David Lee
If you mean the pressure relief valve, and if it is a bladder type expansion tank, then the air charge could be too high to allow the expansion tank to operate and therefore the expansion is being relieved as a high pressure situation. The ideal charge is about 1/2 the systems operating pressure. : The backflow preventer on my hot water central heating system is dripping very slightly after an new expansion tank has been installed. The heating system does not have isolation valves and replacing the preventer is a big job.Is the dripping serious? What is the best way to fix it? Could I leave it alone?
