How do you calculate cooling tower evaporation rate?

Evaporation rate (GPM) is calculated as: Recirculation Rate (GPM) x Temperature Differential (°F) x 0.001. For example, a system recirculating 1,000 GPM with a 10°F temperature drop evaporates approximately 10 GPM. This formula uses the rule of thumb that about 1% of recirculation water evaporates per 10°F of cooling.

What are typical cycles of concentration for cooling towers?

Typical cycles of concentration (CoC) range from 3 to 6 for most cooling towers. Higher cycles mean less blowdown water waste but increase scaling and corrosion risk. The optimal CoC depends on makeup water quality, treatment chemistry, and local discharge regulations. Systems using softened or RO-treated makeup water can often achieve 6-10 cycles.

How do you calculate cooling tower makeup water requirements?

Makeup water = Evaporation + Blowdown + Drift losses. Blowdown is calculated as Evaporation / (Cycles of Concentration - 1). Drift is typically 0.001% to 0.005% of recirculation rate for modern towers. Total makeup water is the sum of these three components and represents the fresh water that must be supplied to the tower.

Cooling Tower Evaporation & Makeup Water Calculator

Cooling Tower Evaporation & Makeup Water Calculator | ForeverPure

Cooling Tower Evaporation & Makeup Water Calculator

Calculate evaporation rate, blowdown, makeup water requirements, and annual water & chemical costs for cooling tower systems.

Tower Operating Parameters

Recirculation Rate

GPM

Temperature Differential (ΔT)

Temperature drop across the tower (hot water in minus cold water out)

Cycles of Concentration (CoC)

cycles

Typical: 3–6 for untreated makeup; 6–10 for softened/RO water

Drift Loss

% of recirc

Modern towers: 0.001–0.005%; older towers: up to 0.02%

Operating Hours per Day

hrs/day

Water Balance Results

Evaporation Rate

Blowdown Rate

Drift Loss

Total Makeup Water

Daily Makeup Volume

Annual Water Consumption

Formulas Used

Evaporation (GPM) = Recirculation Rate × ΔT(°F) × 0.001 Blowdown (GPM) = Evaporation / (Cycles of Concentration − 1) Drift (GPM) = Recirculation Rate × Drift% / 100 Makeup (GPM) = Evaporation + Blowdown + Drift

Water & Chemical Cost Estimate

Water Cost

$ / 1,000 gal

Sewer / Discharge Cost

$ / 1,000 gal

Applied to blowdown volume only

Chemical Treatment Cost

$ / 1,000 gal makeup

Annual Cost Estimate (365 days)

Annual Water Cost

Annual Sewer Cost

Annual Chemical Cost

Total Annual Cost

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