Higher cooling-tower makeup water can reflect heavier cooling demand, increased blowdown, drift, leaks or basin overflow. Compare makeup and blowdown readings over the same period, then review load, weather, conductivity and control records. Have the tower and water-treatment specialists correct the cause while maintaining the building’s Legionella controls.
What readings should be compared?
Investigate a change in tower water use before adjusting the equipment.
Extra makeup water does not automatically mean a buried plumbing leak. A cooling tower loses water through normal evaporation, controlled blowdown and drift, the small droplets carried out with the air. Unwanted leaks or basin overflow can add another loss. Identify which part changed before adjusting anything.
EPA's October 2012 WaterSense at Work guidance explains this water balance. It is engineering guidance, not a current Phoenix permit rule or a guaranteed savings estimate for your building.
Use makeup and blowdown meter readings covering the same dates and operating period. Makeup is the replacement water entering the system. Blowdown is water deliberately discharged to control the dissolved solids that remain as water evaporates.
First confirm what each meter serves. A whole-building utility meter cannot isolate tower use if it also includes restrooms, irrigation or other equipment. The commercial submeter guide explains that boundary check.
Collect a small investigation record:
| Record | What it helps explain |
|---|---|
| Makeup and blowdown totals | Whether incoming water and controlled discharge changed together |
| Cooling load, run hours and weather | Whether the tower had more heat to reject |
| Conductivity and treatment records | Whether water-quality control changed the discharge requirement |
| Controller settings, alarms and work dates | Whether a fault or service change preceded the increase |
| Basin level and overflow observations | Whether replacement water is escaping without doing useful work |
Normalize comparisons for operating conditions. A hotter or busier period may legitimately require more evaporation. The overnight water-use investigation helps distinguish scheduled equipment demand from unexplained flow elsewhere in the building.
What can a technician check at the tower?
Have the tower technician examine the makeup valve, level controls, overflow path, leaks and blowdown control against the actual model's instructions. Avoid climbing into or reaching around operating equipment to investigate a meter reading.
For example, Baltimore Aircoil's Series 3000 manual describes inspection and leak checks for its mechanical makeup-valve arrangement. It also identifies optional electric level control and remote-sump arrangements. That is a reason to identify your actual setup, not to apply one model's valve adjustment or basin level to every tower.
If makeup rises while the documented cooling load is steady, investigate those controls and unintended losses. If blowdown also rises, have the water-treatment specialist examine conductivity measurement, source-water changes and the treatment program before deciding the discharge is excessive.
Why shouldn't I simply close the blowdown valve?
Blowdown controls concentration of dissolved solids. Closing it solely to reduce the meter reading can compromise the treatment program. CDC recommends automated blowdown for water quality and coordinated controls for scale, corrosion and disinfectant management.
There is no universal cycles-of-concentration setting that fits every source water, tower material and operating temperature. EPA and the manufacturer call for a qualified water-treatment provider. Keep the tower within the site's Legionella water-management program, with documented monitoring and corrective actions.
Meter capacity is another separate question. If equipment or building demand is changing, review the commercial water-meter sizing factors rather than treating a high water total as proof that the service is undersized.
After the cause is corrected, compare readings under similar operating conditions and retain the control and treatment records. Reduced water use is useful only while the tower still performs and its water-quality controls remain effective.