Boiler Pressure Relief Valve discharge pipe - copper vs plastic

Discussion in 'Plumbing and Central Heating' started by LittleJoe, 12 May 2021.

  1. LittleJoe

    LittleJoe

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    Hi,
    I'm currently helping my son renovate his first house and the house had a new boiler a few years ago and was fitted with a Condensing Boiler, Potterton Performa 24 ECO HE. The plastic Condensate discharge pipe and the 15mm copper pressure relief valve discharge pipe have been run out of the boiler cupboard and along the skirting boards through two bedrooms and out of the wall. The pipes are exposed to view and look a mess.
    As I am doing some work in the ceiling avoid above the kitchen which is also below the boiler cupboard, I thought I would take the opportunity to re-run the pipes through the ceiling void and out of the kitchen wall.
    The pipes will need to run through 6 joists. The boiler installation manual states that the pressure relief valve discharge pipe should be 15mm copper. It would make the job a lot easier for me if I was able to use 15mm plastic barrier pipe (Hep20, JG Speedfit) instead of the copper so that it will be easier to feed the pipe through the holes in the joists. Would there be any reason or problem in using 15mm plastic barrier piping?
    The first metre or so of pipe from the boiler I could use 15mm copper and then use plastic barrier pipe for the rest of the run.
    Any advice aprreciated.
    Thanks.
     
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  3. muggles

    muggles

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    You'd need to ensure that the pipe was suitably temperature rated for the application. Be aware that you're only supposed to drill holes in joists in a zone between 25% and 40% of the total span
     
  4. LittleJoe

    LittleJoe

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    Thanks Muggles. I'll try and establish the temperature rating of the 15mm Hep20 barrier pipe. I know it is suitable for central heating so I would have thought it should be OK for a pressure relief valve discharge pipe.
     
  5. footprints

    footprints

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    If the maker specifies copper then stick with it.;)
     
  6. MJN

    MJN

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    Bear in mind, however, that the pipe's usage would be in a fault condition which could be 110°C (I think that's the upper limit for overheat detection/restriction) at 3 bar i.e. superheated steam. You need to be confident the pipe can maintain its form and purpose for that worst-case scenario.
     
  7. oldbutnotdead

    oldbutnotdead

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    I believe (though please check this yourself) that Hep2O barrier pipe is rated for a limited number of overheat incidents (it is the only barrier pipe I know of which is allowed anywhere on solid fuel systems).
    That being said, every time the thing is serviced or (worse) CP12 inspected you'll have a fault recorded. Stick with copper, remember it has to run downhill
     
  8. ianmcd

    ianmcd

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    a PRV discharge does not have to be barrier pipe, if you are using PEX it will have to be rated temp wise for the PRV discharge standard pipe is not, but you can get stuff that is, some manus now use a combined Condensate and PRV discharge on standard pipe but they specify that so over rides other instructions, personally I dont see a problem with what you plan, but your house insurer may feel different if something happened , in the event of a genuine discharge at 3 Bar and extremely high temperatures you are looking at pressurised steam and not CH temp water as you assume , very rare, but that is why the safety device is there in the first place
     
  9. DIYnot Local

    DIYnot Local

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