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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

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    • CommentAuthorRex
    • CommentTimeSep 1st 2017
    What ho one and all,

    Because I built my house, I am obviously an expert on all domestic issues!

    Another neighbour has asked me about her rising damp issue. As it happens, she had cavity
    wall insulation some time ago. However, after some investigation by Rentokil and a local
    plumber to check if the heating system was faulty, she has told me that back in June, she
    had the heating system power flushed.

    Apparently, she was warned that because of the pressure, there is a remote risk of a
    subsequent leak. It seems the leak is under the concrete floor beside a bay window, where
    there is a small radiator.

    I know next to nothing about power flushing, and although I realise that is can stress the
    system, is it likely to cause a leak somewhere under the floor, where all the pipework is
    encased in concrete screed?

    Thanks and toodle pip

    • CommentAuthortony
    • CommentTimeSep 1st 2017
    Copper pipes encased in concrete screed are very likely to pinhole through corrosion with or without power flushing, the older they are the more likely rising to above 50% after 25 years and virtually guaranteed after 35.
    • CommentAuthorJeff B
    • CommentTimeSep 1st 2017
    A previous house I owned had leaking CH pipes in the screed after 7 years. The pipes were plastic coated except for the soldered joints - guess where the leaks occurred? This was without powerflushing (was that around in 1977?).
    • CommentAuthortony
    • CommentTimeSep 2nd 2017
    Where no plastic, on the corner of elbows too
    • CommentAuthorCWatters
    • CommentTimeSep 4th 2017
    Before digging anything up it would probably be worth trying to isolate that section of pipe and doing a pressure test. eg pressurise it and leave it overnight to see if there is a pressure loss.

    You can also get Central Heating Leak sealers from places like Toolstation or Screwfix but it would be worth confirming if there really is a leak first and where it is.

    Did your neighbour say how much she paid for the power flush? Some companies charge rip-off prices for power flushes that aren't always necessary.
    • CommentAuthorRex
    • CommentTimeSep 5th 2017
    Thanks for the comments. I have passed them to the neighbour and the ball is in her camp.

    • CommentAuthorringi
    • CommentTimeSep 21st 2017
    Try using a leak sealer camical, it may work and save a lot of cost.
    • CommentAuthorCX23882
    • CommentTimeSep 24th 2017
    Last year I had an under-floor leak (45 year old copper in screed). I was losing pressure when the heating was off within 3-4 days. Thermal imaging using a cheap Flir One showed a few suspect areas, but nothing definitive (could just be joints where the pipe was closer to the surface).

    A single 250ml tube Fernox F4 Express (less than £20 on eBay), squirted in via the magnetic filter made a huge improvement. I fed in half of the tube, and let the system run for a week, and then gave it the rest of it. I still lose pressure, but very gradually. Since the heating went off in April, it has kept above the boiler's warning threshold for pressure.

    I'm under no illusion that it's going to leak again at some point, but it delayed the massive repipe cost by a year so far. There is a risk of knackering the boiler, but to be honest if I do the repipe it would be new radiators too, and then might as well replace the boiler at the same time. No way the new pipes will be run in the floor again though - surface mounting on boxing for me from now on. Same with other plumbing, audio-visual and network cables - it's so much easier to have a panel that can be removed to gain access when things go wrong.

    I was sceptical of the product, but it really does work. Thermal imaging of the radiators shows nice even heat distribution and no blockages due to the sealer. No obvious problems with the boiler either.
    • CommentTimeSep 24th 2017
    Posted By: CX23882No way the new pipes will be run in the floor again though - surface mounting on boxing for me from now on. Same with other plumbing, audio-visual and network cables - it's so much easier to have a panel that can be removed to gain access when things go wrong.

    I think the usual answer is to run services in conduits rather than surface mount everything.
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