Water Pipe Hammering

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by wee-haggis, Dec 27, 2013.

  1. wee-haggis

    wee-haggis New Member

    Messages:
    10
    Location:
    Ontario
    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
  2. kcodyjr

    kcodyjr New Member

    Messages:
    103
    Location:
    Chelmsford, MA
    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.
  3. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,895
    Location:
    NW Ontario, Canada
    My take is that what you are hearing is heat traps on the HWT, not water hammer.
  4. wee-haggis

    wee-haggis New Member

    Messages:
    10
    Location:
    Ontario
    Thanks.
    Appreciate explanation
  5. wee-haggis

    wee-haggis New Member

    Messages:
    10
    Location:
    Ontario
    If indeeds its heat traps,how is this resolved ?
    Thanks
  6. Terry

    Terry Administrator Staff Member

    Messages:
    14,889
    Location:
    Bothell, Washington
    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. wee-haggis

    wee-haggis New Member

    Messages:
    10
    Location:
    Ontario
    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").
    IMG_0111.jpg
  8. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,244
    Location:
    Land of Cheese
    I would be looking for a section of pipe that is not properly supported and is banging on a framing member or another pipe.
  9. kcodyjr

    kcodyjr New Member

    Messages:
    103
    Location:
    Chelmsford, MA
    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. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,481
    Location:
    Cave Creek, Arizona
    I disconnect the pipes from the water heaters and extract the plastic, or metal ball, flow check devices.
  11. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,895
    Location:
    NW Ontario, Canada
    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. wee-haggis

    wee-haggis New Member

    Messages:
    10
    Location:
    Ontario
    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
    1.jpg
  13. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,895
    Location:
    NW Ontario, Canada
    Use a stethoscope to narrow down where the sound is coming from.
  14. wee-haggis

    wee-haggis New Member

    Messages:
    10
    Location:
    Ontario
    I have already determinded that the sound is coming from the area shown in the previous image
  15. kcodyjr

    kcodyjr New Member

    Messages:
    103
    Location:
    Chelmsford, MA
    Insufficient resolution for a conclusion. If you want to be sure of what you're going after, you need to pinpoint the sound.
  16. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,888
    Location:
    New England
    FWIW, the holes bored into the joists shown in that picture should not have passed an inspection...it's not okay to notch the joist, or bore a hole that close to the edge. WHen you do that, you effectively make the joist only the depth of the notch or hole, making say a 2x10 equivalent to a 2x8 or so. And, there should be metal protection plates to prevent someone from driving a screw or nail into it (normally, only on the wall, since it should not be that close to an edge on a joist).

    The majority of the strength in a joist is from the outer edges...the middle is more for holding them in place (which is why you can bore a hole in it), sort of like an I-beam. Cutting the edge significantly decreases its strength.
  17. kcodyjr

    kcodyjr New Member

    Messages:
    103
    Location:
    Chelmsford, MA
    If the whacking sound has a "clang" in it as well, then yes, those could be hitting there. Is that near the pipes into the heater?

    If it's within reach, you could try stuffing some foam or cloth in between to see if the sound changes.

    I can't emphasize enough though, if you have a hammering problem, suppressing the sound does not solve the real problem.
  18. wee-haggis

    wee-haggis New Member

    Messages:
    10
    Location:
    Ontario
    I've attached a short video. Its an awkward spot to get at ,but I could stand on a stool and stretch over above the water tank to shoot it. This is the area where the clunking is the most obvious (and loudest) although you can hear it throughout the house.
    I did some experimenting yesterday. Turning off hot and cold taps in different parts of the house had the following results. Clunked on,clunked off and I could feel the percussive vibration through the 3/4" incoming cold line to the water tank (just next to where I videoed)NOT through the hot pipe(even although the clunking is by far the loudest when the hot taps are tuned on and off). Although I cannot see past the area in the video, I would guess that the 3/4" incoming line is not fastened (as is the case with the section seen in the video),so its only means of fixing is where it passes through the joist ,cross points. I would also guess that it is sitting very low (almost on top of the drywall ceiling........why they would'nt clip it to the joist on the right is beyond me). This pipe goes for about another 8ft then takes a right turn and goes for about 20ft to the meter.
    [video=youtube;lgXi6IOSIO8]http://www.youtube.com/watch?v=lgXi6IOSIO8&feature=youtu.be[/video]
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