Noise coming from meter/PRV area

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by homemade plumber, Oct 25, 2009.

  1. homemade plumber

    homemade plumber New Member

    Messages:
    4
    Location:
    CT
    I am hearing a noise coming from the area of my main water line near the meter and a PRV installed just after it. The noise is a humming vibration with a pulsing "thump" also. It only happens when the water is running (toilets or sinks) and stops when the water is shut off. I have minor plumbing skills but I don't know too much when it comes to meters or pressure regulating valves, so I am not sure where to start.
    What should I check first?
    The PRV looks pretty old. Could that need to be replaced or adjusted?
    What are the chances the meter itself is bad?

    Any advice is appreciated
  2. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    It's probably the PRV but it may be the meter. Try the old screwdrive handle in your ear trick on both the PRV and the meter with the water running. See which is louder.
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,824
    Location:
    New England
    PRV's don't last forever. While you can buy rebuild kits for some of them, it is often quicker/easier to just replace it. Do you have an expansion tank? If not, you need one with the PRV. It could also be waterlogged or the pressure is low.
  4. homemade plumber

    homemade plumber New Member

    Messages:
    4
    Location:
    CT
    I don't see an expansion tank in the area, so I am pretty sure I don't have one. How important is that? If I am going to replace the PRV anyway, should I add one in?

    What is the proper pressure for the home anyway? I have done minor work on residential plumbing in the past but never had to worry about the pressure.
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,824
    Location:
    New England
    A PRV and an expansion tank go hand-in-hand...if you have a prv, you need the other. So, yes, add one.

    Home pressure is somewhat a personal preference, but 50-60# is normally fine for most people. It just shouldn't be above 80#.

    If you don't have an expansion tank, and you've not had problems, your PRV is probably not doing its function. A PRV acts as a one-way valve. WHen you use hot water from the tank, then refill it with cold, when it expands, it has nowhere to go except to leak or push back to the street. It shouldn't leak back (note some are designed to allow that but your internal pressure could get quite high before that happens - the internal pressure must exceed the street, and that could be too high).
  6. homemade plumber

    homemade plumber New Member

    Messages:
    4
    Location:
    CT
    I don't actually have a hot water tank, I have tankless hot water through my heating system. Could this be the reason there is no expansion tank?
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,824
    Location:
    New England
    Probably...not sure about the code issues...I'm not sure they've accounted for that type of heater. If you ever replace it with a tank, you must have an expansion tank to go along with it. It wouldn't hurt to install one, but it probably won't buy you much of anything. Interesting to see what the code and the pros have to say.
  8. Doherty Plumbing

    Doherty Plumbing Journeyman & Gas Fitter

    Messages:
    810
    Location:
    Penticton, BC
    It is interesting to me that's it's code you have an expansion tank on your systems. Up here in BC where I am from this isn't a code requirement and is hardly ever done.

    To me the access pressure created by the HWT and it's thermal expansion would only further close the PRV. Not force the water back into the city main. PRV's close on down stream pressure not up stream pressure. So if your system is set to run @ 60 psi and you suddenly jack that pressure up to 100 psi that extra pressure should just close the prv even tighter.

    Sometimes I need to install one for a customer if their HWT constantly causes thermal expansion to trip the relief valve but this is rare. And is mostly on gas HWT vs electric tanks.

    It's interesting to see all the differences in our code!
  9. Salesdog

    Salesdog New Member

    Messages:
    15
    Location:
    British Columbia
    I am also from BC, and in most municipalities that I have worked in, we are required to put a dual check valve on the water entry which moots the whole point of water expansion back into the city. it actually was required to protect the city water supply in the case of legionella flowing back into the city mains afaik. Its well known that us Canadians seem to be a little over cautious about legionella though...

    Though I do agree an expansion tank seems a bit overkill, usually there is enough wiggle room in the system to accommodate thermal expansion, unless there is a recirculation system installed with check valves so the hot cannot expand into the cold water lines, then yes the TnP will always trip and a expansion tank is necessary.
  10. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    An expansion tank prevents pressure build up and fluctuation which can shorten the life of a water heater and affect fixtures...if the pressure gets high enough it will cause the T&P to open...
  11. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,304
    Location:
    Cave Creek, Arizona
    noise

    The noise is probably from the PRV, and if you used a gauge to test the pressure, you would probably find that it drops considerably when a faucet is opened. A tankless heater does not need an expansion tank because it is only heating when a faucet is opened, and a coil type tankless does not have enough water to create a thermal expansion pressure increase.
  12. Doherty Plumbing

    Doherty Plumbing Journeyman & Gas Fitter

    Messages:
    810
    Location:
    Penticton, BC
    Yeah where I am from they are going BIG on backflow prevention now. We get TONS of business because of it!!!
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