Airmaxxx Pewter 400 Air Compressor 3 Gallon Air Tank Drain 120 on 150 off Switch. Airmaxxx Pewter 400 Air Compressor 3 Gallon Steel Air Tank Drain Valve 120psi on 150psi off Pressure Switch & Relay. Airmaxxx Pewter 400 Air Compressor 3 Gallon Steel Air Tank Drain Valve 120psi on 150psi off Pressure Switch & Relay.