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Thread: Banging when opening/closing faucet...

  1. #1
    DIY Junior Member cool5abi's Avatar
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    Default Banging when opening/closing faucet...

    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. #2
    Forum Admin, Expert Plumber Terry's Avatar
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    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 by Terry; 12-29-2011 at 09:30 AM.

  3. #3
    Moderator & Master Plumber hj's Avatar
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    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.
    Licensed residential and commercial plumber

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    DIYer, not in the trades LLigetfa's Avatar
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    I'm guessing since it affects both hot and cold, that it may be from a pressure regulator that's getting a little sticky.

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    DIY Junior Member cool5abi's Avatar
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    Quote Originally Posted by Terry View Post
    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.
    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. #6
    DIY Junior Member cool5abi's Avatar
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    Quote Originally Posted by hj View Post
    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.
    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.

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    DIY Junior Member cool5abi's Avatar
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    Quote Originally Posted by LLigetfa View Post
    I'm guessing since it affects both hot and cold, that it may be from a pressure regulator that's getting a little sticky.

    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.

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    DIYer, not in the trades LLigetfa's Avatar
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    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.

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    DIY Senior Member Smooky's Avatar
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    Make sure all the shutoff valves under the sinks etc are all the way open.

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    Moderator & Master Plumber hj's Avatar
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    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.
    Licensed residential and commercial plumber

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    Plumber jimbo's Avatar
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    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. #12
    DIY Junior Member cool5abi's Avatar
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    Quote Originally Posted by LLigetfa View Post
    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.
    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/6...n/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 Images Attached Images  
    Last edited by Terry; 12-30-2011 at 11:43 AM.

  13. #13
    Forum Admin, Expert Plumber Terry's Avatar
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    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. #14
    In the Trades Pipewrench's Avatar
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    You got a bad angle stop somewhere

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    DIY Junior Member cool5abi's Avatar
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    Quote Originally Posted by Pipewrench View Post
    You got a bad angle stop somewhere
    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.

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