Use this handy check valve system to prevent back flow of water thru airline into rotary vane compressors. It installs into the air inlet of the air compressor and the air filter connects to it as shown in the alternate image.
Item #RVC is sized for the 1/4 HP RV33, and item #RVC2 is sized for the 3/4 & 1 HP RV75 & RV100.