Maximum Safe Mains Pressure

Discussion in 'Plumbers' Talk' started by Legolas-woodelf, Sep 21, 2012.

  1. Hi All.

    Last year the water board did some work on all the pipes in the road round our village, resulting, I think, in an increase in mains pressure.
    My question is, what sort of pressure is safe in terms of the risk of blowing pipework or joints?

    The setup is a mains stopcock in the garage, then the blue plastic pipe goes into the house and up to the loft before being converted to copper and heading out again through to kitchen, utility room and outside cold taps. Everything else is fed from a  balanced pressure reduced feed in order to balance hot and cold in the bathrooms from the unvented cylinder.

    Being a geek I've fitted three pressure guages; one on incoming mains, one on post PRV cylinder feed and one on the boiler heat circuit.

    Post PRV pressure is around 3.5 bar as per manufacturer's spec, maybe rising to 4 bar if the water heats without any taps being used for a while.

    The issue is the mains which is typically around 6 bar static, though I have seen brief peaks of 7 bar when taps/showers have been going on and off.

    Is 6 to 7 bar ok or is that putting a strain on internal pipework and joints? The last thing I want is a joint in the loft popping and flooding the entire house.

    I should say it's been fine for over a year and may have been ok before that as I don't know what the previous pressure was to compare (though my neighbours reckon the pressure has gone up since the work was done).
    Am I worrying unduly or should I fit a PRV in the garage near the stopcock so that all of the pipes inside the property are never subjected to more than 4 bar?

    My thanks in advance for any thoughts.
  2. Captain Leaky

    Captain Leaky New Member

    So long as the UVC is moderated down to 3 bar ( manufacturer spec) then you are simply being an old woman

    Houses round parts of Poole where I live have incoming mains of 10 to 12 bar. :)
  3. Helllooooo, Leggie - a very long time no see

    Thoughts on your pressure? Well, I think you are a lucky, lucky barsteward. Awesome pressure, man.

    Too high? Well, pipes and joints are tested to well above these pressures, so they certainly shouldn't 'blow'. And if there's a dodgy fitting there somewhere, reducing the whole caboodle down to, say, 4 bar is unlikely to make all the difference between it blowing and not blowing. Just what are the chancves of a fitting being so borderline?

    However, 7 to 8 bar is bludy high! I, personally, wouldn't be happy with the shock this gives the system when, say, a Fluidmaster/Torbeck-ish typer valve shuts off suddenly. Or even if you have ceramic disc taps - they shut off pdq, and a few years of that...

    Ok, you'd have to be unlucky, but with that sort of pressure I know that I would fit a PRV on the incoming - the cost is hardly crippling.
  4. Hi DA,
    Yes it has been a little while. Nice to hear from your good self likewise.
    It's good to hear that your kind of the same page as me too, i.e. yes it's a bit high, no it probably won't cause a problem, and yes, for thirty quid or so it wouldn't hurt to whack a PRV on the ToDo list. Which I reckon is what I'll do when I get round to it.

    Greetings to your good self too, Skipper.
    10 to 12 bar round the Poole area! I've just done a conversion and that's pushing 175 psi !!! :eek: That's fearsome pressure!
    That does indeed make my 6 to 7 bar look a bit pedestrian by comparison.
    And you're also completely right in that I am a bit of an old woman when it comes to these things. Of course if I hadn't fitted the guage I'd have been none the wiser and everything would have been fine.
    I guess that's one of the perils of perfectionism. ;)

    Thanks for your thoughts chaps. Much appreciated as ever.

  5. G Brown

    G Brown New Member

    7 bar is fine but I would fit a prv on the mians set at 3 bar. Not for 'safety' reasons just to stop noise as DA says.

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