The BURCAM 600545B 21 US gal vertical captive air pressure tank is designed for residential water systems assembled with a jet pump or a deep well submersible pump. The tank has a tough, epoxy-baked steel finish and stainless steel flange with a 1” NPT connection. The replaceable bladder is made of synthetic butyl rubber to increase reliability and life span. There is no water to metal contact for rust-free operation. The maximum working pressure is 100 PSI. The tank comes factory precharged at 28 PSI. For use with a 20/40 PSI pressure switch, the air pressure in the empty tank must be adjusted to 18 PSI; for a 30/50 PSI switch, the pressure must be adjusted to 28 PSI. The drawdown is 7.5 US gal for a 20/40 PSI switch setting and 6.0 US gal for a 30/50 PSI switch setting.