HVAC Water Treatment
Corpus sync: neutrality remakes, note hygiene, datasheet relocation, transformer-split cross-refs
Showing changes from Rev 7
to Rev 8
in HVAC Water Treatment.
---
title: HVAC Water Treatment
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### For chemically treated systems, the minimum backflow protection device is typically a reduced-pressure principle backflow prevention assembly (RPBA) conforming to ASSE 1013; many jurisdictions specifically require RPBA on open cooling tower make-up because the chemistry contains biocides registered under FIFRA. {note}
+### Make-up water connections to all treated systems shall be protected by backflow prevention assemblies of the type and rating required by the adopted plumbing code and the local cross-connection control authority.
+
```datasheet
label: Make-up Water Backflow Prevention
…6 unchanged lines
```
−### Make-up water connections to all treated systems shall be protected by backflow prevention assemblies of the type and rating required by the adopted plumbing code and the local cross-connection control authority.
−
### Treated water shall not be permitted to flow back into the domestic supply at any operating condition.
…139 unchanged lines
### Most projects use an alkaline degreasing circulation followed by extended high-velocity mechanical flushing. {note}
+### The cleaning method shall be selected based on the predominant material of construction, the system's geometry, and the anticipated nature and quantity of construction debris.
+
```datasheet
label: Pre-Operational Cleaning Method — Closed Systems
…7 unchanged lines
```
−```datasheet
−label: Pre-Operational Cleaning Method — Open Condenser Water Systems
−type: select
−options:
− - "Alkaline degreaser circulation through cooling tower basin and piping, high-velocity flush"
− - "Alkaline degreaser plus oxidizing biocide (initial microbial knockdown) followed by flush"
− - "Mechanical flushing followed by direct online passivation (small towers with clean piping)"
−default: "Alkaline degreaser plus oxidizing biocide (initial microbial knockdown) followed by flush"
−```
−
−### The cleaning method shall be selected based on the predominant material of construction, the system's geometry, and the anticipated nature and quantity of construction debris.
−
### The historical method using trisodium phosphate (TSP) at approximately 0.5% by weight, circulated at operating temperature, remains acceptable for small systems and for all-copper systems where cutting oil and brazing flux residue are the only significant contaminants. {note}
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### A new open system shall receive both a chemical degreasing step for construction oils and dust and an oxidizing biocide pre-treatment for biological knockdown before the system is placed in service with its long-term chemistry.
+```datasheet
+label: Pre-Operational Cleaning Method — Open Condenser Water Systems
+type: select
+options:
+ - "Alkaline degreaser circulation through cooling tower basin and piping, high-velocity flush"
+ - "Alkaline degreaser plus oxidizing biocide (initial microbial knockdown) followed by flush"
+ - "Mechanical flushing followed by direct online passivation (small towers with clean piping)"
+default: "Alkaline degreaser plus oxidizing biocide (initial microbial knockdown) followed by flush"
+```
+
### Pre-operational biocide treatment shall be timed so that any chlorine or bromine residual is dissipated before the long-term inhibitor and biocide program begins, to avoid chemistry interference.
…3 unchanged lines
### Debris that settles in a corner at 3 ft/s requires 6 to 8 ft/s to lift and carry, achieved either by running the system pumps with all balancing and control valves wide open and temporary bypasses around coils, or by using a temporary high-volume flush pump connected at the central plant. {note}
+### The Contractor shall demonstrate by calculation that the planned flush arrangement produces a minimum velocity of 5 ft/s in every pipe section to be flushed, with 6 to 8 ft/s preferred where attainable.
+
```datasheet
label: Minimum Flushing Velocity
…7 unchanged lines
```
+### The flush shall continue until the water at the system's lowest point (the drain valve or designated sample port) runs visibly clear and the suspended solids and iron measurements are within the acceptance criteria.
+
```datasheet
label: Flush Acceptance Criteria
…8 unchanged lines
```
−### The Contractor shall demonstrate by calculation that the planned flush arrangement produces a minimum velocity of 5 ft/s in every pipe section to be flushed, with 6 to 8 ft/s preferred where attainable.
−
−### The flush shall continue until the water at the system's lowest point (the drain valve or designated sample port) runs visibly clear and the suspended solids and iron measurements are within the acceptance criteria.
−
### A flush that does not reach the acceptance criteria after a full circulation pattern shall be repeated.
…20 unchanged lines
### Flush water carries cleaner chemistry, mobilized debris, and possibly elevated iron and copper. {note}
+### The Contractor shall coordinate discharge with the local sanitary sewer authority and shall obtain any required discharge permit before flushing.
+
```datasheet
label: Flush Water Discharge Route
…8 unchanged lines
```
−### The Contractor shall coordinate discharge with the local sanitary sewer authority and shall obtain any required discharge permit before flushing.
−
### Discharge directly to storm sewer is generally prohibited because of the cleaner chemistry and metals content. {note}
…4 unchanged lines
# Pre-Passivation {toc}
−## Purpose {toc}
+## Once the system has been cleaned of construction debris and flushed clear, the metal surfaces are bright and active — chemically reactive and ready to either form a stable protective oxide layer (passivation) or to begin corroding. {note}
−### Once the system has been cleaned of construction debris and flushed clear, the metal surfaces are bright and active — chemically reactive and ready to either form a stable protective oxide layer (passivation) or to begin corroding. {note}
+## The window between completion of flushing and the establishment of a stable passive layer is short — within hours, freshly exposed carbon steel begins to flash-rust if exposed to oxygen-bearing water without inhibitor present. {note}
−### The window between completion of flushing and the establishment of a stable passive layer is short — within hours, freshly exposed carbon steel begins to flash-rust if exposed to oxygen-bearing water without inhibitor present. {note}
+## Pre-passivation establishes the protective oxide layer under controlled conditions, with the system intentionally dosed at higher inhibitor concentration than the long-term operating level, circulating at a specific temperature for a specific time. {note}
−### Pre-passivation establishes the protective oxide layer under controlled conditions, with the system intentionally dosed at higher inhibitor concentration than the long-term operating level, circulating at a specific temperature for a specific time. {note}
+## Done well, pre-passivation creates a uniform, dense protective film that resists oxygen corrosion for the life of the system; done badly or omitted, the system establishes a partial, irregular film whose unprotected zones become initiation sites for pitting that persists despite a correct long-term inhibitor concentration. {note}
−### Done well, pre-passivation creates a uniform, dense protective film that resists oxygen corrosion for the life of the system; done badly or omitted, the system establishes a partial, irregular film whose unprotected zones become initiation sites for pitting that persists despite a correct long-term inhibitor concentration. {note}
−
## Pre-Passivation Procedure — Closed Hydronic Systems {toc}
### The pre-passivation chemistry dose, circulation time, and circulation temperature are set per the datasheets below. {note}
+### After flushing acceptance and immediately before placing the system into operating service, the system shall be refilled with treated make-up water and dosed with the pre-passivation chemistry at typically 2 to 3 times the long-term operating inhibitor level.
+
```datasheet
label: Pre-Passivation Inhibitor Dose Multiplier (vs. Long-Term Operating Concentration)
…7 unchanged lines
```
+### The system shall be circulated continuously at near operating temperature — typically 100°F to 140°F for HHW systems, or ambient with circulation pumps running for CHW systems — for a minimum of 24 hours, with 48 to 72 hours preferred where carbon steel is the predominant material.
+
```datasheet
label: Pre-Passivation Circulation Time
…18 unchanged lines
```
−### After flushing acceptance and immediately before placing the system into operating service, the system shall be refilled with treated make-up water and dosed with the pre-passivation chemistry at typically 2 to 3 times the long-term operating inhibitor level.
−
−### The system shall be circulated continuously at near operating temperature — typically 100°F to 140°F for HHW systems, or ambient with circulation pumps running for CHW systems — for a minimum of 24 hours, with 48 to 72 hours preferred where carbon steel is the predominant material.
−
### During passivation, sample-port readings shall confirm that inhibitor concentration remains within the design range across the entire system, with no zones short on inhibitor due to high consumption from un-passivated surfaces.
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### Open systems are passivated more rapidly than closed systems because the higher dissolved oxygen content and the higher inhibitor circulation rate establish the protective film quickly. {note}
+### A typical open-tower passivation shall run at 1.5 to 2 times the long-term inhibitor level for 24 to 48 hours of circulation with the tower fan off or running on minimum speed to limit evaporation during passivation.
+
+### The cycles of concentration during passivation shall be intentionally held low — close to 1.5 — by elevated bleed-off, so that the passivation chemistry remains close to the dosed level and is not concentrated to a damaging level.
+
```datasheet
label: Pre-Passivation — Open System Bleed Strategy
…6 unchanged lines
```
−### A typical open-tower passivation shall run at 1.5 to 2 times the long-term inhibitor level for 24 to 48 hours of circulation with the tower fan off or running on minimum speed to limit evaporation during passivation.
−
−### The cycles of concentration during passivation shall be intentionally held low — close to 1.5 — by elevated bleed-off, so that the passivation chemistry remains close to the dosed level and is not concentrated to a damaging level.
−
# Closed System Chemical Treatment {toc}
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### The most common chemistries are molybdate, nitrite, and combinations of these with azole copper-corrosion inhibitor and polymer dispersant. {note}
+### The inhibitor program for a closed hydronic system shall be selected to match the predominant metallurgy, the operating temperature, and the Owner's preferences regarding monitoring complexity, ecological discharge concerns, and cost.
+
```datasheet
label: Closed System Primary Corrosion Inhibitor
…8 unchanged lines
```
−### The inhibitor program for a closed hydronic system shall be selected to match the predominant metallurgy, the operating temperature, and the Owner's preferences regarding monitoring complexity, ecological discharge concerns, and cost.
−
### Molybdate-based inhibitors form a passive film on carbon steel through an oxidative mechanism that does not depend on oxygen scavenging, are stable across a wide pH and temperature range, are non-toxic at use concentrations, and are not affected by chloride to the same extent nitrite is; their disadvantages are higher unit cost, the requirement for higher pH (typically 8.5 to 10.5) to protect copper, and a long-term ecological concern with molybdate discharge to surface waters in some jurisdictions. {note}
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### The azole forms a chemisorbed film on copper surfaces that inhibits both copper dissolution and the redeposition of copper ions on carbon steel (where they would act as cathodes and accelerate steel corrosion). {note}
+### Where the system contains copper or copper-alloy components, an azole copper inhibitor shall be added regardless of the primary chemistry, with tolyltriazole (TT) the standard at 5 to 15 mg/L and benzotriazole (BZT) or mercaptobenzothiazole (MBT) as alternatives.
+
```datasheet
label: Copper Corrosion Inhibitor (Azole)
…7 unchanged lines
```
−### Where the system contains copper or copper-alloy components, an azole copper inhibitor shall be added regardless of the primary chemistry, with tolyltriazole (TT) the standard at 5 to 15 mg/L and benzotriazole (BZT) or mercaptobenzothiazole (MBT) as alternatives.
−
### In any closed system where an oxidizing biocide rotation is part of the program, azole feed shall be timed to follow the biocide treatment, because azole is consumed by oxidizing biocides.
…10 unchanged lines
### The long-term operating control ranges depend on the chemistry selected; the service provider's recommendation governs the project-specific control range. {note}
+### The closed system inhibitor concentration control range shall be specified for the chemistry selected, and used as the basis for field test comparison at each service visit.
+
```datasheet
label: Closed System Control Range — Inhibitor Concentration
…8 unchanged lines
```
+### The closed system pH control range shall be specified for the chemistry selected, and used as the basis for field test comparison at each service visit.
+
```datasheet
label: Closed System pH Range
…6 unchanged lines
```
+### Whether closed system conductivity is used as a trending control parameter shall be specified.
+
```datasheet
label: Closed System Conductivity Tracking
…12 unchanged lines
### Oxidizing biocides (chlorine, bromine) are generally not used in closed systems because of their interaction with corrosion inhibitors and elastomer attack at the concentrations needed. {note}
+### A non-oxidizing biocide — typically isothiazolone, glutaraldehyde, or a quaternary ammonium compound — shall be added on a programmed rotation (typically every 90 to 180 days) where biological inhibition is required.
+
```datasheet
label: Closed System Biocide Program
…7 unchanged lines
```
−### A non-oxidizing biocide — typically isothiazolone, glutaraldehyde, or a quaternary ammonium compound — shall be added on a programmed rotation (typically every 90 to 180 days) where biological inhibition is required.
−
### The biocide rotation shall use at least two different active ingredients on alternating cycles, to suppress development of resistant organisms.
…17 unchanged lines
### The phosphonate provides threshold inhibition while the polymer modifies crystal habit and keeps suspended solids dispersed. {note}
+### The open system scale inhibitor formulation shall be specified, consistent with the make-up water silica content and any jurisdictional restriction on phosphate discharge.
+
```datasheet
label: Open System Scale Inhibitor
…12 unchanged lines
### Open system corrosion control uses lower inhibitor concentrations than closed systems because the inhibitors are continuously lost to bleed-off. {note}
+### The standard approach shall combine a phosphate or zinc-phosphate steel inhibitor at 2 to 6 mg/L (as PO4) with an azole copper inhibitor at 1 to 3 mg/L (as TT) and the polymer dispersant that supports the scale inhibitor.
+
```datasheet
label: Open System Corrosion Inhibitor
…6 unchanged lines
```
+### Where galvanized steel cooling towers are present, the pH shall be held between 7.0 and 8.0 during the first three to six months of operation while the zinc surface develops its protective patina, after which the pH range may rise to 8.0 to 9.0 for long-term operation.
+
```datasheet
label: New Galvanized Tower — Initial Operation pH (Months 1–3)
…7 unchanged lines
```
−### The standard approach shall combine a phosphate or zinc-phosphate steel inhibitor at 2 to 6 mg/L (as PO4) with an azole copper inhibitor at 1 to 3 mg/L (as TT) and the polymer dispersant that supports the scale inhibitor.
−
−### Where galvanized steel cooling towers are present, the pH shall be held between 7.0 and 8.0 during the first three to six months of operation while the zinc surface develops its protective patina, after which the pH range may rise to 8.0 to 9.0 for long-term operation.
−
### Aggressive pH excursions above 9.5 in the first weeks of operation cause rapid loss of the zinc coating and shall be prevented.
…3 unchanged lines
### The biocide program is the primary engineering control for Legionella in the cooling tower water, and its proper design and documentation is the principal mechanism by which the project demonstrates compliance with ASHRAE 188 for the open system. {note}
+### The oxidizing biocide shall be chlorine (sodium hypochlorite) or bromine (sodium bromide activated by hypochlorite, or stabilized bromine donor), and the non-oxidizing biocide shall be selected from isothiazolone, glutaraldehyde, dibromonitrilopropionamide (DBNPA), or quaternary ammonium compounds.
+
```datasheet
label: Open System Biocide Program
…19 unchanged lines
```
+### The two biocide classes shall be alternated to suppress development of resistant organisms and to maintain biocide effectiveness against the broadest range of microbial species.
+
```datasheet
label: Non-Oxidizing Biocide Rotation
…8 unchanged lines
```
−### The oxidizing biocide shall be chlorine (sodium hypochlorite) or bromine (sodium bromide activated by hypochlorite, or stabilized bromine donor), and the non-oxidizing biocide shall be selected from isothiazolone, glutaraldehyde, dibromonitrilopropionamide (DBNPA), or quaternary ammonium compounds.
−
−### The two biocide classes shall be alternated to suppress development of resistant organisms and to maintain biocide effectiveness against the broadest range of microbial species.
−
### Bromine is generally preferred over chlorine for open cooling towers operating in the typical alkaline pH range (8.0 to 9.0) because hypobromous acid (HOBr) is the dominant species at these pH values and is a more effective biocide than hypochlorous acid (HOCl), which dissociates to less-active hypochlorite (OCl-) at higher pH; chlorine remains effective and economical below pH 8.0 or where pH is intentionally controlled lower for galvanized tower protection. {note}
…45 unchanged lines
### Typical control ranges are 600 to 750 mV for active biocidal residual in the recirculating water. {note}
+### Where oxidizing biocide feed is automatically controlled, the preferred control parameter shall be oxidation-reduction potential (ORP), measured in millivolts by an in-line ORP probe.
+
+### The ORP set point shall be established by the service provider based on the specific oxidizing chemistry and verified by free halogen residual measurement at the corresponding ORP reading.
+
```datasheet
label: ORP Control Setpoint Range
…7 unchanged lines
```
−### Where oxidizing biocide feed is automatically controlled, the preferred control parameter shall be oxidation-reduction potential (ORP), measured in millivolts by an in-line ORP probe.
−
−### The ORP set point shall be established by the service provider based on the specific oxidizing chemistry and verified by free halogen residual measurement at the corresponding ORP reading.
−
### A calibration curve relating ORP to free halogen residual shall be established and verified at least quarterly.
…13 unchanged lines
### Most commercial HVAC projects use PG; EG is reserved for industrial process loops, district energy plants, and snowmelt systems where toxicity hazard is managed by the system design. {note}
+### The glycol type, propylene or ethylene, shall be specified, consistent with the toxicity hazard and heat-transfer performance required by the application.
+
```datasheet
label: Glycol Type
…13 unchanged lines
### Automotive glycol contains inhibitors selected for automotive cooling systems (copper, brass, aluminum, frequent fluid replacement) that are not optimal for a building hydronic system (carbon steel, copper, multi-year service life), and its dyes and bittering agents can interfere with field testing. {note}
−```datasheet
−label: Glycol Product Grade
−type: radio
−options:
− - "Inhibited industrial grade — pre-formulated with HVAC-appropriate inhibitors"
− - "Inhibited industrial grade plus supplemental azole and biocide rotation"
− - "Uninhibited grade — separate inhibitor program required (rare, project-specific)"
−default: "Inhibited industrial grade — pre-formulated with HVAC-appropriate inhibitors"
−```
+### The glycol concentration, by percent volume, shall be specified for this system, based on the freeze protection level required by the design conditions.
```datasheet
…11 unchanged lines
### Glycol for HVAC service shall be inhibited industrial grade — pre-formulated with corrosion inhibitors selected for hydronic service.
+```datasheet
+label: Glycol Product Grade
+type: radio
+options:
+ - "Inhibited industrial grade — pre-formulated with HVAC-appropriate inhibitors"
+ - "Inhibited industrial grade plus supplemental azole and biocide rotation"
+ - "Uninhibited grade — separate inhibitor program required (rare, project-specific)"
+default: "Inhibited industrial grade — pre-formulated with HVAC-appropriate inhibitors"
+```
+
### Uninhibited or automotive glycol shall not be used.
…5 unchanged lines
### The degradation produces organic acids that lower system pH and increase corrosion aggressiveness; the reserve alkalinity buffer in inhibited industrial glycol neutralizes these acids until it is consumed and the inhibitor package depletes. {note}
+### Glycol systems shall be tested at each service visit for pH, inhibitor reserve, and glycol concentration by refractometer.
+
```datasheet
label: Glycol System Test Parameters at Each Service Visit
…9 unchanged lines
```
−### Glycol systems shall be tested at each service visit for pH, inhibitor reserve, and glycol concentration by refractometer.
−
### When inhibitor reserve is depleted (indicated by pH drift below the design range despite stable glycol concentration), the system shall be either fully recharged with fresh inhibited glycol or supplemented with concentrated inhibitor package, per the glycol manufacturer's recommendation.
# Steam and Condensate Treatment {toc}
−## Scope {toc}
+## Steam and Condensate Program Boundaries {toc}
### The program addresses three regions of the system: the boiler water, where dissolved solids concentrate and where scale, corrosion, and carryover are controlled; the steam itself, where amines and neutralizers control condensate-line corrosion; and the condensate return, where carbonic acid attack of carbon steel return piping is the principal corrosion mechanism. {note}
…8 unchanged lines
### Cycles of concentration are managed by blowdown, either continuous (a small bleed from the surface of the boiler water) or intermittent (manual blow from the mud drum). {note}
+### The boiler feedwater pretreatment method shall be specified, consistent with the boiler operating pressure and the makeup water quality and cycles of concentration required.
+
```datasheet
label: Boiler Feedwater Pretreatment
…37 unchanged lines
### The principal aggressor in condensate is carbonic acid (H2CO3), formed when carbon dioxide released from carbonate alkalinity in the boiler water dissolves in the condensate; carbonic acid lowers condensate pH to as low as 5.0 to 5.5, aggressively attacking carbon steel condensate return piping and causing grooving corrosion at the bottom of horizontal returns where condensate collects. {note}
+### A volatile amine — typically morpholine, cyclohexylamine, or DEAE (diethylaminoethanol) — shall be added to the boiler water so that the amine volatilizes with the steam, condenses with the water, and neutralizes the carbonic acid to maintain condensate pH at 8.5 to 9.0.
+
```datasheet
label: Steam Line Amine
…8 unchanged lines
```
−### A volatile amine — typically morpholine, cyclohexylamine, or DEAE (diethylaminoethanol) — shall be added to the boiler water so that the amine volatilizes with the steam, condenses with the water, and neutralizes the carbonic acid to maintain condensate pH at 8.5 to 9.0.
−
### The selection of amine shall account for its distribution ratio (the proportion that ends up at the first vs. last condensing point) and, where the steam contacts food, for the amines allowed by FDA 21 CFR 173.310.
…2 unchanged lines
### Test parameters include pH (control range 8.5 to 9.0), conductivity (trend), and total iron (high iron indicates active return-line corrosion). {note}
+### The condensate quality control range shall be specified, consistent with the system's service application, including any food-contact steam requirement limiting amine use.
+
```datasheet
label: Condensate Quality Control Range
…17 unchanged lines
### The standard pump for HVAC water treatment service is a peristaltic, diaphragm, or solenoid-actuated metering pump with adjustable stroke length, adjustable stroke frequency, and a pulse input for pacing by water meter or controller signal. {note}
+### The chemical feed pump type shall be specified for each chemical product, consistent with the chemical's compatibility, dosing accuracy, and off-gassing characteristics.
+
```datasheet
label: Chemical Feed Pump Type
…7 unchanged lines
```
+### The pacing signal source for each chemical feed pump shall be specified, consistent with the parameter the dose is intended to track.
+
```datasheet
label: Chemical Feed Pacing Signal Source
…17 unchanged lines
### Solid (puck, tablet, briquette) chemical feeders eliminate the need for a chemical-storage room with bulk tanks and provide longer service intervals between chemical replenishment, but they offer less precise dose control and require manual top-up rather than automatic bulk-tank refilling. {note}
+### The chemical feed equipment configuration, bulk liquid or solid, shall be specified for each chemical product, consistent with the dose-control precision and service-interval needs of the project.
+
```datasheet
label: Chemical Feed Equipment — Bulk vs. Solid
…14 unchanged lines
### Modern controllers integrate conductivity measurement, ORP measurement, pH measurement (where required), water-meter pulse counting, multiple chemical-feed pump outputs, bleed-off solenoid output, alarm contacts, and a communication port (typically Modbus RTU or BACnet) to the building automation system. {note}
+### The measurement, feed-pacing, and communication capabilities required of the conductivity and ORP controller shall be specified for this installation.
+
```datasheet
label: Controller Capabilities Required
…29 unchanged lines
### A filter is side-stream because it processes a fraction of the recirculation flow (typically 5% to 10%) rather than the full flow, achieving effective particle removal over time without the pressure drop and equipment size penalty of full-flow filtration. {note}
+### The side-stream filtration type shall be specified for open systems, consistent with the particle size range and density expected in the recirculating water.
+
```datasheet
label: Side-Stream Filtration Type — Open Systems
…8 unchanged lines
```
+### Where side-stream filtration is provided on a closed system, the filtration type shall be specified, consistent with the particulate load and fineness of filtration required.
+
```datasheet
label: Side-Stream Filtration Type — Closed Systems (Where Provided)
…7 unchanged lines
```
+### The side-stream filter flow rate, as a percent of total system recirculation flow, shall be specified.
+
```datasheet
label: Side-Stream Flow Rate as Percent of System Flow
…41 unchanged lines
### The frequencies shown in the datasheets below are minimums. {note}
+### The service provider shall test the systems at the frequency below, with results recorded in the service log.
+
```datasheet
label: Service Visit Frequency — Open Systems
…27 unchanged lines
```
−### The service provider shall test the systems at the frequency below, with results recorded in the service log.
−
### More frequent testing shall be performed during start-up, after any chemistry change, after any major system upset (leak, equipment failure, repair), and during the first six months after a new system is commissioned.
…3 unchanged lines
### Weight loss is reported as mils per year (mpy) and compared against acceptance criteria. {note}
+### Whether a corrosion coupon rack is installed shall be specified for each treated system, consistent with the system type, size, and open or closed configuration.
+
```datasheet
label: Corrosion Coupon Rack Installation
…6 unchanged lines
```
+### The corrosion coupon metallurgy shall be specified for the closed system, representative of the metals and specialty equipment present in the system.
+
```datasheet
label: Coupon Metallurgy — Closed System
…7 unchanged lines
```
+### The corrosion coupon exposure period shall be specified, consistent with the monitoring purpose, whether start-up evaluation or long-term trending.
+
```datasheet
label: Coupon Exposure Period
…13 unchanged lines
### ATP testing per ASTM D4012 provides a rapid screening for total microbial load and is increasingly used as the primary in-field microbial test method because results are available in minutes rather than the 48-hour incubation required for dip slides. {note}
+### Open systems shall be monitored for microbial activity, with the minimum monitoring being dip-slide testing at each service visit for total aerobic bacteria (TAB) and action levels defined in the Water Management Plan.
+
```datasheet
label: Microbial Monitoring at Routine Service
…7 unchanged lines
```
+### Routine Legionella sampling (culture method per ISO 11731 or qPCR molecular method) shall be performed at intervals specified in the Water Management Plan, with the typical interval being quarterly for non-healthcare facilities and monthly for healthcare and high-risk facilities.
+
```datasheet
label: Legionella Sampling Frequency — Open Cooling Towers
…7 unchanged lines
```
−### Open systems shall be monitored for microbial activity, with the minimum monitoring being dip-slide testing at each service visit for total aerobic bacteria (TAB) and action levels defined in the Water Management Plan.
−
−### Routine Legionella sampling (culture method per ISO 11731 or qPCR molecular method) shall be performed at intervals specified in the Water Management Plan, with the typical interval being quarterly for non-healthcare facilities and monthly for healthcare and high-risk facilities.
−
### The local public health authority may require more frequent Legionella sampling.
…6 unchanged lines
### Treatment data — conductivity, ORP, pH, make-up flow, bleed flow, side-stream filter differential pressure, chemical-day-tank levels, alarm states — supports operation and recordkeeping when reported to the building automation system. {note}
+### Treatment data shall be reported to the building automation system through the controller's communication port, with the points listed below provided as a minimum, and point configuration coordinated with [[sync/building-automation-system]].
+
```datasheet
label: BAS Points from Water Treatment Controllers
…13 unchanged lines
```
−### Treatment data shall be reported to the building automation system through the controller's communication port, with the points listed below provided as a minimum, and point configuration coordinated with [[sync/building-automation-system]].
−
# Service Contract {toc}
…2 unchanged lines
### Each service visit produces the deliverables in the datasheet below. {note}
+### The water treatment service contract shall provide for routine on-site service at the frequencies established above.
+
+### Each service visit shall include a visual inspection of system conditions (sight glasses, sample-port samples, cooling tower basin condition, side-stream filter condition); a calibration check of conductivity, ORP, and pH probes; collection of water samples and field testing for the required parameters; calibration check and dose adjustment of chemical feed pumps; visual inspection of corrosion coupons in-place; microbiological testing per the program; review of the controller's data log for any trend indicating an issue; and a written service report uploaded to the Owner's records, the service provider's records, and the BAS as a service log point.
+
```datasheet
label: Routine Service Visit Deliverable
…10 unchanged lines
```
−### The water treatment service contract shall provide for routine on-site service at the frequencies established above.
−
−### Each service visit shall include a visual inspection of system conditions (sight glasses, sample-port samples, cooling tower basin condition, side-stream filter condition); a calibration check of conductivity, ORP, and pH probes; collection of water samples and field testing for the required parameters; calibration check and dose adjustment of chemical feed pumps; visual inspection of corrosion coupons in-place; microbiological testing per the program; review of the controller's data log for any trend indicating an issue; and a written service report uploaded to the Owner's records, the service provider's records, and the BAS as a service log point.
−
## After-Hours Response {toc}
### The standard commitment is on-site response within 4 hours during the cooling season and within 24 hours otherwise; healthcare facilities and other high-risk facilities require shorter response intervals. {note}
+### The service contract shall include a defined after-hours response commitment for emergency situations — significant chemistry excursion, suspected biological event, chemical spill, feed equipment failure during cooling-season operation.
+
```datasheet
label: After-Hours Response Commitment
…6 unchanged lines
```
−### The service contract shall include a defined after-hours response commitment for emergency situations — significant chemistry excursion, suspected biological event, chemical spill, feed equipment failure during cooling-season operation.
−
## Annual Comprehensive Review {toc}
…86 unchanged lines
### Lay-up methods are wet (system kept full of treated water with inhibitor concentration boosted, typically with slow or periodic recirculation, ideally with nitrogen blanketing where practical) and dry (system drained, blown dry with compressed air, sealed against air ingress, sometimes with desiccant cartridges in the equipment). {note}
+### Systems that are taken out of service for a season shall be laid up in a manner that protects the metal surfaces during the off-season.
+
```datasheet
label: Seasonal Lay-Up Method — Cooling Tower (Cold-Climate Winter)
…17 unchanged lines
```
−### Systems that are taken out of service for a season shall be laid up in a manner that protects the metal surfaces during the off-season.
−
### Wet lay-up is generally preferred for closed systems because the protective inhibitor film is maintained; dry lay-up is generally preferred for outdoor cooling towers in freezing climates and for any system where there is significant risk of freeze damage. {note}
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## The chemical-feed controllers and the BAS integration described here interface with the building automation system per [[sync/building-automation-system]], with the controller's communication protocol, point list, alarm priority, and trend logging configuration agreed at the BAS submittal stage.