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Way to fix possible pinhole leak in copper pipe encased in concrete?

Flotsam Member Posts: 4
edited November 2016 in Domestic Hot Water
I have a 52 year old Mid-Century Modern home with radiant in-floor heating provided by a boiler and copper piping encased in concrete. I've recently developed a leak (which we've been able to trace to somewhere in the 1 1/2" return line from the living room loop back to the boiler) which is allowing enough air to enter the system such that bleeding is now required every 5 to 7 days. Since jack-hammering the floor up to replace the pipe really isn't an option, before we consider eventually having to abandon the system entirely and attempting to retrofit some kind of forced air system, is there any way to possibly plug what appears to be - at least for the moment - a pinhole leak in encased copper pipe? We've considered the automotive radiator leak fluids for example, but are looking for either experienced advice or other outside-the-box ideas.


  • Leon82
    Leon82 Member Posts: 684
    That probably is not good for the boiler but it may buy you some time. It sounds like you have slab on grade with a finished floor over the concrete. So you probably will need to explore the forced air or baseboard or panel rads
  • kcopp
    kcopp Member Posts: 4,187
    Fernox makes this product..
    You can give this a try and it will by you some time. You are prob looking at jacking up the floor OR finding a way to get the return out of the floor and above ground.

  • Zman
    Zman Member Posts: 7,446
    Usually you are getting air because water is leaking out and being refreshed with airated water. Air will not enter a pressurized system through a hole.
    I would try using an infrared camera to locate the leak and repair.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • ratio
    ratio Member Posts: 3,402
    You should be able to pinpoint the leak with a thermal camera of some sort, possibly even an IR thermometer. I bought a Fluke VT04 for the purpose & it worked swimmingly. If you can find the leak, a small hole can be opened & the repair made, & you might not have to abandon the radiant floor.
  • Gordy
    Gordy Member Posts: 9,537
    May I ask have you isolated the system from make up water to see how long it holds pressure?

    How have you traced the leak to the 1 1/2" pipe?
  • Flotsam
    Flotsam Member Posts: 4
    Gordy, the system seems to lose 1 psi every 30 minutes or so, it's hard to say because the gauge we're looking at is old and we don't trust it completely. What brought the issue to our attention in the first place is the need to bleed the system every week or so or else the living room loop pump begins to just freewheel.
  • Flotsam
    Flotsam Member Posts: 4
    As some of you have guessed, the system in encased in a slab, unfortunately under $50,000 worth of Italian tile. Jack-hammering even a small portion is simply out of the question given the inability to match replacement tiles to the original. The surrounding walls are either brick or floor to ceiling glass, so adding baseboards or moving the return above ground is essentially impossible as well. Kind of a perfect storm.
  • hot_rod
    hot_rod Member Posts: 19,260
    If you are sure it is a leak in a loop, the companies that do pipe relining may have a fix. I read an article where they relined some underground, pressurized glycol PVC chiller lines in Colorado. I'm not sure how small they can reline.

    I get "Cleaner" magazine, my wife is in the drain and sewer business, and every month they have unique relining articles.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    rick in Alaska
  • SWEI
    SWEI Member Posts: 7,356
    Is this an Eichler by chance?
  • Flotsam
    Flotsam Member Posts: 4
    SWEI, no, Jackson Hallett. Hallett worked with Alden B Dow (a protege of Frank Lloyd Wright) in Midland, Michigan.
  • SWEI
    SWEI Member Posts: 7,356
    edited November 2016
    Sounds like a fun project.

    My Dad bought a brand new Eichler in San Mateo just before he got married. I learned to crawl on those heated floors.

    We're going to http://www.modernismweek.com/ next year for the first time.
  • Danny Scully
    Danny Scully Member Posts: 1,397
    edited November 2016
    How is retrofitting forced air more feasible than repairing the leak? Thinking ahead a bit, but just an idea, you can install radiant in a ceiling as well.
  • Paul Pollets
    Paul Pollets Member Posts: 3,616
    The problem with older copper RFH systems is that another leak could develop after fixing the first. Concrete embedded piping is deleterious to copper unless it is sleeved or wrapped in mil tape
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    If the slab cannot be fixed and baseboard cannot be used, can you use radiant panels on the walls or ceiling?
    EBEBRATT-Ed Member Posts: 13,423

    I have never used it myself but I know of a hockey rink where the piping in the slab leaked and this did the trick. Works on copper plastic and steal pipe
  • nibs
    nibs Member Posts: 499
    Coming right out of left field, Detroit Diesel has a product which seals pinholes in steel cylinder liners, it may be that it needs the fire of the fuel to cook it, but a call to their engineering dept may yield positive results.
    Met a guy who had used it with very good results.
  • billpipe
    billpipe Member Posts: 1
    You can try Boiler Solder by Silverking. It works similar to car radiator stop leak. The product can be put into the system with an old fashioned force pump. It searches out the leak by being drawn to oxygen. This is a one time only application, as too much will build up on the pipe walls just like cholesterol in an artery.