Hi,

I have a home built in the 50's ant the heating system is original - tankless heater system, and the expansion tank is of the old style hanging from above.

Recently, I am experiencing constant dripping from the pressure release tubing once the water pressure goes above 20lbs. A tag says that the reducing valve was initially set at 12-15...however I don't remember if the pressure was reading 12-15 prior to this problem I'm having.

Having listened to the suggestion that when trying to drain the expansion tank, a "vacuum" might be occuring, I shut off the water supply and drained the system, of course resulting in 0 pressure...after a couple of days, the pressure had again elevated to above 20lbs...and, yes, the constant dripping again. Temporarily, I'm releasing water from the expansion tank to lower the pressure, and naturally the problem keeps occurring as I am trying to find out what the solution may be.

Is there any test I should perform to determine if the reducing valve is not doing its job? Any other possibilities I may not be considering?

It is my understanding (and as the tag reads) that the release valve should relieve after 30 lbs...but it just above 20 when this happens. It's been said that this valve is probably weak, but it seems that replacing this won't, of course, cure the problem of the pressure rising to over 20 constantly.

I am appreciative of any help you might be able to provide.

Thanks so much.