pressure reducing valve effect on flow

Discussion in 'Plumbers' Talk' started by Craig88, Oct 24, 2017.

  1. Craig88

    Craig88 New Member


    When we bought our house the tap in the bathroom made quite a loud noise when turned on, both hot and cold. We replaced the tap and still have the same problem. I'm looking to install a PRV after the stop tap, but I am wondering if it will have a negative effect on the flow of the shower (mixer)?
  2. andy48

    andy48 Active Member

    1. You need to measure the pressure first, as it may already be too low to make a PRV effective.
    2. Which tap? Basin, bath, other?
    3. What sort of noise? Banging, rattling, hissing?
    4. If you reduce the water pressure, it may reduce the flow from the shower.
  3. Craig88

    Craig88 New Member

    How can I measure the pressure?

    Basin taps are what have the issue, no other taps seem to do it.

    It’s like a humming noise, no banging. If I turn the isolation valve down it helps a bit but it’s still doing it.
  4. Craig88

    Craig88 New Member

    I finally got round to installing a PRV after the stop tap, and it did fix the issue with the taps but it reduced my shower flow to much.

    Any other ideas? I can attach the gauge to the PRV to get the pressure if thats helpful.
  5. The Teach

    The Teach Well-Known Member

  6. Craig88

    Craig88 New Member

    I already have isolating valves for each tap supply under the sink. Turning this down helps, but I end up with just a trickle of water if I turn it down enough to eliminate the noise. Do you think the aerator would work? I may try it as it could be a cheap fix. I'm not sure if its compatible but the taps do currently have a small screw in aerator so it may well be.
  7. Pollowick

    Pollowick Well-Known Member

  8. The Teach

    The Teach Well-Known Member

    Fair point,isolation valves will slow the water flow but not the initial spurt of water.they are an on/off product.The isolation valve will restrict the flow in a way but can create velocity reduction noise.

    Can you remove the existing aerator and measure the thread,they are adjustable and a cheap option but need periodic cleaning.

    The calflow product is a professional option,they work very well where the flow needs to be controlled. have fitted 100's of them in hotels b&b's
  9. Craig88

    Craig88 New Member

    I'll try and measure it tonight. If the calfow product would work then I may purchase one and try it. I thought I needed something to reduce pressure, the calflow product appears to reduce flow? Do you think this would resolve the issue still?

    The noise is like a screeching, almost like a vibration that is causing the tap to make a noise. If I feel along any accessible pipe work though there isn’t a vibration that I can feel or stop.

    The PRV I did fit is this -

    And it did appear to resolve the problem, except it then affected my shower. Plus I don't really have room to move this to under the sink without it being on show, thats why I fitted it after the stop tap.
  10. The Teach

    The Teach Well-Known Member

    both of the products in #5 reduce flow by creating a pressure barrier.they work on a constant flow idea .

    the idea is to be able to turn the tap on full and not get splash over and noise via metal tap restrictions. look at the sf product online it could have replaced for a newer part but buy on line and return it if it does not work.

    Basins only need 4 ish lpm on the mixer tap spout.

    Adjust it to suit your requirements,they work but your existing plumbing will need to be already correctly installed and up to code.

    I fit the calflow products to reduce basin,sink,wc,dishwasher, wm flow so the shower's get priority water constant flow,making for a better shower experience :)
    Craig88 likes this.
  11. Craig88

    Craig88 New Member

  12. Hi Craig.

    I had the exact same issue with a fancy 'waterfall-type tap I fitted on an en-suit basin - what a racket.

    Like you I found that tweaking down the isolators didn't work until they were nearly off. Like you I fitted a PRV on the mains and tweaked it down to 3 bar. Like you I found it helped the noise, but did also affect the flow to things like the garden hose etc where I wanted a strong jet of water, and also the shower wouldn't be as powerful when full on.

    I was lucky in that the problem resolved itself - the tap broke and I replaced it with a normal one.

    I hope that helps.


    I was going to suggest moving the PRVs to supply only that tap, but I see you've mentioned that they'd be too visible. I think this would have been the 'guaranteed' decision - no chance of fitting them further down the line?

    Failing that, although I have had no experience of them, I can only suggest trying Teach's Calflow regulator - tho' I don't fully understand the difference between it and a high-quality ball valve. You may find an acceptable balance between tweaking these Calflows down whilst being able to tweak the PRV you've fitted back up a bit. Ie, restoring acceptable flow rate to the rest of your house by increasing the PRV setting, whilst reducing the tap noise by enough tweaking down the Calflow; 'balancing' these two products.
  13. Pollowick

    Pollowick Well-Known Member

    You obviusly have not looked or even checked the link provided. The one you have is a NEOPERL - it says on the tool. Doing the work for you, brings up:

    with several flow rates available.
    Deleted member 33931 likes this.

    Craig88 likes this.
  15. Dr Bodgit

    Dr Bodgit Well-Known Member

    Isolators are carp for reducing flow/pressure as you say, better are gate valves...which I fitted to my new waterfall mixer tap but then found out I don't need as the tap is min 0.5 bar on a 0.2 bar setup :oops:
  16. Not sure a gate valve would be any better in such a situation as all it can do is reduce flow - it's the force behind this flow, the pressure, wot causes the racket.
    Craig88 likes this.
  17. Dr Bodgit

    Dr Bodgit Well-Known Member

    Yes it would, not sure how much.

    The way isolators work means that the "hole" is pretty much fully open until the valve is darn near fully shut. A gate valve has a more linear closing effect so when half shut it is actually shutting off about half the area of the pipe.
    Craig88 and Deleted member 33931 like this.
  18. Dave does Gas

    Dave does Gas Well-Known Member

    It will also increase the noise as the water passes at the same pressure through a smaller aperture whereas a PRV is spring loaded to prevent this very issue. All your doing by fitting a gate valve or partially closing a ballofix valve is reducing the flow not the pressure which is the very reason Pressure reducing valves were invented.
    Craig88 likes this.
  19. Wayners

    Wayners Well-Known Member

    Should you have not fitted a water hammer arrestor to stop the bang?
  20. Craig88

    Craig88 New Member

    There isn't a bang, more of a constant screeching noise when the tap is open.

Share This Page