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Rate of pressure loss

Discussion in 'Plumbing and Central Heating' started by whenisayjump, 15 Apr 2021.

  1. whenisayjump

    whenisayjump

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    Hello,

    We've recently moved from an un-pressurised system to a pressurised system and we're now having to deal with the weeps and leaks that go along with that.

    I've been digging around the internet, but I can't really see how best to gauge how much the system is actually leaking. We're probably losing about 0.1bar a day from the pressure gauge (we have a not large three-bedroom house with 7 radiators if that makes a difference?)

    However, on one leak detection website it says:

    "if you have concrete or screed floors, we recommend booking your Leak Detection only when your boiler is losing 1.5 bar of pressure consistently once every 24 hours or less"

    "However If you have suspended floors we recommend booking your Leak Detection only when your boiler is losing 1.5 bar of pressure consistently twice every 24 hours (or once every 12 hours) or less"

    This seems a huge amount compared to us.

    Thanks for any help!

    James
     
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  3. cross thread

    cross thread

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    You want no leaks really as adding fresh water on a regular basis causes corrosion
     
  4. whenisayjump

    whenisayjump

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    Oh no, I agree, and that's the place we're trying to get to. I'm just trying to get a handle on what sort of water loss I'd be expecting to see when I find the leak.

    Is 0.1 bar a drip, a weep, a torrent, a gush?

    James
     
  5. fixitflav

    fixitflav

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    As a rough guess, the air volume in your expansion vessel is about 12 litre (1/2 the total vessel volume) at pressure 2 barg = 3 bara. So 0.1 bar drop is a fraction 0.1/3, and volume of water out = 12*0.1/3 = 0.4 litre.
    I'm just a DIY-er, but the figures you quote, 1.5 bar twice in 24 h seem way too high. I wouldn't be happy with rate of loss.
     
  6. whenisayjump

    whenisayjump

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    Thank you. 400ml seems like quite a lot of water to escape over the course of a day, I would expect that to be very noticeable.

    James
     
  7. fixitflav

    fixitflav

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    It's a lot less than when losing 1.5 bar! It would be noticeable if the leak were somewhere visible, but it might not be.
    I believe there have been cases where the boiler heat exchanger leaks, the water going out with the flue gases. Perhaps one of the pros can comment.
     
  8. whenisayjump

    whenisayjump

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    The boiler is brand new so I'd hope it's not the innards of the thing... but it's always possible. We think there may be a slight 'weep' on an external drain cock so we're keeping an eye on that... it just doesn't seem like 400ml of water!

    Worcester Bosch say we can use Fernox F4 without voiding our warranty, so perhaps that's an avenue to explore.
     
  9. fixitflav

    fixitflav

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    OK good luck!
     
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  11. ianmcd

    ianmcd

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    How do you know you are losing 0.1 Bar per day ?
     
  12. ianmcd

    ianmcd

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    Absolute rubbish the lot of it
     
  13. fixitflav

    fixitflav

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    As per the original post, he's measured it. In any case, he asked Is 0.1 bar a drip, a weep, a torrent, a gush? and I estimated based on that, whatever the actual figure is.
     
  14. ianmcd

    ianmcd

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    And I asked how he is measuring it
     
  15. fixitflav

    fixitflav

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    From the pressure indicator, I would assume. Perhaps he'll confirm.
    In any case, he asked Is 0.1 bar a drip, a weep, a torrent, a gush? and I estimated based on that, whatever the actual figure is.
     
  16. ianmcd

    ianmcd

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    But you have no idea on the system volume so you cant just guess, do you know the difference between guage pressure and absolute pressure ?
     
  17. fixitflav

    fixitflav

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    I said it was a rough estimate, which is all he was looking for. I do know about gauge (not guage) pressure, why do you think I said in #4 "at pressure 2 barg = 3 bara"?
     
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