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water pressure too highr

Nick Babb
Nick Babb Member Posts: 1
the water pressure on my Weil-McClain hot water boiler is, for some reason, going up to 35 lbs, instaed of operating at its normal setting of 12 lbs. This causes the pressure relief valve to seap water, as it should. What could be causing the pressure to suddenly be so high? It has never done this before; the boiler is 18 years old. Thanks.


  • It can be one of three things:

    1. Pressure reducing valve seeping by - do this drop the pressure down to around 5 lbs pressure by draining off some water with the water shut off, then turn the water on and watch the gauge if it climbs past 12 lbs the PRV needs cleaned or replaced.

    2. If it stops at 12 lbs and remains stable now bring the burner on, if the pressure goes up and does not stop you are losing expansion on your system, replace the expansion tank.

    3. Do you get domestic hot water from the boiler? If so the city water feed to the tankless coil is in excess of boiler pressure and a leak in the coil will cause pressure to build up. To test shut the water off to the tankless and if the pressure does not rise in the next 8 hours then the coil is leaking and will have to be replaced or removed.
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