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Thread: Pressure OK, but water volume low

  1. #1

    Default Pressure OK, but water volume low

    When the washing machine is filling, the water flow at the kitchen sink and other faucets is pretty low. Is this normal?

    We have a Watts 135BM3 PRV near the water meter, no expansion tank. The pressure prior to the PRV is 120 lbs, and the pressure in the house is 65-75 lbs.

    A plumber (here for a different problem) told me that there's a screen in the Watts PRV that is probably clogged, if pressure is good but volume is not. Does this sound correct?

    The PRV has been there for at least 25 years, maybe longer. Should it be rebuilt or cleaned?

  2. #2
    Master Plumber Redwood's Avatar
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    The screen at the PRV is a good thing to check 1st.

  3. #3

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    Thanks. Will I need a gasket? If so, is that a Home Depot item or plumbing shop?

  4. #4
    Senior Robin Hood Guy Ian Gills's Avatar
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    I would first of all check your pipes. Is it 1/2 inch pipe servicing that washer, the kitchen sink and the other faucets or 3/4 inch.

    If it is the former, it might be too narrow pipe servicing too many fixtures.

    Has this always happened or just recently??
    Last edited by Ian Gills; 08-04-2008 at 12:50 PM.

  5. #5
    Forum Admin, Expert Plumber Terry's Avatar
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    All fixtures like kitchens and washers are piped in 1/2"
    Many supplies are 3/8" which is plenty.
    If you are having a pressure drop off, it's like what Redwood is saying.
    It's the PRV
    I see this happen a lot.
    Last edited by Terry; 08-04-2008 at 01:11 PM.

  6. #6
    Senior Robin Hood Guy Ian Gills's Avatar
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    Apologies, I should have been clearer.

    http://www.terrylove.com/watersize.htm

    I run a washer, a kitchen faucet, a dishwasher, a garden faucet and a utility sink off of 1/2 inch pipe. I shouldn't but it does not cause us any problems because there are only two of us in the house and we never use all of these things at the same time.

    If we did, then it would cause problems because the pipe servicing these fixtures is undersized.

    If your low flow has always been like that, it may not be the PRV. Just one possibility depending on how many fixtures you have and your pipe size.
    Last edited by Ian Gills; 08-04-2008 at 01:17 PM.

  7. #7
    Forum Admin, Expert Plumber Terry's Avatar
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    But likely the house was plumbed to code, and inspected.
    And if the house is only 25 years old, then it's copper pipe.
    It ain't the pipes.

    Check the PRV valve.
    I've been a commercial plumber for thirty years, and before that a residential plumber.

  8. #8

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    This isn't a new problem. I didn't even realize it could possibly be improved until that plumber commented about it.

    The house is old, built in 1914.

    Piping from meter to PVR, and about 4 ft beyond, is 3/4" copper. Beyond that its 1/2" galvanized.

    There are only two of us in the family and the flow issue is only a "problem" when the washer is filling. Washer is about 10 ft. from the PVR. The one and only bath is 25 ft., and the kitchen is maybe 45 ft. down the line.

    If all it takes is a screen cleaning I'm up for it. But I'd like to have parts in hand before disrupting water to the entire house.

  9. #9
    In the Trades Gary Swart's Avatar
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    My money is on the inside of the galvanized pipe being corroded to a fraction of normal size. I would venture a guess that when that is cleared up and the PRV is cleaned out and operating properly, the T&P valve on the water heater will trip. You will need a thermal expansion tank. I can't explain why it hasn't caused problems before.

  10. #10

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    The galvanized may indeed be restricted, but the water heater isn't preceded by any galvanized. Water flows from the Copper near the PVR, through a run of Pex to and from the water heater, and then connects to the galvanized.

    So, how do you "clear up" the galvanized pipe corrosion? Replacement, right?

  11. #11
    Forum Admin, Expert Plumber Terry's Avatar
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    The house is old, built in 1914.
    Well that sounds older than 25 years.
    It still may be the PRV, They can slow down.
    Some plumbers just replace them if parts can't be had.
    That is the easiest step without pipe replacement.
    Normally you could come in with 3/4" for a one bath home.
    I don't put more than two plumbing fixtures on 1/2".
    That would mean running 3/4" on the cold side to the bathroom, and 1/2" for the lav and tub.

  12. #12

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    Replacing the PRV... Hmmm... looks like a $200 part. I'll have to call around for a gasket, and then take it apart for a look.

    I saw mention of an expansion tank. Is that necessary? What difference would it make?

    In case it matters (mentioning here because I saw brief mention in another thread):
    I have a recirculation pump at the water heater. Pulls hot water from the kitchen (furthest point), back to the water heater via Pex pipe.

    The PRV has seemingly worked fine for years... I hope I find the screen clogged, but would like to improve the system if its needed.

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