I’m a carpenter, but I can sweat a pipe when necessary. So when it came time to add onto the house I accepted the whole challenge which included the heating system. That was 10 years ago and the heat has never given me a problem until now. When the system temperature nears 180 degrees both my PT valves (I have 2 boilers) begin leaking and at 180 they are both producing a steady dribble. At 180, the pressure is about 33 psi. When the system was new it ran just under 30 psi at 180. My cold system pressure is 12 psi. I’ve replaced both valves but the new ones leak too. I haven’t found any valves rated at anything higher than 30 psi except those for domestic hot water heaters and I’m not about to use those. Any suggestions?
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Your expansion tank is waterlogged.
OK, how do I un-log it?
Depending on your expansion tank. The new types have a bladder in them to prevent the air space and water mixing.
In yours the bladder might have failed. Let the system cool to room temp, get the replacement tank ready with the pipe dope applied to the threads. bleed off some of the water from the system till pressure reads Zero. Unscrew the old unit could be heavy with the water in it, be ready.
Screw on the new unit. Refill the system.
If youhave the old type with out a bladder in the expansion tank, drain the system and the expansion tank most have a valve on them for this. Refill the system
I have a bladder tank. I'll try a replacement. I'm surprised it only lasted 10 years.
You may also have a bladder tank that is too small for the amount of water you have in the system. This is common in older homes that were converted from big radiators or steam.