The Bell & Gossett tank purge valve (TPV) is a combination full port ball type isolation valve and drain valve used to connect the system to the expansion tank. This valve allows the tank to be drained for easy servicing or tank replacement without having to drain the system. Available in various NPT/sweat connections from 1/2, 3/4, 1, 1-1/4, 1-1/2 and 2 in sizes, these valves are furnished standard with a drain valve with a 5/8 in hose connection. These valves can be used on all series ''B'' and ''D'' tanks and are not recommended to be used on potable water tanks.