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How do I tell if I have an air or water leak

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bhowden
bhowden Member Posts: 28
I have a small radiant floor loop fed by a Taco X-Pump. The closed loop has an expansion tank with an air eliminator and a floor loop. I have had the system for about 3 years now. The water pressure drops by about 3 psi per year. The first year I pumped up the air in the expansion tank and watched. The second year I added a bit of water to get back up to 20 psi. The system is now back down to 17 psi. There are no visible leaks anywhere and the pipe (pex-al-pex) went down in a single pass with no kinks. Is there a trick to figure out if I am losing water out of the loop or air out of the expansion tank? I thought of a flir camera but I am guessing that the membrane in the tank will keep the water away from the side of the tank and that a picture wouldn't tell me anything. Any thoughts? Do tanks leak through the valve very often?

Brian

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  • HomerJSmith
    HomerJSmith Member Posts: 2,468
    edited April 2023
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    I'm having the same problem with a radiant sys and I'm trying to diagnosing it over time by trying to isolate loops and supply piping. There is so many places that a small leak can occur.

    When you let air out of a tire, a lot of air comes out between 35 psi and 25 psi. That's because air is compressible. Water is not. It only takes a cup or so of water loss to drop pressure to 0 psi.

    Without isolation valving it is a tough diagnosis.

    As my Dad use to say, "If the rate of evaporation exceeds the rate of drip, you don't have a leak."

  • Jon_blaney
    Jon_blaney Member Posts: 318
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    Replace the expansion with a plug. Let it sit over the summer. No loss of pressure, it is the tank, otherwise it is a water leak. I am betting it is the tank, leak in the diaphragm.
  • Jon_blaney
    Jon_blaney Member Posts: 318
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    Or/also: Remove the tank from the system, fill to 20 lb with no back pressure. Monitor the pressure.
  • HomerJSmith
    HomerJSmith Member Posts: 2,468
    edited April 2023
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    I think that I would just install a Webstone ball valve with drain on top of the tank. Makes it nice to put air in the tank without disconnecting it from the sys. Remember it's directional as to what drains.
  • Big Ed_4
    Big Ed_4 Member Posts: 2,807
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    Leak of 15% a year you will never find it , if it's not the expansion tank . Installing a pressure reducing valve , would move you on...

    There was an error rendering this rich post.

  • bhowden
    bhowden Member Posts: 28
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    I am inclined to agree with the opinion of "you will never find it"! I am not sure how a pressure reducing valve would solve the problem. It is a closed loop with no autofiller. My main dilemma is not knowing if I should top up the air or the water. I like the idea of adding an isolation valve to the expansion tank and will do that. Obviously if I close the valve and the pressure still drops over the summer I need water and vice versa. I am also guessing that I can close the valve, let the pressure out of the tank, remove it and weigh it to see if it is getting waterlogged. If I have no pressure in the tank and fill the top with water am I likely to half fill it or should I bring it up to 20 psi first and then add enough water to fill it to the top? I am guessing the latter as that is how it was installed in the first place. Either way, a valve will give me more options.

    Brian
  • hot_rod
    hot_rod Member Posts: 22,268
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    Push in the air stem on the tank. If the diaphragm is compromised and the tank is waterlogged, water, not air will come out

    with the tank isolated or removed pressurize to 25 psi don’t run the system, observe for a few days.

    I would not add an autofill as you will scale up the system by adding even small amounts of fresh water. Plus the O2 that comes along with the fill water.

    Determine if you even have a leak, if so, how much of a leak.

    Tiny pinhole leaks in hidden tube can sometimes be sealed with hydronic leak stop, Fernox has a product for that.

    one step at a time😗
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream