Watts PRV Howls on start and stop of flow

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by CoHotelier, Aug 29, 2017.

  1. CoHotelier

    CoHotelier New Member

    Joined:
    Mar 22, 2016
    Location:
    Colorado
    Symptom:

    The prv (Watts LF25aub 1”) howls or sings loudly when it’s opening and closing, but not during the flow event (toilet, shower, doesn’t matter). If I throttle down flow at a hose bib, I can get it to howl/resonate continuously at very low flow.


    System Details:

    The building has 4 rooms, each with sink/tub/shower/lav. It is a standalone addition to our motel, so quite often two or three - and potentially four sets of fixtures could be running at once.

    Incoming town line pressure is 175psi as shown on our nearby fire system gauge on a dedicated 2” line. Domestic 1” Ts off of that line outside of the building.

    The incoming domestic line is 1” with a 1” Watts LF25aub PRV followed by a Watts Reduced Pressure Backflow Preventer.

    I’ve had the PRV open, no obvious defects, and screen isn’t clogged at all.

    Grabbing, adding mass, tension, etc to the PRV makes no difference

    I did add an expansion tank on the system near the domestic hot water heater to remove any home-side back pressure concerns, however I don’t think internal line pressure from expansion is a problem as the PRV is noisy on both opening and closing… I don’t see how line pressure build up from heated water would act fast enough to cause a problem on close, or after a full flow event… plus it’s all behind a backflow device.

    Adjusting pressure up and down seems to have an erratic, but not reliable effect. If I crank the pressure up I can get it quieter, but not silent, and not reliably quiet. Even at near 80psi it can still be noisy, it’s erractic.


    I’ve got a couple potential reasons this is happening as I see it…
    1. Outside pressure at 175psi throttled down to 60psi is too big of a drop at very low flow conditions (opening and closing) for the prv.
    2. The PRV is oversized at 1” for the four bedroom unit and is outside of its ideal operating conditions trying to handle high pressure and very low flow.
    3. The PRV is faulty (it’s six months old, but the noise started immediately upon install).

    Solutions are…
    1. Buy a rebuilt kit for $50 and see if that fixes it.
    2. Replace it with a new same unit, Watts 1” (Logic being even I used a rebuilt kid there could be something wrong with the hard parts or the cast of the original unit that a rebuilt kit wouldn’t address and it’d be a wasted $50 and time). Same unit would ease install effort.
    3. Replace it with a new same brand/model lf25aub unit, but in ¾” instead of 1”. A little repiping but nothing crazy.
    4. Replace it with a different brand 1” (I had looked at the 1” Caleffi 535 series with gauge, but not sure it’s right for my application).

    Thanks all for any attention you can give this.
     
    Last edited: Aug 29, 2017
  2. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    You could see if changing the regulation pressure helps. If you keep the change, change the thermal expansion tank air precharge to match or be just a tad more.

    Also consider calling Watts to see what they say. There is a 1 year warranty, and I suspect they will send the rebuild kit free. http://www.watts.com/pages/_products_details.asp?pid=6805#warranty I am not a pro.
     
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  4. CoHotelier

    CoHotelier New Member

    Joined:
    Mar 22, 2016
    Location:
    Colorado
    I appreciate that. I sent a note over to Watts, will update.

    I've attempted to manipulate pressure anywhere from 75psi down to 50 and there is no consistent impact. If I throttle it up, it will get quiet for a bit of use, but then the noise will return a bit later. The system is currently set to 60psi.
     
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    What is the max on that PRV? Some do not like that great of a pressure difference, and in those cases, they recommend dropping the pressure in stages with 2 PRVs in series...drop a bit in each one until you get the needed result.
     
  6. CoHotelier

    CoHotelier New Member

    Joined:
    Mar 22, 2016
    Location:
    Colorado
    Hey Jim, It's listed as up to 300psi max, so the 175 is probably higher than 90% of their domestic installs, but is within their stated range.
     
    Last edited: Aug 29, 2017
  7. CoHotelier

    CoHotelier New Member

    Joined:
    Mar 22, 2016
    Location:
    Colorado
    Heard back from Watts, the initial thought is that even though the unit is rated to 300psi, it is likely a problem with incoming line pressure. They recommended buying a High Pressure variant and putting it in series with the PRV I have, using the one to step down some, and then the next one to step down the rest of the way.

    I reached out to Caleffi to see if they have input on if their unit would be any better. If I'm going to have to spend the $150-$200 on another PRV and rework the input, I may as well see if another model would do it all in one.
     
  8. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    That is a disappointing reaction. Has the howling been there from the beginning?

    There is a cleanable screen on your PRV. I can't think that would help your howling, but it might be worth a look.
     
  9. CoHotelier

    CoHotelier New Member

    Joined:
    Mar 22, 2016
    Location:
    Colorado
    I agree!

    Yes, from day 1. When I disassembled the PRV to check the internals, I gave it all a once over. The screen was clear, and I couldn't find any obvious defects with the diaphragm, etc.

    When I let the plumber (a subcontractor) know about the howling issue, he came back out and tweaked with the setting for a bit, eventually setting it on the high side (like 75psi) because it seemed to stop the problem. The issue returned shortly thereafter, and I haven't bothered to call them back. This was a project we needed to have a sub do the work on, but if I need to retrofit or replace anything, I have the ability and it'll be immensely cheaper, for both parts and labor, to do it myself.
     
  10. dj2

    dj2 In the Trades

    Joined:
    Aug 13, 2013
    Location:
    California
    Such a noise would bother me too.

    Replace the PRV with a 1" Wilkins Zurn. They are the very popular around here, and write it off as a repair.
     
  11. CoHotelier

    CoHotelier New Member

    Joined:
    Mar 22, 2016
    Location:
    Colorado
    Hey DJ2, thanks for the input. I've got a 3/4" Zurn on my irrigation line and it's silent and seems reliable. I researched PRVs from Watts, Caleffi, and Zurn - and in a few places I found folks talk about a very high psi drop across the valve, so I had shied away from them as a reasonable replacement. I'll give them another look.
     
  12. CoHotelier

    CoHotelier New Member

    Joined:
    Mar 22, 2016
    Location:
    Colorado
    Just an update. I emailed back and forth with Caleffi a few times and am going to give their valve a try. I appreciate the insight here - both from a set of valves in series, and disappointment that "well, just buy another one to make this one work" was the proposed solution.

    Their (Callefi's) insight was that the valve should operate within spec without the need for piggybacking another valve. In this case, 180 to 65psi shouldn't be too much to ask for a valve listed as operating within 0-300psi. No promises of silence, but worth a shot.

    I've got the Zurn 1" in my "cart" so to speak, for about $50, so if the Caleffi doesn't do it, I'll give the Zurn a go.

    If neither, then a set of series valves will be the last resort.

    I'll update once the Caleffi is in for a bit of time and hopefully this will help someone in the future.
     
  13. valveman

    valveman Cary Austin Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    High differential pressure across the seat causes the howling. You maybe able to find a reduced cavitation type valve that will handle the high differential better, but they are not cheap. Probably do not need a special valve for this, just another like the one you have with an adjustment up to maybe 100-125 PSI. First valve takes it down from 175 to 100 PSI. The second valve would see the 100 and take it down to 65 as needed. Splits the differential pressure in half. Even if you find a high pressure anti-cav valve, the high differential pressure will eat the seat off quicker than normal. I think splitting the pressure between two valves is the best thing to do.
     
  14. CoHotelier

    CoHotelier New Member

    Joined:
    Mar 22, 2016
    Location:
    Colorado
    Valveman, am I wasting my time, then, trying the Caleffi 535 series valve? When you say shortening the lifespan of the wear parts of the valve, can you ballpark that impact? Are we talking halving the lifespan?
     
  15. valveman

    valveman Cary Austin Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    It depends on how often and/or how long you use water at low flow rates, like when it makes the noise. From the ones I have used that worked at low flow 24/7, sometimes you don't even get 6 months before the seat is worn off. But 6 months worth of low flow at 5 minutes a day actual use could take a long time to wear it out. It probably won't be long, months maybe years, before the valve starts leaking past the seat. This will let the pressure equalize when no flow is being used. Then you will either have high pressure in the house, or need to use a pressure relief to dump the amount the pressure reducing valve is leaking.
     
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