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Watts 174A Pressure Valve Seeping?

We built a home in the Colorado mountains 14-years ago. Radiant heat on main floor, baseboard on 2nd floor, Dow. 11’ height between bottom of boiler and baseboard. We have a continuing problem with random puddles of glycol seeping from the Watts 174A 30lbs. pressure relief valve. The valve has been replaced 3 times, along with the expansion tank. Original plumbing contractor totally incompetent. Had controls miswired so calling for heat 24-hours a day. Didn’t install shutoff between supply and return manifolds, one zone didn’t work. Plumber could not solve. General found that they installed one loop on supply, the second on the return. So I don’t trust any of their work. They set up system and expansion tank at 14lbs. Cold. It runs about 24lbs. Max. Temp is 180. With everything running. I installed a Watts pressure gauge with a pointer that display maximum pressure. Never over 25lbs. The plumber originally had a glycol mix at 70%. It is now down to 25%. I would appreciate any ideas on troubleshooting and what the cold system pressure should be set at. We are at 8,600’ but I don’t see how altitude would impact pressure. Thank you.


  • neilcneilc Posts: 659Member
    and how they relate to each other.
  • Jamie HallJamie Hall Posts: 10,293Member
    And maybe a sketch of how everything hooks together?

    Is the radiant heat on its own separate loop? Does it have a mixing valve to control the temperature? Pump? Radiant should never go over 120 -- if it's being fed 180, that's way too hot.

    With an 11 foot height differential, you really need only 15 psi at the boiler to keep the system happy. How is the pressure in the system controlled? Is there a pressure reducing feed valve? What is it set at? The expansion tank may not be large enough, but in any event it should be charged (isolated from the system and empty) at the cold operating pressure of the system.

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • BaeljbBaeljb Posts: 3Member
    I am attaching a diagram that I put together. I have photos, etc. but don't know how much I can send in one reply so I will create another response. Boiler Burderus G234X-38, Expansion Tank Amtrol RX-30, Pressure Relief Valve Watts 174A, Control Tekmar 361. There is a pressure reducing feed valve. I have it shutoff because if there is a leak, I want to catch it. I did install a low water shutoff for the boiler. The installer could not tell us the capacity of the system since he did not keep track of the amount of 3/4" pex he used.
  • BaeljbBaeljb Posts: 3Member
    Here are some more photos. The pressure relief valve is visible to the left of the expansion tank. The supply exists the back of the boiler horizontally, then there is a tee and a short piece of horizontal pipe to an elbow and then up to the relief valve.
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