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It was the third week of August. The plant engineer had walked past the cooling tower twice that day without stopping. The fans were spinning, the basin looked clear, and nothing seemed alarming enough to slow him down.
Nobody had pulled a water sample in six weeks.
Here’s what was happening inside that tower while he walked past. August evaporation rates are the highest of the year. Water leaves the system faster in peak heat than at any other point in the operating season — and when water evaporates, the dissolved minerals it was carrying stay behind. They concentrate in the basin. Quietly, continuously, and without any visible sign.
The system was drifting. By the time production called about a heat complaint in week four, the drift had been accumulating for weeks.
A free ChemREADY water analysis tells you your exact conductivity, cycles of concentration, and inhibitor residuals right now — before the next utility bill does.
Schedule your free water analysis →Cycles of concentration (CoC) is the ratio of dissolved solids in a cooling tower’s recirculating water to dissolved solids in the fresh makeup water entering the system. It measures how many times the mineral content of the recirculating water has multiplied compared to the incoming supply. Most industrial cooling tower programs target a CoC range of 3 to 6, depending on local water quality and system design.
When cycles drift above the program’s target range, the water is holding more dissolved minerals — calcium, magnesium, silica, sulfate — than the cooling tower chemical program was designed to manage. At that point, the water starts depositing what it can no longer hold in solution: scale on heat exchange surfaces, fill media, and equipment components.
Conductivity is the practical measurement of CoC in real time. Conductivity (measured in µS/cm or µmho/cm) reflects the electrical conductance of dissolved ions in the water — the more dissolved solids, the higher the conductivity reading. When conductivity climbs, cycles are climbing with it. Most programs set a conductivity target and use blowdown — the controlled discharge of basin water, often managed by a conductivity controller — to maintain it.
The short answer is evaporation. But the mechanism is worth understanding, because it’s what makes August specifically the highest-risk period in the operating year.
In peak heat, a cooling tower’s evaporation rate — the fraction of recirculating water that evaporates rather than flowing through the system — increases significantly. On a hot August day, a 500-ton cooling tower may evaporate 15–20% more water than on a mild spring day. When that additional water evaporates, it leaves all of its dissolved minerals behind.
If blowdown — the automatic or manual discharge of concentrated basin water to bring in fresh makeup — doesn’t increase proportionally to account for higher evaporation rates, the minerals accumulate faster than the program can flush them. Conductivity climbs. CoC rises above target.
Most cooling tower control programs set a fixed conductivity setpoint in spring and don’t revisit it through summer. That setpoint was calibrated for a different evaporation rate. By August, it’s likely no longer keeping pace with what the system is actually doing.
When conductivity exceeds program targets, several failure modes develop simultaneously — most of which are invisible until they’ve been compounding for weeks:
Each of these has its own countermeasure — a properly balanced corrosion and scale inhibitor program, an active biocide program to hold biological growth in check, and side stream filtration to pull suspended solids before they foul the fill. But none of them work if no one knows the conductivity has drifted in the first place.
The honest answer is: more often than most facilities are currently testing. The right frequency depends on system size, water quality, and evaporation rate — but here’s a practical baseline for peak-season tower management:
Digital remote monitoring makes this cadence automatic. Conductivity, pH, and inhibitor residuals are tracked continuously, with alerts when parameters drift outside setpoints. That’s the difference between catching drift in hours and discovering it in week four when production calls.
This is the question most facilities haven’t explicitly asked — but it’s the one that determines whether their tower is actually protected in August.
A chemical delivery is a scheduled drop-off of treatment chemicals. Someone fills the drum, checks the system is running, and leaves. The chemical concentration in the water adjusts based on dosing equipment that was calibrated in spring. Nobody is actively checking whether that dosing rate is appropriate for what August evaporation is doing to the system.
A cooling tower water treatment program is an active managed system. A program means someone is regularly testing the water, reviewing the results against program targets, adjusting blowdown rates and chemical feed as conditions change, documenting the data, and identifying drift before it becomes damage.
The system was corrected. A water test showed conductivity at nearly double the program’s target range. Calcium carbonate deposits on the condenser surfaces were treated. Blowdown was recalibrated for peak-season evaporation rates. The corrosion and scale inhibitor program was rebalanced for the actual mineral load in the water.
The tower came back to spec. But the facility absorbed weeks of elevated energy costs and reduced heat rejection capacity during the hottest period of the year. That’s the cost of a walkby.
This pattern — conductivity drift in August, discovered only when something downstream complains — is one of the most common findings when ChemREADY technicians walk a cooling tower that hasn’t had active management through summer. It’s not dramatic. The tower keeps running. The damage accumulates slowly, invisibly, in the deposits on your heat exchanger and the line items on your utility bill.
ChemREADY's cooling tower water treatment program includes active summer monitoring and blowdown management — not just chemical drop-offs. The difference is what happens between deliveries.
See cooling tower services →A free water analysis gives you your exact conductivity, cycles of concentration, inhibitor residuals, and biological indicators — before the next utility bill does.
Schedule your free water analysis →Or call us directly: 800-229-6801
Active monitoring, blowdown management, and inhibitor programs built around your system — not a chemical drop-off.
See cooling tower services →Continuous conductivity, pH, and inhibitor tracking with drift alerts — so you catch summer drift in hours, not weeks.
Explore remote monitoring →The right inhibitor balance for your actual mineral load — the program that keeps drift from turning into deposits.
See inhibitor programs →