Leaking pressure relief valve


Old 05-19-14, 07:46 PM
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Leaking pressure relief valve

I have a boiler with a leaky pressure relief valve. I noticed the pressure a little high on the boiler, I also noticed water inside the expansion tank for the hot water tank. Will the bad expansion tank cause leaks from the boiler relief valve or do I have other issues? I dont know what info I need to supply, any help would be appreciated.
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Old 05-20-14, 08:35 AM
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Start by reading these two 'sticky' threads:



Please identify for us which type expansion tank you have:

Do you have the type that looks like a propane grill fuel tank? or a larger steel tank in the joists above the boiler?

The expansion tank you mentioned... connected to the 'hot water tank' ? It's possible that you have an expansion tank on the actual domestic piping to the water heater and this is not connected to the boiler piping. Need to clarify what you are looking at there.

Take some pictures...
Old 05-20-14, 04:38 PM
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Thank you for the reply, I have the propane bottle style tank. The tank is attached to the line that runs down to the water heater which is marked "cold".

There are two tanks, the one we speak of and one on the boiler, both of the relief valves are leaking. I hope you can see everything from the pictures.
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Old 06-10-14, 07:19 AM
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An expansion tank hanging below the pipe it is connected to and being full of water that comes out the Schrader air valve is no longer performing the function of expansion tank and needs to be replaced. Depending on whether the domestic water system has a check valve on the main inlet, the water heater temperature & pressure relief valve will frequently trip when a new tankful of water is heated up if the expansion tank is full of water or absent.

A similarly waterlogged expansion tank on the heating piping system can result in the boiler relief valve tripping. This is less likely if there are air pockets here and there in the heating piping or in radiators.

If the expansion tank does not let out water from its Schrader valve then you can recharge it and the pressure relief valve should no longer trip.

Particularly if the relief valve has tripped a lot, it could accumulate sediment or rust inside that causes it to not close all the way and leak a little constantly.

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