I have a hot water radiator system. Closed system with the diaphram expansion tank. The tank is filled with water and causing system pressure problems. I’ve read that I should drain the water from the expansion tank, but I can’t find anything that looks like a drain valve. There is only one valve on the tank, and it is on the bottom of the tank, and it is like a bicycle tire air valve. What do I do ?
First depress the pin in the air valve to see if air or water comes out. If it is water, then the tank is bad and has to be replaced. If it is air or nothing comes out, you should remove the tank from the system and they either release air or pump some in until the pressure in the tank is about 10#. You cannot do it with the tank in the system unless you drain all the pressure out of the boilet. And even they you may not pressurize it properly since all the water may not leave the tank before you add air.