This WABCO 3CDC Type Air Compressors is equipped with an integral aftercooler that reduces the temperature of the compressed air to near ambient temperatures. Aftercoolers equipped with a bypass pipe (as seen here) provide additional protection during cold temperature operation. The high pressure discharge header has a built-in orifice that interfaces with the aftercooler bypass pipe. In the event of a restriction in the aftercooler caused by frozen condensate, the high pressure discharge is directed through the orifice to the aftercooler discharge and into the pipe connection to the No. 1 main reservoir.