Cooling Tower Makeup Water Calculator
Estimate cooling tower makeup water: evaporation, blowdown, drift and total consumption from range, flow and cycles of concentration.
Inputs
Difference between hot return and cold supply.
Higher COC saves water but requires better treatment.
Modern drift eliminators: 0.001–0.02% of recirc.
Results
Formula
Makeup = 0.001·Q·ΔT + Q·drift% + Evap/(COC−1).
Worked example
A 1,000 GPM tower with 10°F range at 4 cycles: Evaporation ≈ 10 GPM, blowdown ≈ 3.3 GPM, drift ≈ 0.2 GPM, total ≈ 13.5 GPM. At 6,000 hrs/yr that's 4.86 million gallons.
Related calculators
Frequently asked questions
What is 'cycles of concentration'?
The ratio of TDS in blowdown to TDS in makeup. Higher COC means less blowdown but more concentrated water — needs stronger chemical treatment.
Can COC be increased indefinitely?
No — LSI, silica and calcium hardness limit COC. Most towers run 3–7.
Does this include chemical bleed?
No — deliberate chemical bleed is normally counted inside blowdown. Add extra makeup if you dose separately.
One short email a month. Free PDFs, worked examples, no spam.