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Homeowner with a weepy pressure relief valve

Tom_81 Member Posts: 6
I have a Burnham boiler with 5 zones with DHW. I'm getting more water from my pressure relief valve than I should. It doesn't appear to be the PRV, as the pressure gauge looks to be right about or slightly above the 30psi mark when the boiler reaches 170-180.

So, I've found that likely causes are: a) defective pressure regulator, b) expansion tank issues and c) a leak in the coil of my Superstor DHW tank.

My system is 7 years old and I've never touched the expansion tank or Watts feed valve/pressure regulator. The Watts literature says the screen should be cleaned 2x /year. Yikes! Really? It appears that I can regulate the water pressure properly with the adjustment screw, but I haven't disassembled or changed the unit (WATTS 1156), so maybe my pressure regulator is bad? Our water is pretty hard if that matters.

Also, I just checked the expansion tank and the air pressure measured about 26psi with the water temperature about 90 and water psi about 14. The expansion tank is not leaking externally and doesn't appear to be leaking internally or saturated as there is a big difference in temperature from the top (water side) to bottom (air side) when the boiler fires and when I checked the air pressure, I bled a little and only air came out.

Is it possible that there is simply too much air in the tank? Assuming the expansion tank was charged to 12psi when installed 7 years ago, how could it gain pressure over time? Should the air psi and the water psi be about equal (12-15 psi) when the system is cool?

Anything else I should check? I am planning to check and probably change out the Watts 1156 anyway.

Thanks in advance.


  • Jim Erhardt_3
    Jim Erhardt_3 Member Posts: 80


    There shouldn't be any water coming from the relief valve under normal operating conditions. The relief valve is a safety device and the fact that it's opening indicates a problem.

    The fill valve (pressure reducing valve) is factory set at 12 PSI. The air charge in the expansion tank is also 12 PSI, but must be checked with no pressure in the system - or the tank disconnected from the system. An expansion tank can lose its air charge over the years, but cannot gain "more air" on its own.

    A bad heat exchanger in your indirect water heater, a bad (or improperly sized) expansion tank or bad PRV could all be the cause. I would have the system checked by a qualified professional, and make sure to have the relief valve replaced too.

    Jim Erhardt

    Product Manager, Hydronic Products

  • martin
    martin Member Posts: 144
    I Agree

    Pres. on boiler should only be 12-17 psi and should not raise a bunch when heating, if it does then problem with exp. tank But the smart thing to do is get a pro to fix it right and have some piecr of mind.
  • Tom_81
    Tom_81 Member Posts: 6

    Thanks for the replies, guys. I'm with you on it being a problem and fixing it. When I check the air pressure in the expansion tank, I get 22-23 psi with no pressure on the water side of the system, but I have not taken the tank off the system. My total rise is about 21-22 ft from the basement floor to the second floor baseboards, so the question I have is, why would the installer put 22psi in the tank? I've changed out the feed valve/pressure regulator. Any reason why I shouldn't lower the pressure in the expansion tank to 12-15 psi before I put the system back on line to test?

  • John Faust
    John Faust Member Posts: 13

    You should be fine with 12psi. To get water up 21' takes 9 psi. Adjust the pressure in the exp tank to match 12psi.
    Most relief valves are set at 30psi which can vary by 5psi up or down - whoch explains the weeping.
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