To Drain or not to Drain?
Air reservoirs serve as storage tanks for compressed air. They collect water condensed from the air, and small amounts of oil normally enter the reservoir in the form of vapor, because of the heat generated during the compression. After the water and oil condense, they collect near the tank drain valves and should be drained regularly.
If the air tanks are not equipped with automatic drain valves, you should drain the tanks daily during vehicle operation.
If they are equipped with automatic drain valves, they should still be drained manually every six months during operation. To drain the tanks, pull the three drain lanyards provided until all moisture is expelled.