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Thread: Water Pipe Hammering

  1. #1
    DIY Junior Member wee-haggis's Avatar
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    Default Water Pipe Hammering

    I recently moved into a 50 year old house and started to noticed water hammering (at least I think that what it is).
    No matter which faucet I turn on or off it...clunks each time (bathroom ,shower,washer,kitchen etc).
    It appears to be coming from a semi-inaccessible location in the basement ,above the gas water tank.
    Although I have'nt measured the water pressure coming in, it appears to be quite high (but not overly so).
    If I have the cold water running then turn the hot water tap of and on....there is no clunking, if I turn the hot water off and on ,on its own...it clunks.
    The hammering is coming from the general area above the water tank which I can partially view. As far as I can see the pipes pass through tight holes in joists but are other wise un-clipped.
    Is this something a water hammer arrestor could solve, if so where would be the best place to locate it and would it be needed on both hot and cold ?

    Thanks

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    DIY Senior Member kcodyjr's Avatar
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    Hammering *everywhere* is a little bit suspect, IMO. It's only commonplace where fast-closing solenoid valves are involved, or when you turn a valve quickly from max to zero.

    I think your first move should be to measure your static water pressure. You might need a pressure reducing valve (PRV, or regulator).

    If that's not it, then you'll need hammer arrestors. To work properly, they need to be installed right next to each fixture. To explain that: water hammer happens because water has momentum, like everything else in the universe. When a valve closes, there's nowhere for that moving water to go except to slam into the valve. This creates a pressure wave that travels backward through the pipe at the speed of sound, stressing every part of the system. This energy usually spent making the pipes jump around and whack into the wall, hence the noise, but sometimes the result is a blown joint. A hammer arrestor is basically a shock absorber that prevents the pressure wave from forming.

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    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by wee-haggis View Post
    I recently moved into a 50 year old house and started to noticed water hammering (at least I think that what it is).
    My take is that what you are hearing is heat traps on the HWT, not water hammer.

  4. #4
    DIY Junior Member wee-haggis's Avatar
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    Quote Originally Posted by kcodyjr View Post
    Hammering *everywhere* is a little bit suspect, IMO. It's only commonplace where fast-closing solenoid valves are involved, or when you turn a valve quickly from max to zero.

    I think your first move should be to measure your static water pressure. You might need a pressure reducing valve (PRV, or regulator).

    If that's not it, then you'll need hammer arrestors. To work properly, they need to be installed right next to each fixture. To explain that: water hammer happens because water has momentum, like everything else in the universe. When a valve closes, there's nowhere for that moving water to go except to slam into the valve. This creates a pressure wave that travels backward through the pipe at the speed of sound, stressing every part of the system. This energy usually spent making the pipes jump around and whack into the wall, hence the noise, but sometimes the result is a blown joint. A hammer arrestor is basically a shock absorber that prevents the pressure wave from forming.
    Thanks.
    Appreciate explanation

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    DIY Junior Member wee-haggis's Avatar
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    Quote Originally Posted by LLigetfa View Post
    My take is that what you are hearing is heat traps on the HWT, not water hammer.
    If indeeds its heat traps,how is this resolved ?
    Thanks

  6. #6
    Forum Admin, Expert Plumber Terry's Avatar
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    Quote Originally Posted by wee-haggis View Post
    If indeeds its heat traps,how is this resolved ?
    Thanks
    Remove the pipe nipples with heat traps.
    I just did that this morning for a customer. No hammer on that one, but flow was restricting, and noise volumne had gone up.
    Pulled the nipples with ball checks and that solved it.

  7. #7
    DIY Junior Member wee-haggis's Avatar
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    Amateur here,so assistance needed.
    I've attached a photo showing my tank. Cold water on right (3/4" or 5/8") and hot on the left (1/2").
    Name:  IMG_0111.jpg
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Size:  44.5 KB

  8. #8
    Test, Don't Guess! cacher_chick's Avatar
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    I would be looking for a section of pipe that is not properly supported and is banging on a framing member or another pipe.

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    DIY Senior Member kcodyjr's Avatar
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    cacher_chick's suggestion is as excellent as her tagline, but bear in mind it makes the assumption that the problem is indeed hammering resulting in pipe movement resulting in an audible banging noise.

    There might still be something to the other theory of a bad heat trap, and independently of that, a static pressure test is still a good idea.

    It isn't clear, does the effect occur when messing with the cold water alone? How about when the toilet shuts off?

  10. #10
    Moderator & Master Plumber hj's Avatar
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    I disconnect the pipes from the water heaters and extract the plastic, or metal ball, flow check devices.
    Licensed residential and commercial plumber

  11. #11
    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by wee-haggis View Post
    I've attached a photo showing my tank.
    Looks like the same brand/model as my rental tank. It doesn't look like your cold side has a union, so it would require cutting and sweating.

    I just put up with the clunking noise. Every now and then the traps stick from sediment and affect the flow. At one point I queued up a service call with the rental agency to remove the traps but it cleared itself up so the wife cancelled the service call.

  12. #12
    DIY Junior Member wee-haggis's Avatar
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    I took some photos in inaccessible areas and what you see is the hot water pipe (in the foreground) going from right to left (then down to bathroom sink),the pipe beyond that is the cold water line teeing off of the main incoming water supply (which then carries on to the water tank). It appears that the hot pipe is sitting on top of the cold (even looks like its making some sort of rubbing mark). Could this be tjhe problem ?
    Thanks
    Name:  1.jpg
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  13. #13
    DIYer, not in the trades LLigetfa's Avatar
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    Use a stethoscope to narrow down where the sound is coming from.

  14. #14
    DIY Junior Member wee-haggis's Avatar
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    Quote Originally Posted by LLigetfa View Post
    Use a stethoscope to narrow down where the sound is coming from.
    I have already determinded that the sound is coming from the area shown in the previous image

  15. #15
    DIY Senior Member kcodyjr's Avatar
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    Quote Originally Posted by wee-haggis View Post
    sound is coming from the area shown in the previous image
    Insufficient resolution for a conclusion. If you want to be sure of what you're going after, you need to pinpoint the sound.

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