The first step in “treating” compressed air is to reduce the discharge air temperature by utilizing an air-cooled aftercooler. Cooling the air to within 15-degrees of ambient temperature will cause up to 65% of the moisture to condense and “fall” out of the compressed air. It then would be trapped and removed with an auto drain. Aftercoolers are optional components on Reciprocating Air Compressors. Rotary Screw Air Compressors are typically factory equipped with an aftercooler.