What is an ASHRAE 188 water management program?
A water management program under ASHRAE Standard 188 is a written plan to control the conditions that let Legionella grow and spread. It names a program team, describes the water systems, finds where hazardous conditions can occur, sets control limits at those points, and defines the monitoring, corrective actions and records. The program is reviewed at least once a year.
A complete program covers:
- the program team and who decides what;
- a description of each water system, with flow diagrams;
- a hazard analysis of where water stagnates, warms or sprays;
- control locations, each with a control limit;
- monitoring at each control location;
- corrective actions for each limit that is missed;
- confirmation that the program is followed and that it works;
- documentation and communication.
Many plants treat their towers with a chemical program and a service schedule but have no written hazard analysis, control limits or response plan, which are the parts ASHRAE 188 asks for.
Which plant systems need one?
- Cooling towers and evaporative condensers. ASHRAE 188 calls for a program wherever these are present.
- Process water that is warm, recirculated or sprayed, such as extrusion cooling tanks, quench tanks and wash water. It carries the same risk and belongs in the hazard analysis.
- Humidifiers, misters and decorative water features.
- Hot and cold domestic water in larger buildings on the site.
Some states and cities, New York among them, also require cooling-tower registration, a maintenance plan and routine Legionella sampling. Check the rules where each tower sits.
Where UV-C fits in a water management program
UV-C is a physical control at a defined point. Water that passes through the lamp field is treated. Cognituv puts in-line UV-C on the recirculating loop or a side-stream, or submersible UV-C in the basin or tank.
- It works alongside the chemical program. It can reduce how much biocide the program needs to hold its control limits. The program team decides that from the data.
- It treats the water that passes the lamps. Biofilm already established in fill, basins and piping still needs cleaning. Read more on biofilm and where UV-C fits.
- It can be written into the program as a control location, with lamp output as the monitored parameter, a control limit and a corrective action, like any other control.
See UV-C for cooling towers for the hardware.
What to monitor between Legionella tests
| Parameter | Why it matters | Cognituv Connect sensor |
|---|---|---|
| Free chlorine or oxidation-reduction potential (ORP) | Shows whether biocide residual is holding | Water-quality sensor, pH, ORP and temperature sensor |
| pH | Biocide performance and corrosion | Water-quality sensor |
| Conductivity | Cycles of concentration and blowdown | Conductivity sensor |
| Turbidity | Solids that shelter microbes | Turbidity sensor |
| Water temperature | Time spent in the growth range | Water-quality sensor |
| Flow and level | Stagnation and low turnover | Water flow meter, level sensors |
| UV-C lamp output | Confirms the UV control point is working | UV-C irradiance sensor |
Sensors don’t detect Legionella. Culture sampling, at the frequency your program and your jurisdiction set, remains the validation step. Continuous readings show whether control limits held in the weeks between samples, and they flag a problem before the next lab result comes back.
How to add a monitored UV-C control point
- Confirm the control location in the hazard analysis: make-up water, recirculating loop, side-stream, or basin.
- Record a baseline of water quality and current chemistry for at least two weeks.
- Size the UV-C to the recirculation or side-stream flow, or place submersible UV-C in the basin or tank.
- Add lamp output, flow and water-quality readings to Cognituv Connect, each with its control limit.
- Write the corrective action for each limit into the program.
- Review at 30, 60 and 90 days, then at the annual program review.
Frequently asked questions
Does UV-C replace biocide in a cooling tower?
No. UV-C is a supplemental control that works alongside the chemical program. With the data in hand, the program team may decide the site can hold its control limits with less biocide.
Can sensors detect Legionella?
No. Water-quality sensors track the conditions that let Legionella grow, such as residual, pH, temperature and flow. Culture sampling confirms whether the program works.
Does UV-C treat the whole tower?
It treats the water that passes through the lamp field. How much of the loop that covers depends on flow and turnover, which is why sizing starts from the recirculation rate.
Who should be on the water management program team?
Typically facilities or plant engineering, the EHS team, the water treatment provider, and anyone who can authorize corrective actions. Healthcare sites add infection prevention.
How often should a cooling tower be tested for Legionella?
At the frequency your program and your jurisdiction set. Some jurisdictions fix the interval in their code. Continuous monitoring doesn’t replace that testing.
Codes and standards are listed for reference. A listing isn’t a compliance finding for your facility, and doesn’t mean any product, Cognituv’s included, is certified to it. Performance depends on installation, flow, water chemistry and maintenance; results are verified by measurement, not assumed. Updated November 5, 2026.