Boiler pressure release leaking at 0 psi; spewing with tank fill (and psi & temp went high)

Thf

Hot water radiator boiler with extol tank under air scoop under brass pressure release valve. Last couple days, heat running 0 psi and 160 temp with water gurgling from release valve cap. when over gallon in bucket, I lifted the fill lever on the "bell" and it filled with water stopping on own at some point around 12-15 psi. I turned on heat - it ran up to 20 psi and nearly 220 temp, so I turned it off. Brass release valve spewing water. Plumber thought it was tank until I said temp went high- so now thinks something else bit what. He come slater to look , but seems still should be some concern about tank. Thoughts?

Jamie Hall

If the pressure went up like that, you have an expansion tank problem. But... if the temperature went up like that, you also have an aquastat problem.

Better you should get them both fixed -- and I like to replace the PRV when it has been activated like that.

JUGHNE

Is there water flow thru the boiler? Could any valves gotten shut off, possibly isolating the tank from the system?

Thf

Yes I think water flow through boiler - upstairs radiators were nice and hot (unlike past few days) - I bled them after I filled tank and before turning heat back on). I didn't touch anything but water fill lever and brass release cap (and of course thermostat)

Thf

Also- if that much water had leaked out and psi at 0 shouldnt water auto fill have kicked on on own? Or not - because of tank problem...? (Sorry- I'm just a homeowner with no expertise At all.)

Jamie Hall

The water fill did kick in on its own. However, if the expansion tank is full of water -- not air -- when the burner kicked on the water heated up and expanded and pop went the release valve. The auto fill won't let water out again -- just in. Just saw another one like that this morning.

Thf

Thanks for your help- Makes me more comfortable meeting the plumber later. I thought he mentioned maybe replacing the air scoop when he called - maybe he said aquastat...