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Pressure relief valve leaking into tundish after test

Discussion in 'Plumbing and Central Heating' started by Dazza Jones, 19 Apr 2020.

  1. Dazza Jones

    Dazza Jones

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    Hello.
    As the title, I tested the pressure relief valve that sits under my expansion vessel of my Central heating system. It worked, water was released into the tundish as expected. Thing is, it's now dripping at a constant rate, and the pressure in the system is reducing.
    She's giving it "why did you mess with it" and I'm thinking the same thing.
    Anything I can do or is it a replacement job?
     
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  3. Gasguru

    Gasguru

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    Indeed, why'd you mess with it...you could try upping the pressure to 2 bar with the loop and giving the valve a good blast to try and clean the seat but there's normally enough scale that they refuse to seal 100%
    Replacement required. Some can be cleaned but unless you're very careful it's easy to throw the calibration out when unscrewing/screwing the head back in.
     
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  4. Dazza Jones

    Dazza Jones

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    Read somewhere they should be tested as it's a safety feature.
    That will learn me....
     
  5. Gasguru

    Gasguru

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    Test in theory but in reality they nearly always leak.
     
  6. Dazza Jones

    Dazza Jones

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    Thanks Gasguru, I'll get it changed.
     
  7. Gasplumber

    Gasplumber

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    yes by someone who knows what to do to fix it and understand it.
    I’ve read I’m supposed to service my car every year!
     
  8. Gasplumber

    Gasplumber

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    Before you change it take it apart clean it and add silicone grease or replace it. It’s an easy job to be fair. just google how to fix a leaking prv
     
  9. oilhead

    oilhead

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    For the sake of what they cost, it's not worth bothering to try to clean it if a further flush does not clear it. When flushing, as said above, pressure up to 2 -3 bar, then hold the valve open to get a good flow through it.
    I was once admonished by an OFTEC inspector who was insisting I tested one on my annual inspection. I said I would do so if OFTEC would pay for it's replacement WHEN it leaked afterwards. He refused, as did I.
     
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  11. Mottie

    Mottie

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    I’ve tested mine and they’ve always been fine afterwards. They seem to have a stepped release and if you twist the red knob further they 'snap' back closed. I’m assuming this 'snap' hammers the valve against the seat to help sealing? Like the OP, I’d be getting grief from the wife if it all went wrong too. OP, just tell her it’s failed on inspection which is a good thing as it’s prevented a massive explosion. You’ll be a hero! :rolleyes:
     
  12. HERTS P&D

    HERTS P&D

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    Is that a MOT inspection tag line?

    Andy
     
  13. Madrab

    Madrab

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    What boiler is it?
     
  14. hard-work

    hard-work

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    On some boilers this valve is not cheap, or easy to replace.
     
  15. Dazza Jones

    Dazza Jones

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    I'm at work now so can't check, I want to say Ideal. The boiler is downstairs and the expansion tank and valve is upstairs.
    The rate of water coming out has reduced to a slow drip but someone is on their way out to look at it regardless.
    Many thanks.
     
  16. hard-work

    hard-work

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    picture?
     
  17. oilhead

    oilhead

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    I'm wondering now whether this is part of the central heating system or allied to a hot water cylinder. If so, you will need a G£ registered plumber.
    What colour is the vessel?
     
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