Question If using air tanks with manually operated drains, how often should you drain the tanks? Answers Every day Once a week Once a month Once every six months Explanation In an air brake system with manually operated drains, the tanks should be drained at the end of each day of driving. This questions appears in the following tests: Arkansas Air Brakes District Of Columbia Air Brakes Indiana Class B Knowledge Test Massachusetts Air Brakes Mississippi Air Brakes South Carolina Class A Knowledge Test South Dakota Air Brakes Tennessee Class A Knowledge Test Wyoming Air Brakes