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Infloor slab Leak

I am currently having issues finding a leak in my in-floor slab. I isolate the both zone manifolds from system bring manifold pressure up to 50 psi each let stand for 24 hours psi will drop to 30-35 but will not drop to 0.

I keep losing glycol in the system every couple days I notice my glycol feeder tank has dropped, over the last 2 months I have lost close to 6 gal. I have isolated the boiler, checked heat exchanger and condensate traps for glycol and no issues there, I have searched the entire shop of boiler piping to locate a leak with no luck, only explanation is in the slab, but I cant get the pressure to drop to 0 to confirm leak in that zone so I can begin isolating each loop individually and terminate it from system.

what am i missing?

Thanks.


Comments

  • ratio
    ratio Member Posts: 2,873
    Get a thermal camera of some sort. I have a FLIR ONE Pro that I just love.
    Canucker
  • ratio said:

    Get a thermal camera of some sort. I have a FLIR ONE Pro that I just love.

    I don't know if an infrared camera will really show a leak that small.
    Often wrong, never in doubt.
    Zman
  • hot_rod
    hot_rod Member Posts: 14,871
    What happens if you let the system run at 12- 15 psi, does it still take on glycol?
    If it is a one level system you could run 5 psi, if that stops the addition of glycol.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • MeatBallZnGravY
    MeatBallZnGravY Member Posts: 6
    Its a single level shop 3500 Sq feet of in floor. it still takes on glycol when at running pressure of 12 psi, it has to run at that pressure due to factory installed pressure switch witch opens below 12 psi.
  • hot_rod
    hot_rod Member Posts: 14,871
    If you let the slab cool, then kick it on, I'll bet an IR camera would pick up even a trickle leak. We have seen examples of that posted here. Pinpointing even a pinhole leak. It shows up as a color puddle on the camera. Worth a try.

    Know anyone on the fire dept, they usually have good quality IR equipment :)

    If you have one in your area leakbusters.com will track down most any leak.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Zman
    Zman Member Posts: 6,792
    Is there anything preventing you from air testing the loops individually?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    DZoro
  • MeatBallZnGravY
    MeatBallZnGravY Member Posts: 6
    yes I can isolate manifold from system, I already installed pex ball valves on each supply and return pipe coming from floor so that is my next step, is to isolate manifold and put 75 psi of air pressure in each loop individually and monitor the pressure.

    over the last 2 days i have left heating system completely off with both zones isolated from system with 50 psi of water, over the 48 hours my pressures have dropped to 40 psi and 35 psi respectfully, if there was a leak would it not be at 0 if its completely isolated from system no expansion tank to keep pressure up?

    this is my delima, I credit the 10-15 psi drop as thermo-expansion as the slab begins to cool we drop pressure.
  • hot_rod
    hot_rod Member Posts: 14,871
    If it doesn't drop to 0 I doubt you have a leak. pressure will go up and down as it heats and cools. how much depends on fluid capacity, temperature difference, size of expansion tank, and pre-charge pressure adjustment.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • GroundUp
    GroundUp Member Posts: 1,272
    How large is your expansion tank? Is it possible the tank has a pinhole leak and you are slowly filling the bladder with glycol?
  • hot_rod
    hot_rod Member Posts: 14,871
    no visible leaks I assume? Test gauges are notorious for leaking around the Schrader valves very slow leak.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • HomerJSmith
    HomerJSmith Member Posts: 1,344
    edited January 2020
    Maybe you should remove each circuit, in and out, from the manifold, one at a time, and pressurize the loop and see which one doesn't hold pressure. Time consuming, but then you need to locate the leak or abandon that circuit. An IR camera should show banding if the tube is buried up to about 2" below the surface.

    Also, you may try to only run one circuit at a time with all the others closed off and see if you have a pressure drop. If you have a pressure drop with several circuits, I would look elsewhere for where the fluid is going.

    Is it possible that you are loosing water thru the Boiler Pressure Relief Valve and not notice? Is there a leak in the boiler HX?

  • nibs
    nibs Member Posts: 462
    Away for 3 weeks, came back & discovered that system had lost about 4 PSI. Topped it up & found we were losing about 1 pound every 3 days.
    Panic set in, started looking at the floor for damp spots etc.
    After about 2 weeks of watching & looking at floor, spotted a slight build up of lime on one of the copper pipes near boiler.
    The leak is not big enough to drip, don't be too quick to write of the possibility that the leak is not in the slab.