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air leak - rookie needs advice

I'm in the process of building a house in the middle of nowhere southern Idaho. We covered about 3000 sq feet with radiant heat pipe in basement concrete -- 3 zones. Pressurized the system at 100psi and it maintained it well. That was in September. Now we are finishing dry walling. I pressurized the system the other day to 90 psi and it dropped to 85 psi in a few days...dropped another 2 psi the following day. It stayed pressurized throughout framing and I can't think of anything thats been shot into the concrete since. I guess my question is should I be worried about the drop and if so what should I do about it? The guy who was doing the radiant heat for me unfortunately passed away mid project and there is nobody around here who knows much about it. Any help appreciated.


  • mars_6
    mars_6 Member Posts: 107
    the ambient air temperature drop of the air in the loops will fluctuate depending on what temp the air is introduced into the system. I would re pressurize the system at the current ambient air temp and if there is no fluctuation you are good. Air acts like a liquid and will expand and contract with temperature change. Matt
    Matt Rossi
  • Ironman
    Ironman Member Posts: 7,342
    I agree with Mars answer and would add: chech your manifold connections and the actualt test gauge itself for minor leaks.

    Was O2 barrier tubing used?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
    edited February 2015
    +1 with Ironman, especially if you have the fiber washers for the manifold connections.
  • icesailor
    icesailor Member Posts: 7,265
    May I add, have you ever seen a car tire with "a slow leak", no matter how slow, not go completely flat if given enough time?

    If you use an air compressor to provide the air, air compressors have devices designed in them to dissipate heat. The heat of compression. When the air de-compresses, it cools. When you release the pressure, the air cools from de-compression. The air gets hot from compression. Why they tell you to check your tire pressure with the tires cold and not after you have been driving.

    The volume of air in your floor isn't all that great. Neither is the amount of air needed for it to drop in pressure.

    Try some quality gas leak detector liquid on any exposed connections. Like STEVEusaPA said. Check the connections with gaskets.
  • hot_rod
    hot_rod Member Posts: 21,835
    does it ever drop to 0?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Gordy
    Gordy Member Posts: 9,546
    Also remember your only holding 12 psi under operating conditions. I think as been said its temp variation of the air.
  • kendallmil
    kendallmil Member Posts: 2
    I pressurized it to 90psi last Tuesday. It was 85 on Friday.
    never has dropped to zero. i'll check the connections. manifolds aren't on yet...its all just been linked so we could compress it for the initial inspection. i'm guessing its the concoctions where it has all been connected. i sure appreciate your input everyone. i guess if i can't find a leak i can pressurize the individual zones and try to isolate it. KEEP YOUR THOUGHTS COMING!!! I APPRECIATE IT!!!!
  • SWEI
    SWEI Member Posts: 7,356
    What pressure was in the tubing when the slab was poured?