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Weil McLain oil furnace psi

TomGan Member Posts: 15
I have a Weil McLain oil furnace (16 years old). Woke up the other morning to several gallons of water on the basement floor from the pressure release valve doing it's job. PSI was 32 and release valve set at 30. The plumbers came and did the following: 1) replaced the pressure release valve and the water feeder valve with brand new ones. The new water feeder valve was pre-set to 15 psi. They replaced the expansion tank with a brand new one also. They also checked the water pressure coming into the house from the city water line. It was 80 psi so they installed a pressure regulator there and set it to 60 psi. They also checked the 80 gallon Weil McLain water heater as they said sometimes that is the problem. That checked out okay. Lastly they drained some water and brought psi down to 15. Over night it slowly crept back up to 30 psi. I feel like we have tried everything. Plumber coming back later today, but would love to get some advice from this forum. Do I need to replace the entire furnace?


  • SuperTech
    SuperTech Member Posts: 1,792
    You probably just need to replace the indirect water heater. It sounds like a pin hole in the coil is causing the tank to pressurize the boiler.
  • kcopp
    kcopp Member Posts: 3,990
    Or a tankless coil pinhole leak....
  • Jamie Hall
    Jamie Hall Member Posts: 18,977
    But the bottom line is that it's not the boiler (furnace). Don't let them bamboozle you into replacing that.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    HVACNUT Member Posts: 4,597
    How did they test the water heater? Are there isolation valves for all the loops?
  • TomGan
    TomGan Member Posts: 15
    Thank you for all these comments. I know very little about these issues (I'm and Accountant). I'm not sure how they tested the water heater but will ask them. A new Viessmann 50 gallon tank arrived this morning and they will install later today. My old one is 16 years old so I figured best to replace anyway. Hopefully this fixes my psi problem. I will report back. Thanks again for all the helpful comments.
    EBEBRATT-Ed Member Posts: 12,024

    Do this:
    1. shut the manual valve feeding water to the boiler off. Then leave it off for a day or so and watch the pressure.

    2. If the pressure still goes up then the problem is probably your water tank. Shut the cold city water off to the tank and leave it for a day. Turn the boiler water back on. You will have no hot water.

    Do these steps one at a time so you can find the problem
  • pecmsg
    pecmsg Member Posts: 2,901
    edited March 2020
    That's a lot of parts to be changing, and all easily checked to see if there working or not!

    Hope your not paying for the next call.
    STEVEusaPArick in Alaska
  • TomGan
    TomGan Member Posts: 15
    Thank you. Looks like replacing the water heater did the trick. The new one has been in place for about 20 hours now and all good. PSI is now ranging between 16 - 19. Thanks again, for all the helpful comments.