Do I need a new pressure reducing valve?

Discussion in 'Plumbers' Talk' started by Imajica, Apr 16, 2018.

  1. Imajica

    Imajica New Member


    I have a pressure reducing valve (Caleffi) which is about 12 yrs old and shows the inlet water pressure at about 3.8 bar.

    Water pressure in the house cold and hot (I have a combi boiler) is awful.... about 5L/min kitchen, cold and hot, and about 3L/min upstairs.

    The reducing valve seems to be set at max 5 bar, but adjusting seems to make no difference...

    Any advice greatly received - getting bored of waiting an hour for a bath !
  2. dcox

    dcox Active Member

    Do you know that the mains pressure before it gets to the reducing valve is more than 3.8 bar? That may well be the full mains pressure so changing the valve wouldn't make any difference.
  3. Imajica

    Imajica New Member

    Thanks for the response - No I've no idea, as the water meter is in line and immediately before the pressure reducing valve... does that flow rate sounds acceptable then, if the mains pressure is around 3.8 bar ? (looks like 15mm copper to the taps)
  4. dcox

    dcox Active Member

    Pressure sounds about right but your flow is poor, especially upstairs. Lots of threads on this forum about the difference between flow and pressure so I won't try to describe again. Do you have an unvented cyclinder to store your hot water? I'm wondering if that's why you have the valve fitted.
  5. Also, pressure and flow are separate things, although connected.

    It is quite possible to have water flowing under 5 bar pressure but only at 5 lpm (see the outlet of a pressure washer for an extreme example) tho' in a domestic water supply, you would expect a solid 3.8 bar pressure to be shoving a goodly 20+ lpm with it.

    Interesting that your cold taps also have a poor flow as this removes the combi boiler as the cause.

    So, since your PRV doesn't have any effect when adjusted, I would presume it to be the guilty party here; I'm guessing it's stuck partially closed (it has a 'piston' inside which moves to control the pressure).

    They are very dismantleable, tho' - fancy giving this a bash? Have a tub of silicone grease handy, undo the cover - it'll have a mesh filter inside - and then work out how to take the rest apart; I think there's essentially only one wee nut in the middle. Clean it up, remove all crustiness, and smear everything with sili grease - all metal and all rubber parts.

    Jobbie very likely jobbed.

    (Mind you, if your mains pressure is 'only' 3.8 bar, then you barely need a PRV.)
  6. Imajica

    Imajica New Member

    Thanks both... No, there is no cylinder - kind of wish there was ! Cold taps definitely have the same issue, and bath taps on mixed have the same flow so the water coming through the boiler and the cold fill are obviously sharing the available pressure.

    More than happy to dismantle it and give it a clean! Love a bit of dismantling! must remember to shut off the water supply first!
  7. rogerk101

    rogerk101 Well-Known Member

    I have dismantled a few but always ended up replacing the whole thing because the supposedly sealing surfaces were too pitted for it to be repairable.
    They're only about £20 and they certainly do have a limited lifespan.
    Frankly, if I had 3.8 bar mains, I wouldn't bother with a PRV at all. Where I live, the pressure is usually between 6 and 8 bar, which causes all sorts of challenges - hence my need to bring it all back down to 3 bar.
    Make sure you get the static one, as the dynamic ones only reduce pressure when water is flowing.
  8. Imajica

    Imajica New Member

    Cheers Roger - I guess the issue is I don't know if its 3.8 bar or not given the valve doesn't seem to work too well !

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