PRV Leaking

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Jdjd

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My pressure relief valve has started to leak. I'm 95% sure it is the expansion tank that is full of water, but would like to rule out the pressure reducing valve.

How can I test the pressure reducing valve?
 

Jadnashua

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First, if the PRV is leaking, rebuild, or replace it! Second, if the expansion tank is waterlogged, same thing...replace it. The only way to check a PRV for proper action is to have a pressure gauge installed and monitor it under various conditions. IF your ET is working, the pressure should remain where you've set the PRV. IF it gradually goes up or never is reduced and the WH is not running, the PRV is bad.
 

Jdjd

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The only way to check a PRV for proper action is to have a pressure gauge installed and monitor it under various conditions. If your ET is working, the pressure should remain where you've set the PRV. IF it gradually goes up or never is reduced and the WH is not running, the PRV is bad.

Yes, I plan to replace both the relief valve and expansion tank.

- Would I install a pressure gauge on one of the boiler drains?

- What is ET, WH?
 

Jadnashua

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ET = expansion tank
WH = Water heater
You'd need to find somewhere else to attach a pressure gauge...the boiler SHOULD be at much less pressure than the domestic supply (typically 12-16#). A washing machine supply, or the drain on the WH, or an outside hose bib, or nearly anywhere with an adapter. Or, if you want it more permanent, you could get one with a NPT on it, and install a threaded T somewhere after the PRV and screw one in permanently. Or, if you're really interested, install two, one before and one after the PRV.
 

Jdjd

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I've been googling this topic today. I found the following:

To test a PRV, shut off water supply, drain water to drop boiler pressure, turn on water, watch the pressure gauge for a few hours while not firing boiler. If pressure does not rise, or continues to rise past the set point, then replace the PRV.

Your thoughts on this?
 

Reach4

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Most PRVs are for the incoming city water. Initially the supposition was that is what you were asking about.

Had you posted in the Boiler Forum, then it would have been assumed that you were talking about some part in your hydronic heating system. It now appears that you are talking about a part of your hydronic heating system.
 
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