Central Heating Pipes in concrete floor

Discussion in 'Plumbers' Talk' started by Troubled homeowner, Jan 13, 2020.

  1. Troubled homeowner

    Troubled homeowner New Member

    Hi, we found a long standing leak in the copper central heating pipe which was buried in the concrete floor.

    Plumber came out & removed the bit of pipe with the leak & adding a replacement bit in using copper pipe & joints.

    Initially, he left it so that one corner of the pipe was proud of the surrounding concrete floor & therefore we could not fill the hole & level floor.

    He came back today & used a metal strip with holes in to pull the pipe down.

    This evening with the heating on, the pipe has a tapping noise that comes & goes. It did not do this before he tried it down.

    So I have two questions:
    1. Is this tapping noise okay, will it go?
    2. How do we fill the hole, (we will wrap the pipes with tape first). What mix of concrete, can we use a product from B & Q, this one...

    Do we need to paint the concrete with anything tacky first?

    Really hope you guys can help. Photos attached.

    Attached Files:

  2. Jimbo

    Jimbo Screwfix Select

    This situation is not good news, especially at this time of year. No doubt this is a 1970s build.

    Basically, you need to extract as much of the piping as possible and replace it OR feed the radiators from upstairs, which might be easier.

    The pipes should be sleeved in insulation suitable for direct burial, like Armaflex class-O with the joints glued and taped over. This ensures the pipes can move about within and foam lining and never touch the concrete. Denso tape is not suitable as it melts at about 60*C.

    It doesn't look like you have trenches to lay the pipes in, so doing the job 'properly' will involve a lot of chipping out and mess. It can however be screeded straight over. The metal clip is completely unsuitable as the pipe needs to expand and contract, and steel I believe is harder than copper, so will eventually rub through it. The expansion is the cause of the failure in the first instance most likely, the pipes rubbing against the concrete at the bend. More problems will follow with the existing installation.

    Since the leak is long standing, check you system for pumping over if it's an open-vented (non pressurised) installation. Introducing a continual supply of fresh water is likely to have resulted in scale deposits where the cold feed meets the circulating hot (i.e. by the pump) which can block it. Also the system will need flushing and a magna clean fitted to get shot of the iron oxide resulting from the continual supply of oxygen into the system.

    I feel your pain, I am in the same situation at the moment. Really the best option will be to run the radiator pipes from upstairs and forget the pipes in concrete, though I have chosen to replace them, it is a very slow process as it also means new floors in my case.
  3. Troubled homeowner

    Troubled homeowner New Member

    Thanks for your reply, I completely agree that best case scenario is to take out & replace all, however, this is not an option, financially or time wise. The initial pipework didn't leak at a bend, it was a hole from corrosion where it previously ran under the door frame, however the rest of the pipes seem absolutely sound. We intend to add a sealing solution into the system to deal with any other potential tiny leaks.

    The pipes have already been directly buried in concrete for over 40 years, so ideally want to just put it back as it was.
  4. Jimbo

    Jimbo Screwfix Select

    40 years seems to be about the life expectancy unfortunately.
    Jitender likes this.
  5. Troubled homeowner

    Troubled homeowner New Member

    We have to make it work for the next few years, so any advice from anyone re how to fill the hole would be much appreciated. I'm not expecting it to last 20 years, 5 will do.
  6. That is ugly! Silk purse, sow's ear etc. If the corner is proud I would suggest that you remove the concrete below the pipe, wrap it in denso tape, or similar, and then "seasonally adjust" it as my colleague used to say. Aka stand on it so that the pipe is below floor level. Then any old concrete mix will do, it's not structural. If you're handy you can get the correct level otherwise just chuck the concrete in and use levelling compound and re-lay your laminate.
    BTW your original plumber was pretty hopeless, I would have done the above for you.
    Troubled homeowner likes this.
  7. Troubled homeowner

    Troubled homeowner New Member

    Thank you, that is my kind of reply. We'll get some Denso tape tomorrow & chuck some concrete over it.

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