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Leak in underfloor heating

Discussion in 'Plumbing and Central Heating' started by diggerdga, 19 Nov 2016.

  1. diggerdga

    diggerdga

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    Hi, I'm desperately hoping that some clever person out there can help... we have recently installed a water underfloor heating system connected to our combi boiler in our kitchen extension. It is just two loops (both about 50m in length) back to the manifold. Unfortunately the pressure in the underfloor pipes keeps dropping, from 2 bar to 1 bar overnight. We have the underfloor isolated so it isn't a leak elsewhere within our central heating system. We therefore have to conclude that somehow we have leaks in the underfloor pipes, presumably caused when the screed was poured. A plumber suggested I get a thermal imaging camera for my phone and that was supposed to show where the leaks are. Having now tried on many occasions with the thermal imaging we just can't get any decent picture definition of the pipes (we just get a mass hot area showing across the whole floor) and we believe that is because the pipes are now under the layer of screed then under a layer of adhesive which is sticking down a plastic tiling de-coupling mat then with more adhesive and tiles on top. So, does anyone know if there are any other ways of finding the location of the leak before we have to remove all of the tiles, rip up the de-coupling mat and then dig up the screed? Please!
     
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  3. snb

    snb

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    You need to determine which loop is leaking first. Are you certain you have a leak in the underfloor? did you install an extra expansion vessel for the system as the boilers own expansion vessel will be unlikely to cope with the extra volume of water.

    Guess you didn't have the pipes under pressure when the screed was laid?
    Pressure test each loop separately with air. you are more likely to be able to hear the leak if it is big enough.
     
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  4. picasso

    picasso

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    Bit of a long shot but I have heard of this working, get a bottle of strong (cheap) aftershave and put in in the ufh pipe, do one loop at a time, with a bit of luck you should be able to smell roughly the area of the leak, or if you fancy spending a bit of money there are companys that can fill the pipes with an inert gas and can sniff where the leak is .
     
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  5. Having isolated the leaking loop, if you take images as the floor heats up, you may be able to spot the area that bleeds from one lop to another as the water spreads. Look for an odd pattern of heat spread.
     
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  6. oilboffin

    oilboffin

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    Just isolate each loop cap off one end then use air and pressure test each separately,you will then know which one is the bad one.To test take the pressure up to 4-5bar.Bob
     
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  7. diggerdga

    diggerdga

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    thanks all, really appreciated. I must admit I can't imagine a gas managing to get through the screed, de-coupling mat, adhesive and tiles in the right sort of place but that might just be my lack of knowledge of how inert gases work. It's one we will try though if we have to. In the meantime I would like to try pressure testing with air as suggested - how do you do this though? Is there a special tool I need (pump?) or the like? To answer snb's comments, no we don't have a seperate expansion vessel, that's something I haven't been recommended - our system is only in one roon (20sqm) might that be why? Also you are right, the pipes didn't get pressurised before the screed was laid (I thought I had but did it wrong so only filled the valve (oops!)).
    I will also give the after shave a try, I'm game for anything at this stage that might prove or disprove the leak.
    Does anyone know if Fernox leak sealer or the like would be worth a shot if it is only a small hole?
     
  8. mcmoby69

    mcmoby69

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    Check expansion vessel first, needs to be correct pressure and size for the volume of water in your system.
     
  9. steve32

    steve32

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    If I'm reading this correctly the underfloor heating was not tested before the floor was laid oh dear.
    No leak sealer will not work.
    Does the pressure drop to zero.
    If a system is filled to 1bar cold the pressure will raise when it is hot then drop when it cools.
     
  10. oilboffin

    oilboffin

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    You can get an attachment to fit on one end with a scraider valve on so you can pump it up you can just cap the other end.Bob
     
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  12. Going back to your opening post, at the end of the day, if there is a leak in one of the loops, then you will have to rip that side up and start again, and unless you are confident to only have to do one half, and match it to the same level as the other side, then the whole lot will have to be done again

    How are the loops and the manifold isolated from the rest of the house. It looks as though the loops weren't filled with water when the screed was poured, and if not, I suspect one of the pipes was walked on, and squashed. If there's no expansion vessel on the UHF system, then how is the expansion of the heated water handled if it's isolated from the rest of the house. Is it possible that the leak is in fact in another part of the house.
     
  13. dilalio

    dilalio

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  14. oilboffin

    oilboffin

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    Nice oneDilalio I couldn't find it I'm going to thank you mate.Bob
     
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  15. diggerdga

    diggerdga

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    thank you, I will purchase one and give the air pressure test a try. In the meantime I'm not sure what to make of our lack of expansion vessel for the underfloor, it has never been mentioned by either the plumber involved or the merchants that sold us the system. I assume therefore they believe that the one in the boiler will be sufficient? As I mentioned it is only one room's worth of underfloor heating that we have added to the system. I'm pretty confident that there isn't a leak elsewhere in the system as when the underfloor system is isolted the boiler pressure remains constant - it is only the gauge on the underfloor that is dropping. Unfortunately the pressure does drop even when there is no heat in the underfloor system (I left it for 4 days to make sure it was fully cooled down, filled up again and then the pressure dropped overnight). I'm starting to wonder if it could be a faulty gauge but that seems unlikely as it is only a mechanical thing. I guess the air pressure test should tell me once and for all if I do have a leak
     
  16. oilboffin

    oilboffin

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    Once you've got it pressurised brush soapy water on the joints to make sure you have no air leaks.Bob
     
  17. dilalio

    dilalio

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    Are you sure the loops under the floor are continuous? Did you see it before screeding and that there's not a joint/fitting sneaked in there somewhere?
     
  18. oilboffin

    oilboffin

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    That would be a problem .Bob
     
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