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Locating leak in Onix Tubing - Snow Melt System

tnaac5 Member Posts: 2
Hey gang. I ran through the discussion forum and saw several similar situations, but nothing exactly like my issue so I thought I would give this a shot. My company has been asked to evaluate and repair a snow melt system on a concrete slab in Montana. I haven't personally seen the system but we have a few photos and drawings (picture a kindergarten drawing of a bowl of spaghetti) from the original installation in 1999. It's 5/8" Onix tubing running what I'm told is a 50/50 glycol/water mix. The loops average 400' long and tubes are spaced 6" apart. Boiler fed, but I don't have any info on operating pressure or temp just yet. Platform is 235' long and roughly 12' wide. At least 19 different zones from the drawings we have.

We have two legs that are "leaking" and three that are "plugged". I'm looking for the best way to locate the leaks in the slab and any advice on clearing the plugs. We have a thermal camera and I'm hoping that may show some of the cold spots in the slab and indicate the approximate location of the plugs. We had also thought about pressuring up with helium and using a sniffer to try to isolate the leaks, although I have my doubts about that being incredibly effective outdoors. Since it's already snowing, it should be pretty evident what works and what doesn't but.....

Any advise on possible solutions, or methods of clearing the plugs or locating the leaks or simply a "whatever you do, don't ____________" would be GREATLY appreciated.


  • Jamie Hall
    Jamie Hall Member Posts: 18,924
    The thermal camera is the way to go on that. Start off with the slab cool and fire it up -- leaks should show up as hot spots and plugs as cold...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • hot_rod
    hot_rod Member Posts: 16,289
    any other history on the system? Did all the loops flow at one time
    Occasionally loops get linked during the pour and never flow from day one.
    If they are plugged often it is with a metal sludge, magnetite.

    Depending on how long they have been plugged and how much of the loop is plugged, it may be a tough go getting them all flowing again. Eighteen years of sludge goes a long way 😲

    There may be a point where not enough loops are salvageable, and a lot of hours tied up determining that.

    Orange or black colored tube?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Zman
    Zman Member Posts: 7,330

    The thermal camera is the way to go on that. Start off with the slab cool and fire it up -- leaks should show up as hot spots and plugs as cold...

    It helps to use a lumber crayon to mark the loops as the slab heats up. The hotter loops and shallower loops will appear first. The tubing will show itself very sharply at first and then begin to blur. Bring a cup of Joe and a fold up chair and just patiently mark the tubes as they appear and take pictures.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • tnaac5
    tnaac5 Member Posts: 2
    hot_rod - At one time, all the loops worked. Best guess is they started having issues prior to last winter. I have a feeling this system doesn't get much maintenance if any. Probably fired up when there's a chill in the air and shut down when the first 60 degree day happens and forgotten about until the next fall. Tubing is 5/8" black Onix. There are some photos from the original installation attached.

    Is it reasonable to think that if we could locate the plug or leak, the concrete could be broken up and the bad section repaired, tested and then poured back?

    Zman - This is going to take a LOT of Joe! Thanks for the tip!

  • hot_rod
    hot_rod Member Posts: 16,289
    yes there are repair couplings available. Determine how many leaks and the cause If it has a lot of leaks and a lot of plugged sections, is it salvageable and at what cost?

    Some of those rubber systems tend to sludge forever

    The sludge may be from O2 ingress breaking down the ferrous components

    Convert all the components to non ferrous materials
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • kcopp
    kcopp Member Posts: 3,990
    See if you can power flush the system out. get some cleaner in there and that will help get the stuff moving. I actually find Rhomar the best on Onix systems
  • John Ruhnke
    John Ruhnke Member Posts: 882
    In the old days Watts made onyx with out a decent 02 barrier. This was over twenty years ago. Anyway the 02 that leaked into the water ate any steel components (The Boiler) and turned it to a rusty type sludge. This plugged up the tubing and shortened the life of any steel components. What Hot Rod is talking about is that without solving the 02 problem even if you clean the tubes out the o2 will combine with the steel and continue to form this rust type of sludge and clog it back up again.

    I know that Watts solved this problem over 20 years ago and it has not been an issue since. So you don't need to worry about this on newer systems. I would take a picture of the tube and any markings, then call Watts and find out if this is the tubing with inferior 02 barrier or not. If it does have the older 02 barrier then you need to treat the tubing as if it never had a 02 barrier in the first place. Either add a 02 inhibitor or treat it like a dhw system and install only copper, brass or other non ferrous material.
    I am the walking Deadman
    Hydronics Designer
    Hydronics is the most comfortable and energy efficient HVAC system.