Banging pipes close to water heater when flushing any toilet

Discussion in 'General Plumbing Help' started by GaryAK, Jul 13, 2019.

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  1. Jul 13, 2019 #1

    GaryAK

    GaryAK

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    About one year ago a banging (hammering?) started occurring in the piping near the water heater when flusing any of three toilets in the house. The banging continues until the toilet tank is filled. The banging does not occur when opening and closing any other valve or faucet in the house. The system does have a pressure regulation valve and expansion tank. I have followed instructions to turn off main and drain all piping in the house. This has not corrected the issue. I am totally confused at to why this occurs only when any of the 3 toilets are running and only when one of the 3 toilets is running. Any help would be appreciated. What should be my next step? Replace expansion tank? Replace Pressure control valve? Replace ALL? toilet float valve?

    GaryAK
     
  2. Jul 13, 2019 #2

    havasu

    havasu

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    A quick, easy solution would be to shut down your main water line. Turn off your incoming cold water on the water heater. Drain all the water out of the pipes, and flush the toilets. When lines are empty, open up the main water line and let everything fill. What this does is create air pockets to relieve the water hammer affect. It is a simple, often successful way to rid your plumbing from the water hammer sounds.
     
  3. Jul 13, 2019 #3

    GaryAK

    GaryAK

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    As I mentioned in my post, I have done this but it did not help
     
  4. Jul 13, 2019 #4

    havasu

    havasu

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    Sorry, I should pay attention closer to posts. What exactly is your incoming water pressure? Often, regulators go wonky. And this is an easy way to confirm if it has gone bad. Thread on a pressure gauge onto your spigot and see what it reads.
     
  5. Jul 13, 2019 #5

    GaryAK

    GaryAK

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    Thanks for the responses
    I will need to purchase a gauge. You mention connect it to a spigot, from this I guess it does not matter where in the system I connect the gauge. I see there are gauges with varying connections. Can you recommend a particular gauge? I will probably order it from Amazon. I have thought about checking pressure on the expansion tank also, is the a gauge that can do both?

    Thanks again for you help
     
  6. Jul 14, 2019 #6

    jeffmattero76

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    You can buy from Amazon, but it might be quicker to walk into a big box or hardware store. They sell for less than $10. Mine hooks to my hose bibb or laundry tub faucet.
     
  7. Jul 14, 2019 #7

    havasu

    havasu

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    This one is $12.59 at Home Depot. I'm sure Amazon water-source-pressure-test-gauges-wspgh100-64_400_compressed.jpg will have similar.
     
  8. Jul 14, 2019 #8

    GaryAK

    GaryAK

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    Thanks again for your help. I purchased a pressure gauge at Home Depot for $10 I have connected it to the hot water heater drain connection and it reads 80 psi. According to the info on the gauge instructions it says if pressure is over 60 psi to install an expansion tank. My system already has an expansion tank (wondering it that is the problem). Also system has a pressure regulator valve (see attached pic). The tag says range 25 to 75 psi. Does this mean the regulator is bad? It also looks like there is a screw adjustment on the regulator, I have not attempted to turn this but I am wondering if that allows for adjustment to the pressure in the system.
     

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  9. Jul 14, 2019 #9

    Rossando

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    The PRV valve should have a hose bib close by test after the prv valve and test before. Sounds like the valve is shot.
     
  10. Jul 15, 2019 #10

    havasu

    havasu

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    Do not put it on the water heater. Your numbers will be way off. Find a spigot.
     
  11. Jul 15, 2019 #11

    jeffmattero76

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    I don't own one, but I believe that the PRV is adjustable. Hence the range description on the metal tag that says 25 -75. I believe you would like your pressure to be around 50 psi.

    I would suggest attaching the gauge to your hose bibb or laundry tub, and then try to adjust the pressure.
     
  12. Jul 15, 2019 #12

    Diehard

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    Typically, high water pressure is not the direct cause of water hammer but rather amplifies it?
    Based on the description, that the sounds are occurring WHILE water is flowing, it sounds like the velocities changes(causes of water hammer) may be caused by things like a loose washer or closure device, air, foreign matter affecting flow, etc.
    It would still be a good idea to check that the PRV is functioning properly and that the expansion is set with the proper air pressure. Even though we are dealing with the cold water flow causing the problem.
     
  13. Jul 15, 2019 #13

    street

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    I have had a similar problem which was successfully resolved by turning down the toilet isolator tap just a little so that the water pressure into the cistern is reduced.
    Cost is zero. Good Luck
     
  14. Jul 15, 2019 #14

    GaryAK

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    I tried this, it had zero effect.
     
  15. Jul 15, 2019 #15

    GaryAK

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    Yes, this occurs ONLY when any of the three toilets are filling; as soon as the tank is full the hammering stops. It appears that the PRV is not functioning. I have cranked the adjustment from min to max and the pressure remains at 80 psi with all faucets and valves closed. I also notice that while the toilet is running the pressure is jumping from 40 to 50 psi. Don't think the inoperative PRV would cause this. Still very confused as to why this occurs ONLY when toilets run and not when any other value is opened. It seems that the float valve in the toilets is opening and closing as it runs. I notice that all three toilets do have the identical float valves. Thoughts?
     
  16. Jul 15, 2019 #16

    GaryAK

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    Did this, getting same readings at the hose bib as at the water heater.
     
  17. Jul 15, 2019 #17

    GaryAK

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    Is it the general consensus that since this is a cold water hammer the expansion tank is out of the equation? I suspect the expansion tank may be full of water, I can detect no difference in sound when tapping the bottom or top of the tank.
     
  18. Jul 15, 2019 #18

    gagecalman

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    I had a similar noise. It was the loudest when the toilets were filling but I could hear it just a little when a faucet was fully opened. It turned out to be the meter. I called the city and they removed it and put in a fitting that takes the place of the meter. All the noise was completely gone. They came back and installed a new meter and still no noise. It's been a while but it is starting to make noise again. I guess nothing last forever.
     
  19. Jul 15, 2019 #19

    GaryAK

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    Our meter is 100 feet from the house under ground at the curb. Don't think the noise would travel that far under ground. I can feel the hammering in the 1/2 inch copper pipe at the water heater.
     
  20. Jul 15, 2019 #20

    gagecalman

    gagecalman

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    Mine is about 50'. I have copper pipe and the noise must transfer along it. Just a thought.
     

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