AirSprayTech Academy Certificate Program

Water and Wastewater Protective Coating Systems

Article 23 of 24

Cure, Disinfection, Commissioning, and Return to Service

Protecting the completed coating system during the critical transition from application to operation

Applied Does Not Mean Ready for Service

A coating system can be properly selected, mixed, applied, and inspected yet still fail if the structure is returned to service before the coating has developed the required cure. Premature filling or exposure can cause softening, swelling, blistering, discoloration, chemical attack, loss of adhesion, taste and odor complaints, or contamination of potable water.

Return to service must be treated as a controlled project phase. The coating must complete its specified cure, the structure must pass final inspection and testing, potable-water surfaces must be cleaned and disinfected as required, and the responsible authority must provide authorization before operation begins.

Understand the Different Stages of Cure

Product literature may use several cure-related terms. They must not be treated as interchangeable.

• Dry to touch: The surface can be lightly touched without material transferring. This does not mean the coating can be handled, recoated, immersed, or exposed to chemicals.
• Dry to handle: The coated item can tolerate limited handling without unacceptable damage.
• Recoat time: The period during which another coat may be applied under specified conditions.
• Full cure: The coating has developed the physical and chemical properties defined by the manufacturer.
• Immersion cure: The minimum cure required before continuous liquid exposure.
• Chemical-service cure: The cure required before exposure to specified chemicals, concentrations, temperatures, or cleaning procedures.
• Potable-water return-to-service cure: The cure and preparation required by the product listing, manufacturer, specification, facility, and regulatory authority before contact with drinking water.

A coating that is dry to the touch may still be chemically active, mechanically weak, or capable of releasing solvents and reaction byproducts.

Never Shorten Cure Time to Recover the Schedule

A delayed project schedule does not change the coating's chemical requirements. Filling a tank, wet well, clarifier, pipe, or process structure early transfers the schedule problem into the coating system and may create a much more expensive failure.

Any proposed accelerated-cure procedure must be approved in writing by the coating manufacturer and responsible project authority. Uncontrolled heating, direct flame, excessive temperature, or unapproved chemical additives must not be used.

Factors That Control Cure

Cure time is affected by more than the number of hours shown on a product data sheet. Consider:

• Air temperature during and after application.
• Substrate temperature and thermal mass.
• Relative humidity and moisture exposure.
• Ventilation rate and air exchange.
• Coating chemistry and reaction mechanism.
• Applied film thickness and areas of excessive buildup.
• Correct mix ratio and thoroughness of mixing.
• Induction time, component temperature, and material condition.
• Number of coats and time between coats.
• The intended service liquid, chemical concentration, temperature, and exposure duration.

Cure schedules are commonly based on a stated temperature. If the actual coating or substrate temperature falls below that value, cure may take substantially longer. Record actual conditions throughout the cure period.

Maintain Environmental Control During Cure

Environmental control should continue after spraying is complete. Turning off ventilation, heat, cooling, or dehumidification immediately after application may change the conditions required for cure.

• Maintain temperatures within the manufacturer's approved cure range.
• Prevent condensation from forming on the coating.
• Continue ventilation long enough to remove solvents, moisture, and reaction byproducts.
• Avoid directing excessive airflow onto uncured coating if it could cause uneven cure, contamination, or surface defects.
• Keep doors, hatches, and access openings controlled to prevent dust, insects, water, or unauthorized entry.
• Record temperatures, humidity, ventilation interruptions, and unusual events during the cure period.

Ventilation Must Not Create Another Hazard

Ventilation equipment, heaters, electrical devices, and temporary power must be suitable for the hazards present. Exhausted vapors must be discharged to an approved location where they will not enter occupied buildings, air intakes, ignition areas, or operating treatment processes.

Confined-space controls remain in effect whenever employees enter the structure for environmental readings, inspection, cleaning, repairs, or equipment removal. A completed coating application does not automatically eliminate atmospheric hazards.

Verify Cure Before Cleaning or Testing

Do not subject the coating to water, disinfectant, detergent, solvent, holiday testing, adhesion testing, foot traffic, ladders, or equipment installation until it has reached the cure required for that activity.

Cure verification may include:

• Documented elapsed time at acceptable temperatures.
• Visual and tactile examination.
• Manufacturer-approved hardness testing.
• Solvent-rub testing when appropriate for the coating chemistry.
• Shore hardness testing for specified elastomeric systems.
• Examination of retained cure samples or test panels.
• Product-specific analytical testing when required.

One cure test is not suitable for every chemistry. Follow the current manufacturer procedure and project specification for the actual product installed.

Complete Final Inspection Before Cleaning

Before cleaning, disinfection, or filling, confirm that:

• All specified coating layers have been applied.
• The system has reached the required cure.
• Visual defects have been repaired.
• Required thickness measurements are complete and acceptable.
• Holiday testing has been completed where required.
• Repairs have been cured and successfully retested.
• Temporary masking, abrasive, dust, tools, scaffolding, lighting, and application equipment have been removed.
• Piping, valves, mixers, aeration equipment, ladders, hatches, vents, overflows, screens, and seals are properly installed.
• The interior has been inspected for foreign material and physical damage.

Cleaning the Completed Structure

Final cleaning removes dust, debris, insects, footprints, loose particles, equipment residue, and other foreign material. The cleaning procedure must not damage the coating or leave incompatible residues.

• Use only manufacturer-approved cleaning methods and materials.
• Confirm that the coating has cured sufficiently for washing.
• Control water pressure, nozzle distance, temperature, and mechanical cleaning force.
• Avoid sharp tools, abrasive pads, or equipment that can cut or polish the coating.
• Remove cleaning water, debris, and residue completely.
• Inspect the coating again after cleaning and drying.

Cleaning water and residue must be collected, characterized, and disposed of according to project requirements and applicable environmental regulations. They must not be released into the treatment process without authorization.

Potable-Water Coatings and NSF/ANSI/CAN 61

NSF/ANSI/CAN 61 establishes health-effects criteria for materials, components, products, and systems that contact drinking water. A statement that a product is compliant or certified must be verified through the current listing and must apply to the exact product and intended use.

Confirm listing conditions such as:

• Exact product name and manufacturer.
• Approved primer, lining, topcoat, filler, and repair components.
• Colors or formulations included in the listing.
• Minimum tank, pipe, or exposure size limitations.
• Maximum surface-area-to-volume ratio.
• Maximum use temperature.
• Required film thickness and number of coats.
• Minimum cure time and temperature.
• Required rinse, flush, or conditioning procedure.

Certification does not mean that any application thickness, cure schedule, tank size, repair material, or service condition is automatically acceptable. The installation must remain within the current listing limitations.

Do Not Claim NSF Certification for an Unlisted System

A certified topcoat does not automatically make every primer, filler, surfacer, patching compound, reinforcement, thinner, or repair product beneath it acceptable for potable-water contact.

Verify the complete installed system against the current official listing. Product labels, older literature, distributor descriptions, and general marketing statements should not replace listing verification.

Disinfection of Potable-Water Storage Facilities

AWWA C652 addresses disinfection of water-storage facilities, including facility preparation, disinfectant application, sampling, coliform testing, chlorine residual, and acceptable aesthetic water quality. The project must use the edition required by the owner and regulatory authority.

Before disinfection:

• Confirm final coating cure and written inspection acceptance.
• Verify that disinfectant concentration and contact time will not damage the coating.
• Confirm the selected AWWA disinfection method with the owner.
• Inspect hatches, vents, overflows, screens, gaskets, seals, drains, and sanitary protection.
• Remove all foreign materials and complete the approved cleaning procedure.
• Establish procedures for handling, neutralizing, discharging, or disposing of chlorinated water.
• Coordinate sampling locations, laboratory requirements, and acceptance criteria.

Disinfectant Can Damage an Inadequately Cured Coating

High disinfectant concentration, extended contact time, elevated temperature, or application before complete cure may discolor, soften, oxidize, blister, or otherwise damage some coating systems.

Coordinate the coating manufacturer's limitations with the selected disinfection procedure. When requirements conflict, obtain written direction before proceeding.

Potable-Water Sampling and Acceptance

After disinfection, flushing, and filling, the facility may require bacteriological sampling, chlorine-residual measurements, turbidity evaluation, and confirmation of acceptable taste, odor, and appearance.

Sampling should be performed by qualified personnel using approved containers, locations, preservation methods, holding times, and laboratories. The applicable AWWA standard, owner procedure, and public-health authority determine the number of samples, timing, test parameters, and acceptance criteria.

The contractor should not represent a potable-water facility as ready for service merely because it has been filled. Required laboratory results and authorization must be received before the facility is connected to the active system.

Wastewater Structures Require a Different Startup Plan

Wastewater structures generally are not disinfected for drinking-water service, but they still require controlled commissioning. The new lining may be exposed to sewage, industrial waste, hydrogen sulfide, sulfuric acid, treatment chemicals, grit, turbulence, cleaning equipment, and biological activity.

Before startup:

• Verify full immersion and chemical-service cure.
• Confirm that all cleaning water, debris, solvents, and construction residue have been removed.
• Inspect joints, penetrations, terminations, supports, mixers, aeration equipment, and mechanical attachments.
• Confirm that startup chemicals and concentrations are compatible with the lining.
• Coordinate bypass removal, valve operation, flow introduction, and process startup with facility operations.
• Protect the coating from dropped tools, dragging hoses, sharp equipment, and uncontrolled maintenance traffic.
• Establish a plan for observing the system during initial operation.

Controlled Filling and Initial Exposure

Filling should follow the facility's written commissioning procedure. Rapid filling, uneven liquid loading, uncontrolled flow, or thermal shock may create stresses that were not present during coating application.

• Confirm all drains, valves, penetrations, hatches, and temporary openings are properly configured.
• Introduce water or process liquid at the approved rate and location.
• Avoid concentrated flow directly against uncured repairs or vulnerable details.
• Monitor for leakage, abnormal odor, discoloration, floating debris, foam, or coating distress.
• Record fill level, time, temperature, process conditions, and observations.
• Stop filling and investigate if abnormal conditions appear.

The coating contractor should not independently operate facility process equipment unless that responsibility is specifically assigned and the personnel are authorized and qualified.

Remove Temporary Equipment Without Damaging the Work

Scaffolding, platforms, ventilation ducts, lighting, hoses, cables, ladders, masking, and containment materials must be removed carefully. Many final coating defects occur after inspection because temporary equipment is dragged, dropped, or dismantled against the finished lining.

• Use protective pads at contact points.
• Lift equipment rather than dragging it across coated surfaces.
• Control sharp edges, fasteners, wire, and scaffold components.
• Inspect support and anchor locations after equipment removal.
• Repair and retest all resulting damage before cleaning and service.

Pre-Commissioning Walkdown

The contractor, owner, inspector, engineer, facility operator, and manufacturer representative should participate when required. The walkdown should confirm:

• All coating work and repairs are complete.
• Inspection and testing records are acceptable.
• The required cure period has been completed under acceptable conditions.
• The structure is clean and free of tools, debris, temporary materials, and standing water.
• All mechanical equipment and sanitary components are installed correctly.
• Punch-list items affecting service have been closed.
• Cleaning, disinfection, flushing, sampling, and filling procedures are approved.
• Emergency contacts and stop-work authority are established.

Written Authorization Is the Release Point

Verbal statements such as “it should be ready,” “the coating feels hard,” or “we need the tank tonight” are not adequate authorization for return to service.

The responsible owner or project authority should issue written authorization after the required cure, inspection, repairs, cleaning, testing, disinfection, sampling, and documentation have been accepted.

Stop the Return-to-Service Process When

• The required cure time or temperature history cannot be verified.
• The coating remains soft, tacky, odorous, discolored, or otherwise abnormal.
• Required inspection, holiday testing, thickness testing, or repairs are incomplete.
• Cleaning or disinfection procedures conflict with manufacturer limitations.
• Potable-water listing conditions cannot be verified.
• Bacteriological or water-quality results do not satisfy acceptance requirements.
• Debris, contamination, standing water, leaks, or physical damage are present.
• Required regulatory or owner authorization has not been received.
• Abnormal conditions appear during filling or startup.

Return-to-Service Documentation

The commissioning record should include:

• Date and time of final coating application.
• Cure-period air and substrate temperature records.
• Ventilation, heating, cooling, and dehumidification records.
• Cure-verification results.
• Final inspection, thickness, holiday, adhesion, and repair records.
• Current potable-water product listings when applicable.
• Cleaning and disinfection procedures and completion records.
• Disinfectant concentration, contact time, flushing, and disposal records.
• Bacteriological and water-quality laboratory reports.
• Pre-commissioning walkdown and punch-list closure.
• Filling, startup, and initial-observation records.
• Written authorization for return to service.

Contractor's Field Standard

Do not release a coated structure because application is finished. Release it only after the specified cure has been documented, inspection and repairs are complete, required cleaning and disinfection have been performed, acceptance results have been received, and the responsible authority has issued written authorization.

Knowledge Check

1. Why does dry-to-touch not mean that a coating is ready for immersion?
2. What conditions should be recorded throughout the cure period?
3. Why must the exact conditions of an NSF/ANSI/CAN 61 listing be verified?
4. Why must disinfection procedures be coordinated with the coating manufacturer?
5. How does commissioning a wastewater structure differ from returning a potable-water tank to service?
6. What conditions should stop the return-to-service process?
7. Who should provide the final written authorization for service?

Technical References

• ANSI/AWWA C652-25: Disinfection of Water-Storage Facilities.
• ANSI/AWWA C651: Disinfecting Water Mains, when the coating project includes affected water mains or connecting piping.
• NSF/ANSI/CAN 61: Drinking Water System Components—Health Effects.
• NSF Official Listings: Current certification conditions for products and systems used in drinking-water contact.
• U.S. Environmental Protection Agency: Finished Water Storage Facility Inspection and Cleaning resources and applicable drinking-water requirements.
• OSHA 29 CFR 1910.146: Permit-Required Confined Spaces.
• OSHA 29 CFR 1910.1200: Hazard Communication.
• Manufacturer requirements: Current product data sheets, safety data sheets, cure schedules, potable-water listing limitations, chemical-resistance data, cleaning instructions, and written return-to-service procedures.

Standards, certifications, listings, and regulations may change. Confirm the current edition and applicable federal, state, local, owner, and public-health requirements before developing a cleaning, disinfection, commissioning, or return-to-service procedure.

Professional responsibility: The coating contractor should not independently change cure periods, disinfection concentrations, cleaning procedures, filling schedules, or return-to-service requirements. Conflicting requirements must be resolved in writing by the responsible manufacturer, engineer, owner, or regulatory authority before proceeding.

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