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Central heating pressure drop, slab leak?

  • 09-02-2020 11:29am
    #1
    Registered Users, Registered Users 2 Posts: 98 ✭✭


    Hello, moved into a house 2 years ago, had an oil boiler which didn’t do a great job and upgraded to gas just before Christmas. Plumber has been back a few times and put in leak sealer but the pressure is continually dropping. He reckons it’s always leaked a bit as the old system had a pressure relief valve letting cold water into the system all the time. Problem is the pipes are all under the floor, underneath various tiles, laminate and carpet flooring, on top of concrete.

    I’ve got my hands on a thermal imaging camera to at least find the pipes and in the areas where I could take up the carpets I found a lot of hot spots in the floor, some as hot as 45 degrees.

    Before I go digging around in the concrete (as the plumber has said he could re-pipe from the ceiling for between €5k and €10k), just wanted to ask for any advice before I do this, what to look out for etc

    Edit: added pictures of the worst offending area (45 degrees in the concrete)
    Edit 2: it’s been about 0.5-1.0 bar drop a day. He’s now installed a pressure relief valve set to 0.25 bar so that we don’t have to keep topping it up for now (caused a lot of air in dass)


Comments

  • Registered Users, Registered Users 2 Posts: 98 ✭✭Stern


    So, went digging around. 3 holes, close to where the pipes come out of the utility room (that’s where the gas boiler is and they go in).

    1st hole at first junction, found that while the 2 main pipes are insulated (though insulation was very damp/not quite dripping, and hence came apart very easily), we couldn’t see an actual leak.

    2nd hole as close to the wall (to the utility room) under which the pipes come out as we could, we found they’re not insulated there and are directly embedded in the concrete. We stopped drilling at that stage so as not to damage them.

    3rd hole at the very warmest spot, we found insulated pipes again but a lot wetter. I turned on the heating again for a while but the wetness didn’t seem to increase. Will check it again tomorrow after it’s been running a day to see.

    Overall conclusions so far: pretty sure there’s a leak somewhere in that area, though haven’t yet found where exactly. The hot spots we’re guessing are due to the uninsulated pipes directly where they come out and also where the junctions are, though at the third hole we didn’t dig far enough out to find the junction, and it was getting late so we put insulation in the hole and put the carpets back down as I’ll be gone next week and I didn’t want the better half running around a house with no carpets.

    I’ve contacted the plumber and let him know the findings, to be honest I’m not expecting much back beyond: “Keep digging if you feel like it and let me know if you find anything conclusive, but even if you do sounds like you need new pipes anyway and might have more leaks even if you find the first one”. I wouldn’t blame him, but any other suggestions anyone might have on what to do next? I’m really trying to avoid replumbing the house (whether it’s in the floor or the walls).


  • Registered Users, Registered Users 2 Posts: 58 ✭✭howa .223


    I have had the same issues, house built in 1990. as i have a vented heating system its not so easy to see the leak however i was in my attic and heard the water drip into the small tank, which i then found out could potentially be a leak in my heating system.
    Got the system pressure tested where it showed a very quick pressure drop. easily found out the underfloor copper was leaking. Rather than trying to find the actual leak i decided to redo the pipework.
    I didn't go down the walls for each rad as you said but found 3 points where pipework came from attic so i could reduce the amount of digging moved Radiators to internal wall for shortest pipework. Maybe an option. My hot press in upstairs it made my work a lot simpler and less intrusive to daily life i done each section in a weekend.

    As my home is a bungalow with dormer extension i went that way around the issue. Still not pleased but had quotations of 12-15k to dig up redo all the pipework and then the cost of re flooring and tiling halls etc.
    Done it myself as i said costed my time and 4,800 in materials. No grants available as i'm not SEAI registered:)
    i would recommend getting 4-5 quotations but also an itemized list of materials from whoever is doing the job, dont be afraid to go over and question the quantities. Maybe even get your own quotations for the materials from suppliers in your area.


  • Registered Users, Registered Users 2 Posts: 200 ✭✭Paullimerick


    Firstly your plumber should be able to identify if u have a leak. And in which pipe. Using a compressor. Very simply. And if you have holes already in the floor. You may even hear in. Pm me if u want more info


  • Registered Users, Registered Users 2 Posts: 58 ✭✭howa .223


    Firstly your plumber should be able to identify if u have a leak. And in which pipe. Using a compressor. Very simply. And if you have holes already in the floor. You may even hear in. Pm me if u want more info

    If it's on the hot or cold feed to a tap it's easy but if it's the heating circuit it won't be so easy to identify if you have 1 or 20 leaks as you would have 3/4" feed and return then each rad is reduced down to 1/2". If you pressure test the system it will identify a leak but unless every fitting and pipe is exposed no guarantee you'll find the exact pipe or fitting.
    Then you will never be sure about the rest of the house as they said some pipe has been laid directly exposed in the screed.


  • Registered Users, Registered Users 2 Posts: 200 ✭✭Paullimerick


    Well I'm a plumber with over 20yrs. To me I think it would be easy enough find. But each to their own. Won't argue with your theory


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