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Boiler Pressure Relief Valve dripping

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neilmclneilmcl Forumite
16.9K posts
Part of the Furniture 10,000 Posts Name Dropper
My dad's Worcester Bosch Greenstar CDi combi was playing up recently where it the pressure was dropping below 1 bar on a regular basis and then, having once again topping it up, started to constantly increase pressure into the red. We had to draw off a good few litres to drop it back down to 1 bar.

Now it seems to remaining at a constant pressure but we've noticed that it's dripping from the pressure relief pipe outside, presumably the PRV had blown when it when into the red at some point. The boiler is a good few years old, possibly over 10 years, do we need a new PRV or is there an easy fix? Is there anything I can check before he needs to call out his plumber?


  • edited 12 January 2020 at 10:35PM
    JimmyChangaJimmyChanga Forumite
    262 posts
    edited 12 January 2020 at 10:35PM
    Usually the expansion vessel needs pumping up with air.

    The PRV may start leaking after it's deployed because the seal hasn't seated properly. Turn it a few times and that may resolve itself.
  • southcoastrgisouthcoastrgi Forumite
    6.2K posts
    Ninth Anniversary 1,000 Posts Name Dropper Photogenic
    Pump up the expansion vessel when he changes the prv
    I'm only here while I wait for Corrie to start.

    You get no BS from me & if I think you are wrong I WILL tell you.
  • The PRV will (or should) blow off at 3 bar, it's also known as (and will usually be stamped on it) the "3 bar valve" - as per a previous post, when they do blow off they do sometimes not "reset" properly, usually (in my humble experience) this is resolvable by just outright fiddling with it a bit. They will usually re-seat with a bit of assistance.
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