and chemical passivation of closed hydronic distribution systems, performed by the installing mechanical contractor after the piping passes its hydrostatic pressure test and before the system is balanced or placed in chemical service. {note}
+
+## Closed hydronic systems within scope include heating hot water (HHW), chilled water (CHW), dual-temperature, condenser water, and inhibited-glycol loops, in carbon steel, copper, or grooved-mechanical piping, at any system size. {note}
+
+## The work of this standard ends at acceptance of passivation and delivery of the signed cleaning, flushing, and passivation report; the ongoing chemical treatment program described in [[sync/hvac-water-treatment]] takes over from that point. {note}
+
+## This standard owns the construction-phase execution sequence the piping contractor works to. The pre-operational cleaning rationale and the long-term chemistry are owned by [[sync/hvac-water-treatment]]; the two are complementary and shall be read together. {note}
+
+## The Contractor shall not begin cleaning operations until the hydronic piping has passed and the Engineer of Record has witnessed the hydrostatic pressure test required by [[sync/hydronic-piping]] and ASME B31.9.
+
+## Cleaning, flushing, and passivation shall be complete and accepted before the testing, adjusting, and balancing (TAB) contractor begins balancing under [[sync/testing-adjusting-and-balancing]].
+
+## Cleaning, flushing, and passivation acceptance shall be a documented prerequisite to functional performance testing under [[sync/commissioning]].
+
+# Referenced Standards {toc}
+
+## Equipment, materials, and execution 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.
+
+## BSRIA BG 29 is cited as an industry reference guide for velocity selection, method-statement content, and acceptance criteria; it is not a mandatory compliance document on US projects. {note}
+
+| Standard | Title |
+|----------|-------|
+| ASME B31.9 | Building Services Piping |
+| ANSI/ASHRAE Standard 188 | Legionellosis: Risk Management for Building Water Systems |
+| ASHRAE Guideline 12 | Managing the Risk of Legionellosis Associated with Building Water Systems |
+| ASHRAE Guideline 0 | The Commissioning Process |
+| ASHRAE Handbook | HVAC Systems and Equipment (Hydronic Heating and Cooling) |
+| ASTM D3370 | Sampling Water from Closed Conduits |
+| ASTM D2688 | Corrosivity of Water in the Absence of Heat Transfer (Weight Loss Methods) |
+| ASTM D1193 | Reagent Water |
+| ASTM D4012 | Adenosine Triphosphate (ATP) Content of Microorganisms in Water |
+| NFPA 13 | Installation of Sprinkler Systems |
+| NSF/ANSI 60 | Drinking Water Treatment Chemicals - Health Effects |
+| OSHA 29 CFR 1910.1200 | Hazard Communication Standard |
+| EPA FIFRA | Federal Insecticide, Fungicide, and Rodenticide Act |
+| IMC Chapter 12 | International Mechanical Code - Hydronic Piping |
+| BSRIA BG 29 | Pre-Commission Cleaning of Pipework Systems |
+
+# Submittals {toc}
+
+## Action Submittals {note}
+
+### Action submittals establish the planned method before any chemical is brought to site, so the Owner and Engineer can confirm velocity feasibility, chemical compatibility, bypass arrangement, and discharge route in advance of the work. {note}
+
+### Specifying the cleaning scope only as a line item inside the piping section, with no method statement or acceptance criteria, lets subcontractors price the work without planning it. This standard requires a dedicated, reviewed method statement. {note}
+
+### The Contractor shall submit the following action items for review before mobilizing the cleaning operation:
+
+- Cleaning and flushing method statement describing fill, cleaning chemistry, flush sequence, bypass arrangement, and reinstatement
+- Velocity calculation demonstrating that every pipe section reaches the minimum flush velocity, identifying sections that require an external flush pump or targeted jumpers
+- Flush-pump plan identifying system pumps versus external flush pump, with flow and head for the section being flushed
+- Temporary bypass and strainer schedule listing every coil, plate heat exchanger, control valve, and balancing valve to be bypassed or strainer-protected
+- Chemical product data and Safety Data Sheets for cleaner, passivation inhibitor, and glycol, with NSF/ANSI 60 status where make-up water contact is possible
+- Flush-water discharge plan with the local sewer authority's written acceptance, neutralization method, and any off-site disposal manifest
+
+```datasheet
+label: Action submittals required before mobilization
+type: checkbox
+options:
+ - Cleaning and flushing method statement
+ - Flush velocity calculation (all sections)
+ - Flush-pump plan (system vs. external)
+ - Temporary bypass and strainer schedule
+ - Chemical product data and SDS
+ - Flush-water discharge plan with authority acceptance
+default:
+ - Cleaning and flushing method statement
+ - Flush velocity calculation (all sections)
+ - Flush-pump plan (system vs. external)
+ - Temporary bypass and strainer schedule
+ - Chemical product data and SDS
+ - Flush-water discharge plan with authority acceptance
+```
+
+## Closeout Submittals {note}
+
+### The closeout submittals are the documentation baseline the Owner relies on for the water treatment program and for any future coil warranty claim; without them there is no evidence that cleaning was performed. {note}
+
+### The Contractor shall submit the following closeout items before final acceptance:
+
+- Signed cleaning and flushing report including flush start and finish, velocity achieved, and number of passes
+- Flush acceptance test results for turbidity, total iron, TSS, pH, and conductivity at each sample point
+- Signed passivation report including inhibitor type, dose multiplier, circulation temperature, and circulation duration
+- Corrosion coupon installation record listing coupon metallurgy and rack locations
+- Photographic flush-color log at the defined sampling intervals
+- Glycol charge record (glycol systems only) with pre-charge water chemistry and post-charge concentration
+
+```datasheet
+label: Closeout submittals required for final acceptance
+type: checkbox
+options:
+ - Signed cleaning and flushing report
+ - Flush acceptance test results (turbidity, iron, TSS, pH, conductivity)
+ - Signed passivation report
+ - Corrosion coupon installation record
+ - Photographic flush-color log
+ - Glycol charge record (glycol systems)
+default:
+ - Signed cleaning and flushing report
+ - Flush acceptance test results (turbidity, iron, TSS, pH, conductivity)
+ - Signed passivation report
+ - Corrosion coupon installation record
+ - Photographic flush-color log
+```
+
+## Informational Submittals {note}
+
+### The Contractor shall submit the following informational items:
+
+- Qualifications of the specialty cleaning subcontractor or water treatment service provider performing or witnessing the work
+- Rental flush-pump skid data sheet where an external pump is used
+- Laboratory certification for any off-site flush-water analysis
+
+```datasheet
+label: Informational submittals
+type: checkbox
+options:
+ - Cleaning subcontractor / treatment provider qualifications
+ - External flush-pump skid data sheet
+ - Laboratory certification for flush-water analysis
+default:
+ - Cleaning subcontractor / treatment provider qualifications
+```
+
+# Quality Assurance {toc}
+
+## Responsibility Assignment {note}
+
+### Ambiguity over who performs the cleaning - the piping contractor, an Owner-furnished water treatment provider, or a specialty cleaning subcontractor - creates responsibility gaps and schedule conflicts with TAB and commissioning. The responsible party shall be named before the work begins. {note}
+
+### The Contract Documents shall name a single party responsible for cleaning, flushing, and passivation, with the witnessing party identified separately.
+
+```datasheet
+label: Party responsible for cleaning, flushing, and passivation
+type: radio
+options:
+ - Installing mechanical (piping) contractor
+ - Specialty cleaning subcontractor to the mechanical contractor
+ - Owner-furnished water treatment service provider
+default: Installing mechanical (piping) contractor
+```
+
+```datasheet
+label: Party witnessing flush and passivation acceptance
+type: radio
+options:
+ - Engineer of Record
+ - Commissioning authority
+ - Owner's water treatment service provider
+ - Owner's representative
+default: Commissioning authority
+```
+
+## Coordination {note}
+
+### The flushing operation sits between three other trades, and the most common project failure is starting TAB or commissioning before flushing is accepted, which fouls coils that then must be back-flushed after balancing. {note}
+
+### The Contractor shall coordinate the cleaning sequence so that flush acceptance precedes TAB mobilization and so that passivation completion precedes placing the chemical program online.
+
+### The TAB contractor shall refuse to begin balancing until the signed flushing report is in hand.
+
+### Flushing operations shall not pressurize, cross-connect, or contaminate adjacent fire sprinkler piping, consistent with the separation principles of NFPA 13.
+
+## Chemical Handling {note}
+
+### All cleaning chemicals, degreasers, acid cleaners, and passivation inhibitors brought to site shall be labeled and accompanied by Safety Data Sheets in accordance with OSHA 29 CFR 1910.1200.
+
+### Any biocidal product used for biological knockdown of an open condenser water system shall be EPA-registered under FIFRA for the intended use.
+
+### Where a cleaning or passivation chemical may contact domestic make-up water, the chemical shall be certified to NSF/ANSI 60 or the make-up connection shall be physically isolated during the operation.
+
+# Environmental and Service Conditions {toc}
+
+## Pre-Cleaning System Condition {note}
+
+### Construction debris in a new hydronic system includes mill scale, weld spatter, cutting oils, thread-cutting lubricant, jointing compound, and general trash; the purpose of cleaning and flushing is to remove this material before it lodges in coils, exchangers, and valve seats. {note}
+
+### Copper oxide scale formed inside brazed joints made without a nitrogen purge flakes off during high-velocity flushing and recirculates into finned coil tubes, where it cannot be flushed out and causes sustained heat-transfer loss. {note}
+
+### Brazed copper joints shall have been made with a nitrogen purge per [[sync/hydronic-piping]]; joints made without a purge shall be reported to the Engineer before flushing.
+
+## System Type {note}
+
+### The cleaning chemistry, flush velocity target, and passivation temperature all depend on the system type and dominant metallurgy, which shall be identified before selecting the method. {note}
+
+```datasheet
+label: Hydronic system type
+type: radio
+options:
+ - Heating hot water (HHW)
+ - Chilled water (CHW)
+ - Dual-temperature
+ - Condenser water (closed)
+ - Inhibited-glycol loop
+default: Chilled water (CHW)
+```
+
+```datasheet
+label: Dominant system metallurgy
+type: radio
+options:
+ - Carbon steel
+ - Copper
+ - Mixed carbon steel and copper
+default: Mixed carbon steel and copper
+```
+
+# System Filling and Pressure Verification {toc}
+
+## Filling {note}
+
+### The system is filled with clean make-up water and brought to fill pressure so that the pre-cleaning condition - leak-free and at a known baseline chemistry - is confirmed before any chemical is added. {note}
+
+### The system shall be filled with potable or treated make-up water and vented at all high points until air-free.
+
+### Fill water chemistry (pH and conductivity) shall be recorded at filling to serve as the baseline against which flush acceptance is judged.
+
+### Initial fill pressure shall be verified and recorded after venting and confirmed stable before cleaning chemistry is introduced.
+
+```datasheet
+label: System design working pressure
+type: range
+unit: psig
+min: 50
+max: 300
+step: 5
+default: 125
+```
+
+```datasheet
+label: Hydrostatic test pressure (1.5x design, witnessed before cleaning)
+type: range
+unit: psig
+min: 75
+max: 450
+step: 5
+default: 188
+```
+
+```datasheet
+label: Hydrostatic test hold duration
+type: range
+unit: min
+min: 30
+max: 240
+step: 30
+default: 30
+```
+
+# Temporary Bypasses and Equipment Protection {toc}
+
+## Sensitive Equipment Isolation {note}
+
+### Debris mobilized at flushing velocity damages coil tubes, scores control valve seats, and clogs plate heat exchanger channels. Routing flush flow through this equipment is the second most common cleaning failure, after premature TAB. {note}
+
+### Coils, plate heat exchangers, control valves, and balancing valves shall be isolated from the flush stream by spool-piece jumper bypasses or by fine-mesh temporary strainers installed immediately upstream, before high-velocity flushing begins.
+
+### Spool-piece jumpers shall be fabricated from the same pipe material as the run they replace and fitted with isolation valves at each end.
+
+### Where temporary strainers are used instead of jumpers, they shall be 100 mesh or finer stainless steel and shall be inspected and cleaned between flush passes.
+
+```datasheet
+label: Sensitive-equipment protection method
+type: radio
+options:
+ - Spool-piece jumper bypass (most thorough)
+ - Temporary fine-mesh strainer upstream (100 mesh or finer)
+ - Combination by equipment type
+default: Spool-piece jumper bypass (most thorough)
+```
+
+```datasheet
+label: Temporary strainer mesh (where strainers used)
+type: select
+options:
+ - 100 mesh
+ - 150 mesh
+ - 200 mesh
+default: 100 mesh
+unit: mesh
+```
+
+## Dead Legs and Branch Ends {note}
+
+### Debris accumulates in uncirculated sections and migrates back into the cleaned system once interconnecting valves are opened for service. Every dead leg and branch-end service needs a temporary jumper or end-of-line flush connection. {note}
+
+### Every dead leg and branch-end service shall be provided with a temporary drain-and-fill jumper or an end-of-line flush connection so it is circulated during flushing.
+
+### The complete interconnected loop, including both carbon steel and copper sections, shall be flushed as one system; sections shall not be flushed in permanently isolated groups.
+
+# Cleaning Chemistry and Circulation {toc}
+
+## Cleaning Method Selection {note}
+
+### The cleaning method is selected from the dominant contamination: an alkaline degreaser handles cutting oils and general construction soil on most new systems; trisodium phosphate (TSP) is a commodity alternative; an acid clean is reserved for heavy mill scale or weld discoloration; and a mechanical-only flush is acceptable for small all-copper systems. {note}
+
+### Acid cleaning shall be used only where heavy mill scale or weld discoloration is present in the piping.
+
+### Acid-cleaner spent solution shall be neutralized on site or removed off-site for disposal.
+
+```datasheet
+label: Cleaning method
+type: radio
+options:
+ - Alkaline degreaser circulation
+ - Trisodium phosphate (TSP) flush
+ - Acid clean (heavy mill scale only)
+ - Mechanical-only flush (small all-copper systems)
+default: Alkaline degreaser circulation
+```
+
+## Alkaline Degreaser Parameters {note}
+
+### The alkaline degreaser is dosed into the filled system and circulated warm to lift cutting oils and construction soil into suspension before the mechanical flush carries them out. {note}
+
+### The alkaline degreaser shall be circulated at the concentration, temperature, and duration scheduled below, with all valves open to circulate the full loop.
+
+```datasheet
+label: Alkaline degreaser concentration (by volume in fill water)
+type: range
+unit: '%'
+min: 2
+max: 5
+step: 0.5
+default: 3
+```
+
+```datasheet
+label: Cleaning circulation temperature
+type: range
+unit: °F
+min: 70
+max: 140
+step: 5
+default: 70
+```
+
+```datasheet
+label: Cleaning circulation duration
+type: range
+unit: h
+min: 12
+max: 48
+step: 12
+default: 24
+```
+
+## TSP Alternative Parameters {note}
+
+### Trisodium phosphate is restricted for sanitary discharge in some jurisdictions; where TSP is used, the discharge plan shall confirm acceptance before the clean begins. {note}
+
+```datasheet
+label: TSP concentration (by weight)
+type: range
+unit: '%'
+min: 0.3
+max: 0.7
+step: 0.1
+default: 0.5
+```
+
+```datasheet
+label: TSP circulation duration
+type: range
+unit: h
+min: 12
+max: 24
+step: 6
+default: 18
+```
+
+# High-Velocity Flushing {toc}
+
+## Flush Velocity {note}
+
+### The minimum flush velocity is the industry-consensus 5 ft/s for carbon steel; 6 to 8 ft/s is preferred and usually achievable in mains. The contractor demonstrates by calculation that every pipe section reaches the minimum, adding targeted jumpers at dead legs that the main flush cannot reach. {note}
+
+### Flushing shall achieve a minimum velocity of 5 ft/s in every pipe section, demonstrated by the submitted velocity calculation.
+
+### Mains shall be flushed at 6 to 8 ft/s where the pump and pipe size permit.
+
+### Sections that cannot reach 5 ft/s under main flush flow shall be flushed individually through targeted jumpers until the minimum is met.
+
+```datasheet
+label: Minimum flush velocity (every section)
+type: range
+unit: ft/s
+min: 5
+max: 8
+step: 0.5
+default: 5
+```
+
+```datasheet
+label: Preferred main flush velocity
+type: range
+unit: ft/s
+min: 6
+max: 8
+step: 0.5
+default: 7
+```
+
+## Flush Pump Source {note}
+
+### System pumps are selected for design flow at design head, not for high-velocity low-head flushing, so on larger systems they cannot reach 5 ft/s with all valves open. An external high-volume flush pump is then required for the cleaning operation. {note}
+
+### Where the system pumps cannot achieve the minimum flush velocity with all balancing and control valves wide open, a temporary external flush pump shall be connected for the flushing operation.
+
+### The external flush pump shall be sized to deliver 1.5 to 2 times normal operating flow in the section being flushed, with suction strainer, discharge manifold, and flow measurement.
+
+```datasheet
+label: Flush pump source
+type: radio
+options:
+ - System circulation pumps (velocity verified by calculation)
+ - Temporary external high-volume flush pump
+ - System pumps for mains, external pump for high-resistance branches
+default: System circulation pumps (velocity verified by calculation)
+```
+
+```datasheet
+label: External flush pump capacity
+type: range
+unit: GPM
+min: 100
+max: 600
+step: 50
+default: 350
+```
+
+```datasheet
+label: Flush flow multiple of normal operating flow (section being flushed)
+type: range
+unit: x
+min: 1.5
+max: 2
+step: 0.1
+default: 1.7
+```
+
+## Flush Color Monitoring {note}
+
+### Flush water is sampled at intervals at the flush drains and its color and clarity logged photographically; the trend from turbid to clear is the visible evidence that debris is being removed. {note}
+
+### Flush-drain water shall be visually sampled and photographed at intervals until clarity reaches the tap-water surrogate standard, with the log included in the closeout package.
+
+```datasheet
+label: Flush-color sampling interval
+type: select
+options:
+ - Every 10 minutes
+ - Every 15 minutes
+ - Every 30 minutes
+default: Every 15 minutes
+```
+
+# Flush Water Disposal {toc}
+
+## Discharge Coordination {note}
+
+### Alkaline cleaner discharges can violate local sewer pretreatment limits, and acid-cleaner discharges almost always require neutralization or off-site disposal. The discharge route must be coordinated with the local authority before the clean begins, not after. {note}
+
+### The Contractor shall obtain written acceptance of the flush-water discharge route from the local sewer authority before introducing cleaning chemistry.
+
+### Discharge to sanitary sewer shall be neutralized to a pH of 6 to 9 before release where required by the authority having jurisdiction.
+
+### Acid-cleaner residue and biocide-bearing water shall be neutralized or removed off-site as regulated waste, with disposal manifests retained.
+
+```datasheet
+label: Flush water discharge route
+type: radio
+options:
+ - Direct to sanitary sewer (authority-approved)
+ - Neutralized to pH 6-9 before sanitary discharge
+ - Off-site disposal as regulated waste
+default: Neutralized to pH 6-9 before sanitary discharge
+```
+
+```datasheet
+label: Discharge pH neutralization band
+type: range
+unit: pH
+min: 6
+max: 9
+step: 0.5
+setpoints:
+ - 6
+ - 9
+default: 7
+```
+
+# Flush Acceptance Testing {toc}
+
+## Acceptance Criteria {note}
+
+### Flush acceptance moves from a visual clarity check, through field turbidity measurement, to laboratory analysis for total iron and total suspended solids, depending on the rigor the owner requires. Iron and TSS confirm debris removal; pH and conductivity returning near the make-up baseline confirm the cleaner itself has been rinsed out. {note}
+
+### Persistent total iron above 2 mg/L after multiple passes indicates an active corrosion source rather than construction debris, and shall be investigated before acceptance rather than flushed indefinitely. {note}
+
+### Water samples shall be collected per ASTM D3370 from the lowest system sample point and from each major zone.
+
+### Field chemistry tests shall use reagent water of ASTM D1193 Type II minimum purity.
+
+### The flush shall be accepted only when total iron, total suspended solids, pH, and conductivity all meet the scheduled criteria.
+
+```datasheet
+label: Flush acceptance protocol
+type: radio
+options:
+ - Visual clarity only
+ - Field turbidity measurement
+ - Laboratory total iron and TSS analysis
+default: Field turbidity measurement
+```
+
+```datasheet
+label: Flush acceptance - total iron limit
+type: range
+unit: mg/L
+min: 0.5
+max: 2
+step: 0.1
+default: 1
+```
+
+```datasheet
+label: Flush acceptance - total suspended solids (TSS) limit
+type: range
+unit: mg/L
+min: 5
+max: 25
+step: 5
+default: 5
+```
+
+```datasheet
+label: Flush acceptance - pH within band of make-up water
+type: range
+unit: pH units
+min: 0.3
+max: 1
+step: 0.1
+default: 0.5
+```
+
+```datasheet
+label: Flush acceptance - conductivity within band of make-up water
+type: range
+unit: µS/cm
+min: 100
+max: 300
+step: 50
+default: 200
+```
+
+```datasheet
+label: Open condenser water - ATP microbiological baseline (ASTM D4012)
+type: radio
+options:
+ - Required before chemical program online
+ - Not required (closed system)
+default: Not required (closed system)
+```
+
+# Passivation {toc}
+
+## Passivation Timing {note}
+
+### Freshly cleaned carbon steel flash-rusts within hours in oxygen-bearing water, so passivation cannot wait. The inhibitor must be charged and circulation started the same day flush acceptance is achieved. {note}
+
+### Adding the long-term water treatment program at its normal operating concentration before passivation is complete will not build a dense passive film, because the operating concentration is too low; passivation deliberately runs at an elevated multiple of operating concentration. {note}
+
+### The corrosion inhibitor start charge shall be added and passivation circulation shall begin on the same day flush acceptance is achieved.
+
+### The long-term chemical program of [[sync/hvac-water-treatment]] shall not be placed online until passivation is accepted.
+
+## Passivation Chemistry {note}
+
+### Passivation chemistry must match the long-term water treatment program: molybdate, nitrite, or a molybdate-nitrite blend for carbon steel and mixed metallurgy, and a phosphonate-azole-polymer approach where aluminum is present. Choosing a passivation chemistry incompatible with the program forces a chemistry change at start-up. {note}
+
+### The passivation inhibitor chemistry shall match the long-term program chemistry specified in [[sync/hvac-water-treatment]].
+
+```datasheet
+label: Passivation chemistry
+type: radio
+options:
+ - Molybdate-based
+ - Nitrite-based
+ - Molybdate-nitrite blend
+ - Phosphonate-azole-polymer (mixed metallurgy / aluminum)
+default: Molybdate-nitrite blend
+```
+
+```datasheet
+label: Passivation dose multiplier (x long-term operating concentration)
+type: range
+unit: x
+min: 1.5
+max: 5
+step: 0.5
+default: 2.5
+```
+
+```datasheet
+label: Molybdate passivation target (as MoO4 2-)
+type: range
+unit: mg/L
+min: 500
+max: 1000
+step: 50
+default: 750
+```
+
+```datasheet
+label: Nitrite passivation target (as NO2-)
+type: range
+unit: mg/L
+min: 1500
+max: 2400
+step: 100
+default: 1900
+```
+
+## Passivation Circulation {note}
+
+### Carbon steel mains need a longer passivation circulation than copper-dominant systems to build the film; HHW systems are circulated warm toward operating temperature, while CHW and condenser water systems can only run at ambient with the pumps on. {note}
+
+### Passivation circulation shall continue for the scheduled duration with the inhibitor maintained within the passivation target band.
+
+### HHW systems shall be passivated at elevated temperature approaching operating temperature; CHW and condenser water systems shall be passivated at ambient temperature with pumps running.
+
+```datasheet
+label: Passivation circulation duration
+type: range
+unit: h
+min: 12
+max: 168
+step: 12
+default: 48
+```
+
+```datasheet
+label: Passivation circulation temperature - HHW
+type: range
+unit: °F
+min: 100
+max: 180
+step: 10
+default: 120
+```
+
+```datasheet
+label: Passivation circulation temperature - CHW / condenser water
+type: range
+unit: °F
+min: 60
+max: 80
+step: 5
+default: 70
+```
+
+# Corrosion Coupons {toc}
+
+## Coupon Installation {note}
+
+### Corrosion coupons are the physical evidence trail that passivation worked; without them there is no objective data to distinguish a well-passivated system from one whose chemical program is merely holding corrosion in check at higher ongoing cost. {note}
+
+### A corrosion coupon rack holding the system's representative metallurgies shall be installed in a flowing stream in each zone of the system at the start of passivation.
+
+### Coupons shall include carbon steel and, where copper is present, copper, matching the system metallurgy.
+
+### Coupons shall be first read at 90 days per ASTM D2688, with subsequent reads at 6 months and annually, by the water treatment provider under [[sync/hvac-water-treatment]].
+
+```datasheet
+label: Corrosion coupon metallurgies installed
+type: checkbox
+options:
+ - Carbon steel
+ - Copper
+ - Admiralty brass
+ - Galvanized steel
+default:
+ - Carbon steel
+ - Copper
+```
+
+```datasheet
+label: Number of coupon rack locations
+type: range
+unit: locations
+min: 1
+max: 6
+step: 1
+default: 2
+```
+
+```datasheet
+label: First coupon read interval (ASTM D2688)
+type: select
+options:
+ - 30 days
+ - 60 days
+ - 90 days
+default: 90 days
+unit: days
+```
+
+# Glycol Systems {toc}
+
+## Glycol Charge Sequence {note}
+
+### On glycol loops the sequencing is explicit: clean and flush with water only, accept the flush, drain 100 percent of the flush water, then charge inhibited glycol at design concentration. Charging glycol into a dirty system embeds construction debris in the glycol where it cannot be flushed out without a full dump and re-clean, and cleaning with glycol in the system wastes expensive fluid and can degrade its inhibitor package. {note}
+
+### Automotive antifreeze shall not be used; its inhibitor package is not optimized for long-term hydronic service and its dyes and bittering agents interfere with field chemistry tests. {note}
+
+### Glycol systems shall be cleaned and flushed with water only; glycol shall not be present during cleaning.
+
+### One hundred percent of the flush water shall be drained after flush acceptance before glycol is charged.
+
+### The system shall be charged with inhibited industrial-grade glycol at the design concentration after flush acceptance and drain-down.
+
+### Pre-charge water chemistry and post-charge glycol concentration shall both be recorded in the glycol charge record.
+
+```datasheet
+label: Glycol type
+type: radio
+options:
+ - Inhibited industrial-grade propylene glycol
+ - Inhibited industrial-grade ethylene glycol
+default: Inhibited industrial-grade propylene glycol
+```
+
+```datasheet
+label: Design glycol concentration (by volume)
+type: range
+unit: '%'
+min: 20
+max: 50
+step: 5
+default: 35
+```
+
+# Reinstatement and Acceptance {toc}
+
+## System Reinstatement {note}
+
+### After flushing and passivation, the temporary bypasses come out and the protected equipment is returned to service; any temporary strainers must be removed or cleaned so they do not become a permanent restriction. {note}
+
+### All spool-piece jumpers and temporary flush connections shall be removed and the permanent piping, coils, exchangers, and valves reinstated.
+
+### Temporary flush strainers shall be removed, or cleaned and confirmed clear, before the system is returned to service.
+
+### Permanent strainers and basket filters shall be inspected and cleaned after the first 48 hours of operation following reinstatement.
+
+## Acceptance and Hand-Off {note}
+
+### The signed cleaning, flushing, and passivation report is the trigger that hands the system off to the water treatment provider and clears the TAB contractor to begin. {note}
+
+### The Contractor shall deliver the signed cleaning, flushing, and passivation report, with all acceptance test results and the coupon installation record, as the documented hand-off to the water treatment provider and TAB contractor.
+
+```datasheet
+label: Acceptance documentation level
+type: radio
+options:
+ - Signed flushing and passivation reports only
+ - Reports plus full laboratory iron, TSS, and pH results
+ - Reports, laboratory results, and photographic flush-color log
+default: Reports plus full laboratory iron, TSS, and pH results
+```
+
+# Warranty {toc}
+
+## The Contractor shall warrant that the system was cleaned, flushed, and passivated in accordance with the accepted method statement and that the documented acceptance criteria were met.
+
+## Coil and heat-exchanger fouling traceable to omitted or incomplete flushing shall be corrected by the Contractor at no cost to the Owner during the warranty period.
+
+```datasheet
+label: Cleaning and flushing workmanship warranty period
+type: range
+unit: months
+min: 12
+max: 24
+step: 6
+default: 12
+```
+
+# Spare Parts {toc}
+
+## The Contractor shall turn over unused corrosion coupons of each installed metallurgy for the first scheduled coupon change-out.
+
+## The Contractor shall provide the Owner with the chemical product data and Safety Data Sheets for the passivation inhibitor and glycol in service.
+
+```datasheet
+label: Spare corrosion coupon sets turned over
+type: range
+unit: sets
+min: 0
+max: 4
+step: 1
+default: 1
+```