Banging when opening/closing faucet...

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by cool5abi, Dec 28, 2011.

  1. cool5abi

    cool5abi New Member

    Messages:
    6
    Location:
    Ontario
    Hello All,

    I'm super stumped with a problem I've been having with my plumbing for some time. The house is 11 years old (purchased new), and is city fed. I've been hearing the noise for several months now, but only now has it become worrisome (it was very faint and hardly ever happened in the beginning).

    Essentially, when opening or closing any faucet (hot or cold) in the house I hear considerable banging from my pipes. In some faucets (second floor baths) I can even feel a knock from the handle of the faucet when the banging occurs. The noise seems to be loudest just a bit away from a shower/bathtub in the second floor bath, I believe the banging can be felt in the floor as well. I've done the following so far;


    1. Made sure all pipes were tight and secure.
    2. Replaced the cartridge assembly for both showers.
    3. Replaced the seats for the lavatory faucets.
    4. Drained and refilled the pipes... a few times. (Hoping to fill the air chambers with air again).



    I'm familiar with the principle of water hammer, and I see how it occurs when suddenly stopping the flow of water. But I can't seem to figure out why the pipes would bang when opening the faucet as well. I've opened up the drywall below the tub and can't feel the pipes banging against the joists, so I believe the noise is caused by the water in the pipes themselves. Usually, you will hear 3-4 bangs, almost seems like water is flowing back and forth hitting something.

    Since the problem occurs when opening/closing both the hot and cold water, I decided to try one last thing... turn off the supply to the hot water tank. Strangely enough, the banging no longer occurs... What could cause this?
  2. Terry

    Terry Administrator Staff Member

    Messages:
    15,044
    Location:
    Bothell, Washington
    I would check the pipe nipples going into the water heater.
    Sometimes there is a small ball that acts as a heat trap, and they can go bad.

    If you replace them, and you are using flex connectors, either change the rubber washer at the end, or replace the flex.

    How about posting a picture of the top of the water heater and it's connections?
    Last edited: Dec 29, 2011
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,684
    Location:
    Cave Creek, Arizona
    The bang when a faucet is opened is called "reverse water hammer". It occurs when the faucet is opened quickly, but the inertia of the water in the pipes doesn't allow it to start moving immediately. This causes a momentary drop in pressure to ZERO psi, and then when the water does start to move it moves rapidly, but then "rams" the water ahead of it in the pipe, (often increasing the pressure beyond the hundred plus range), causing the bang. It is usually caused by a very long, often small, pipe. The cure is to install an "accumulator tank", such as an expansion tank in the piping near the offending faucets. The air cushion in the tank will maintain the pressure until the water can overcome the inertia, thus eliminating the shock.
  4. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    4,003
    Location:
    NW Ontario, Canada
    I'm guessing since it affects both hot and cold, that it may be from a pressure regulator that's getting a little sticky.
  5. cool5abi

    cool5abi New Member

    Messages:
    6
    Location:
    Ontario
    I doubled checked the HWT, I simply have my 1/2" copper with a female threaded fitting screwing straight into the tank. I don't believe there is any place where a ball or other type of check valve would be located.
  6. cool5abi

    cool5abi New Member

    Messages:
    6
    Location:
    Ontario
    Reverse water hammer does sound the most descriptive, but what would cause this to happen when everything has been fine for the previous 10 years; it's not like I've always suffered from this issue. Either when opening or closing the faucets, I get multiple bangs (between 2-4) almost sounds like either the pipe is loose or the water is banging back and forth in the pipes. Just to make things more difficult, it's not one offending faucet; it's essentially all of them and they get worse as you go higher up in the house.
  7. cool5abi

    cool5abi New Member

    Messages:
    6
    Location:
    Ontario

    Well, we never had a pressure regulator, in fact they're not very common in Toronto. If it was simply high supply pressure causing water hammer, it doesn't explain why it stops when I turn off the supply to the HWT.

    With the supply to the HWT turned on, I get banging on both hot and cold. With the supply to the HWT turned off, I get some banging on the cold side, if I turn toward hot a little bit of water will dribble out (as it should) but once I go back to the cold all is silent. At that point, no matter how often or how quickly I turn any of the faucets on/off; there is no noise.
  8. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    4,003
    Location:
    NW Ontario, Canada
    Sorry, I missed the bit about turning off the HWT supply. In that case Terry is spot on. Your HWT has heat traps built into the nipples. Get someone to turn the taps on and off while you stand at the water heater with your hands on the nipples and you should feel the clunking. I've been tempted to remove the heat traps on mine.
  9. Smooky

    Smooky Member

    Messages:
    623
    Location:
    NC
    Make sure all the shutoff valves under the sinks etc are all the way open.
  10. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,684
    Location:
    Cave Creek, Arizona
    Since the sound is caused by a flow problem, it is something which CAN develop suddenly. EVERY water hammer, regardless of the cause, produces MANY "bangs" because the shock wave oscillates back and forth. Whether you hear the multiple sounds depends on their frequency and volume.
  11. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    As you say, SOMETHING has changed. One of the things which MIGHT have changed is your pressure. It is a simple matter to test it, and then you can check off one more thing on the list of possibities ( OR you might have FOUND the problem!!)
  12. cool5abi

    cool5abi New Member

    Messages:
    6
    Location:
    Ontario
    All things do seem to be pointing to the HWT; I do have short nipples on my HWT but they seem too short to be heat traps...http://www.flickr.com/photos/birdi/6601668129/sizes/z/in/photostream/Although I can't feel any clunking, I do hear some slight "metallic" like sounds when the water turns on/off. It sounds like bits of metal or marbles are hitting each other in/near the HWT.

    Attached Files:

    Last edited by a moderator: Dec 30, 2011
  13. Terry

    Terry Administrator Staff Member

    Messages:
    15,044
    Location:
    Bothell, Washington
    Those could have the floating ball in them. Without pulling the pipe off the end, it's hard to say. You may want to have someone run the water and put your ear close and listen for it.
  14. Pipewrench

    Pipewrench In the Trades

    Messages:
    37
    Location:
    Jackson MS
    You got a bad angle stop somewhere
  15. cool5abi

    cool5abi New Member

    Messages:
    6
    Location:
    Ontario
    I doubt it, I get the noise on both hot and cold sides; the moment I turn off the water supply to the HWT all the noise is gone. I can close all the angle stops in the house and it makes no difference.

    I'm going to try and change the heat traps as suggested, everything seems to be pointing to the HWT. I'm also going to try and get my hands on a water pressure gauge, it would be nice to know exactly what the water pressure is in my house.
  16. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,684
    Location:
    Cave Creek, Arizona
    You may not have to change the nipples but, rather, pop the heat traps out of them.
  17. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    4,003
    Location:
    NW Ontario, Canada
    +1

    I suspect new ones would make the same noise. Mine have been making that noise from day 1.

    It's because now and then tank sediment gets up into them and they get sticky that I'm considering removing them. Laziness has prevented me cuz there are no unions so I would have to cut or unsweat the pipes to get at them.
  18. spinn

    spinn New Member

    Messages:
    1
    Location:
    Toronto
    Was this problem ever resolved? I have the exact same problem that no one can find a solution to. Banging / knocking noise directly behind the bath valve of new install at second floor bath. The noise occurs whenever any faucet in the house is turned on or off or when washer, dishwasher, toilet runs.

    The sound is definitely behind the bath valve and it is not pipes banging as I can touch and see the pipes through the rough-in attic space behind the bathroom.

    There are shock arrestors on both the hot and cold pipe and I have tried flushing the system in several different ways.

    Also, the noise stops when the the supply to the new tankless hot water heater is turned off. THe noise started before the tankless was installed though.

    I thought maybe it was a faulty bath valve but since you replaced your cartridges and the noise persisted....I don't know.

    Any further suggestions?
  19. Jcvancouver

    Jcvancouver New Member

    Messages:
    1
    Location:
    British Columbia
    I know it's an old thread but I had the exact same problem as OP and previous poster. I had banging noises coming from behind the bathtub faucets. Any tap turned on or off in the house would cause the banging, hot or cold. I have one handle faucets for the tubs in both bathrooms.

    I narrowed the noise down to the bathtub faucets by removing the hardware and closing the feeder screws. Completely closing both feeder screws would eliminated the noises, varying degrees of open would stop the banging for a while but the noises would come back after a bit of use.

    I removed the cartridge, disassembled, cleaned, and put it back in (seals and rings seemed fine). The noise Is now gone.

    From what I can gather, my cartridge has a metal bearing in it that controls the hot and cold water. This metal bearing that moves left and right and is the source of the banging. The pipes amplified the banging quite a bit and you wouldn't assume the cartridge is the culprit. The way my cartridge works is the metal bearing moves left to cover the hot water opening and moves right to cover the cold. When the bearing is in the middle it mixes and you get warm (obviously). When other taps in the house are turned on and off the effect of water hammer causes this bearing to slam left and right.

    By turning off the flow from the HWT, this bearing is constantly being pushed left as there is only pressure from the cold water so it would it would not move back and fourth anymore.

    If you can isolate the noise with the feeder screws, it's the cartridge. I have read in other posts that faucets made in different years have different cartridges even though the hardware looks the same. That might explain why OP still encountered the banging after replacing the cartridges. If not, good luck hunting and keep us posted.
    Last edited: Jan 22, 2013
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