How much water does an air compressor produce?

A 100 CFM compressor in warm, humid air can drop out 15–20 gallons of condensate per eight-hour shift; hot humid days produce far more than cool dry days.

Where does the condensate come out?

Most of it separates at the after-cooler and wet receiver, with the balance appearing at the dryer, filters and low points in the piping.

Can compressor condensate go down the drain?

Not untreated from a lubricated compressor. It carries oil and normally must pass through an oil/water separator to meet local discharge limits.

Condensate Load Calculator

All calculators

Formula

gal/day ≈ ṁ_air × (W_in − W_out) where W = 0.622·Pw / (Ptot − Pw)

Estimates water removed from compressed air by the aftercooler + dryer. Use to size auto drains, oil-water separators, and discharge piping.

Compressor delivery

scfm

Inlet air temperature

°F

Inlet relative humidity

Line pressure

psig

Dryer pressure dewpoint

°F

Hours run per day

Condensate produced

18.4gal / day

1.84 gal/hr · inlet dewpoint 74°F

Where the water goes

Aftercooler removes ~60–70% (drains at separator).
Refrigerated dryer removes most of the rest (drain on dryer).
Drip legs and filter bowls catch the remainder.
Oil-lubricated compressors: ALL of this water is contaminated — treat before disposal.

How to use this calculator

Predict how many gallons of water a compressor drops out per shift from ambient humidity.

Enter compressor flow in CFM and run hours.
Enter ambient temperature and relative humidity.
Enter discharge pressure and the after-cooler or dryer outlet temperature.
Read the expected condensate volume so drains and oil/water separators can be sized.

Frequently asked questions

How much water does an air compressor produce?: A 100 CFM compressor in warm, humid air can drop out 15–20 gallons of condensate per eight-hour shift; hot humid days produce far more than cool dry days.
Where does the condensate come out?: Most of it separates at the after-cooler and wet receiver, with the balance appearing at the dryer, filters and low points in the piping.
Can compressor condensate go down the drain?: Not untreated from a lubricated compressor. It carries oil and normally must pass through an oil/water separator to meet local discharge limits.