Question What is removed when an air tank is drained? Answers Water and oil Ammonia Liquid cleaners Explanation In an air brake system, air tanks have drains to remove accumulations of water and compressor oil. Allowing water and oil to accumulate in the system could cause damage to the brakes. Take a FREE Practice Test Now This questions appears in the following tests: Virginia Knowledge Test Class A , Alabama Knowledge Test Class B , Ohio Knowledge Test Class B , Tennessee Passenger , Idaho Air Brakes , Iowa Air Brakes , Louisiana Air Brakes , New Hampshire Air Brakes , Vermont Air Brakes ,