Formula & worked example
E≈0.00153·Q·ΔT(°C); D=Q·drift%; B=max(0,E/(COC−1)−D); M=E+D+B.
1,000 m³/h cooled by 10°C at 4 cycles gives about 15.3 m³/h evaporation before drift and blowdown.
HVAC & plant engineering calculator · Updated Sep 17, 2026
Cooling Tower Water Balance Calculator — Evaporation, Drift, Blowdown & Makeup
Calculate cooling-tower range, heat rejection, evaporation, drift, blowdown, makeup water and annual water use from circulation, temperatures and cycles of concentration.
Inputs
Live engineering result
Cooling range 10 °C
Approx. heat rejection 11,627.778 kW
Evaporation 15.3 m³/h
Drift 0.02 m³/h
Required blowdown 5.08 m³/h
Makeup water 20.4 m³/h
Annual makeup 122,400 m³/year
Assumptions & limits
- Evaporation uses a common approximate water-balance factor; climate and tower performance change actual evaporation.
- Drift participates in dissolved-solids removal, so it is subtracted from required blowdown.
Frequently asked questions
What does this Cooling Tower Water Balance Calculator calculate?
Calculate cooling-tower range, heat rejection, evaporation, drift, blowdown, makeup water and annual water use from circulation, temperatures and cycles of concentration.
Can I use this for final design?
Use it as an auditable engineering sizing cross-check. Final equipment and piping selections should use project design conditions, manufacturer data, applicable standards and local code.
Why are the engineering assumptions shown?
Plant calculations are sensitive to fluid properties, pressure, temperature and operating hours. Exposing assumptions makes the result easier to verify instead of hiding them behind a single answer.