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Thread: Bang/pop noise in drains after dark

  1. #1
    DIY Junior Member plumbingnewguy's Avatar
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    Default Bang/pop noise in drains after dark

    Every night after my wife takes a shower, what I believe to be our PVC drain will make a quick banging-type noise every half hour to an hour over the course of a couple hours. I will hear it very occasionally in the morning too. It's just a quick bang that lasts less than a second. This only is in our master bathroom shower as well. The other bathroom has never had this issue. It doesn't keep us up at night - It's just more an annoyance.

    I don't think it's the supply lines - Every visible supply line in the house I've ever seen appears to have Water Hammer Arresters installed at the source, from the dishwasher to the washing machine.

    It's a 3 floor townhouse that's less than 20 years old, however, there were some corners cut here at building time that the original owners didn't believe needed addressing I guess so it wouldn't surprise me that the builders didn't just fasten the pipes and call it a day. It tends to happen more when the weather gets cold. It's hardly an issue in the summer (you might hear it once a night a half hour or so after she showers) but tends to creep up more between September and April or so.

    Is this nothing more than the expanding/contracting of the pipe due to the weather?

    Cheers

  2. #2
    Plumbing Contractor for 49 years johnjh2o1's Avatar
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    What you may be hearing is the expansion and contraction of the water lines as they heat up and cool down.

    John

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    Forum Admin, Expert Plumber Terry's Avatar
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    Like John says.
    Pipes expand and lengthen while running warm water through them, as they cool, they contract.
    That can cause an assortment of knocking, ticking and clunking sounds in the wall.
    Sometimes caused by pipes being strapped down, or in snug holes that grip the pipe too tightly. Lay a pipe in the sun, and the side toward the sun gets longer and bends the pipe.

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    DIY Junior Member plumbingnewguy's Avatar
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    Hi guys,

    Thank you for the insight. Glad it's just part of the rigors of ownership then.

    If it's the water lines themselves, does this actually do anything negatively to them over time, or can I sleep safely at night knowing it's just same old same old? We're built on the tail end of the Polybutylene era, and we manage well all things considered - All copper fittings, hot water tank is set to the lowest heat setting, water pressure is below the pipe's "manageable" levels but enough to get a good shower, etc etc.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    There's a nice graph of the expansion rates of various plumbing pipe here http://www.engineeringtoolbox.com/th...pvc-d_782.html .

    Often, it's just annoying. It depends on what it is rubbing on...the moving back and forth could wear a hole in it - if it's just a slightly tight hole, probably not. In really long runs, there could be enough movement that it could crack itself or a fitting if that movement wasn't accommodated. The temperature differences often seen in a home help to limit the expansion and corresponding contraction. It's pretty dramatic when I empty the boiling water from say a pot of pasta down the drain, though, in my home!
    Jim DeBruycker
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    Moderator & Master Plumber hj's Avatar
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    A "bang" such as you describe is often caused by a elbow almost touching a wall, and then hitting the wall when the pipe expands due to hot water flow. Years ago a factory heard a loud "bang" every morning when they turned the steam on. They never checked WHY it was happening, and just accepted that it was part fo the system, at least until one morning when a 6" cast iron elbow finally gave up the ghost and cracked.
    Licensed residential and commercial plumber

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    DIY Junior Member linda99's Avatar
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    Default water drip noise when hot water faucet is on but no wet spot around

    I noticed some water dripping noise when flushing hot water from the second floor sink. There is no such noise when flushing cold water only. I didn't observe such noise before. But I haven't found any wet spot on the ceiling or the wall on the first floor where the water pipes go down. The wall is inside the house and it has two sides. one side is installed with microwave, oven and cabinets. the other wall is installed with cabinets. So most wall area is blocked with cabinets and appliances. I cannot see wet spots in the open area or inside the cabinets.


    Is there water leakage? This is a 2-year old house and I will be very disappointed with the quality if it has leakage.
    What should I do next?

    Thanks for suggestions!!!
    Last edited by linda99; 10-30-2013 at 06:14 PM.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Is it more of a tick-tick sound? Hard to say without being there. Most newer houses use PVC or ABS drain pipes. These expand/contract much more than cast iron pipes (still used in premium houses and in some situations by code for fire reasons). When using hot water, that expands the pipe, then, after you stop, it will then cool off and contract back. Depending on how it is routed and anchored, it can easily make some sounds as it changes size, then 'snaps' against the tight spot, maybe doing that multiple times. The fact it doesn't do it with cold, leads to that expansion/contraction...common, but if the run is designed and installed well, need not happen.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member linda99's Avatar
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    Hi jadnashua, it's like tick-tick noise.

    Your explanation makes sense to me. Although you didn't make a conclusion, sounds like you think this is a normal problem and is not leakage?
    The description above is what I observed so far. Is there any else I can do for further diagnosis?

    Or should I request some plumbing service soon? Right now, we stopped using that sink, just don't want to make it worse if there is indeed leaking.

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    DIY Junior Member linda99's Avatar
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    Just want to add some information about the wall where the drain pipes go down.

    The wall is inside the house and it has two sides. one side is installed with microwave, oven and cabinets. the other wall is installed with cabinets. So most wall area is blocked with cabinets and appliances. I cannot see wet spots in the open area or inside the cabinets.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    It is probably is not a leak, otherwise, it would do it when you ran cold water as well. It's a sign of sloppy workmanship. Usually it isn't more than an annoyance. To fix it, you'd need to open up the wall and find out where it is sticking, then either reroute or open up or loosen the clamp or hole the pipe is going through.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Forum Admin, Expert Plumber Terry's Avatar
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    Pipes expand and lengthen while running warm water through them, as they cool, they contract.
    That can cause an assortment of knocking, ticking and clunking sounds in the wall.
    Sometimes caused by pipes being strapped down, or in snug holes that grip the pipe too tightly. Lay a pipe in the sun, and the side toward the sun gets longer and bends the pipe.

    I used to pride myself in cutting nice small holes for my plumbing layouts. After a few service calls to determine noises in the wall from showers, I started drilling a larger hole for the shower line. I also gave it more distance before wying into the main stack.
    I figured if there was nothing for the pipe to touch up against, there was less chance of binding when it got warm. The noise mostly happens during the cooling phase.
    Last edited by Terry; 10-31-2013 at 11:20 AM.

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    DIY Junior Member plumbingnewguy's Avatar
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    Quote Originally Posted by jadnashua View Post
    There's a nice graph of the expansion rates of various plumbing pipe here http://www.engineeringtoolbox.com/th...pvc-d_782.html .

    Often, it's just annoying. It depends on what it is rubbing on...the moving back and forth could wear a hole in it - if it's just a slightly tight hole, probably not. In really long runs, there could be enough movement that it could crack itself or a fitting if that movement wasn't accommodated. The temperature differences often seen in a home help to limit the expansion and corresponding contraction. It's pretty dramatic when I empty the boiling water from say a pot of pasta down the drain, though, in my home!
    Haha! Yeah I'm surprised we don't hear more of that noise when we are dumping a pot of pasta water down the sink. It doesn't really happen in any of the other rooms of the house -- Just the master bath.

    So I did manage to pinpoint the noise based on the way I believe our supply lines run. It's 100% the PVC drain in the shower - The Poly B supply lines run under the master bedroom floor, and I'll hear them expanding/contracting once if that. The master bath has its own drainage pipe separate from the rest of the house that runs between the living room and exterior wall to a pipe in the crawlspace/storage, and is probably runs within a few feet of one of the furnace outside air vents...so I guess there's your culprit since it happens after showers and sometimes a couple times a night when it starts to get coldest outside.

    As long as I know it's not a problem, I'll chalk it up to being an annoyance more than anything. Funny thing is this has probably been going on ever since we moved in nearly 7 years ago and even before with the old owners...I've just never paid attention to my surroundings well enough I suppose.

    Thanks for your insight everybody. This has put my mind at ease.

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    DIY Junior Member linda99's Avatar
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    Quote Originally Posted by Terry View Post
    Pipes expand and lengthen while running warm water through them, as they cool, they contract.
    That can cause an assortment of knocking, ticking and clunking sounds in the wall.
    Sometimes caused by pipes being strapped down, or in snug holes that grip the pipe too tightly. Lay a pipe in the sun, and the side toward the sun gets longer and bends the pipe.

    I used to pride myself in cutting nice small holes for my plumbing layouts. After a few service calls to determine noises in the wall from showers, I started drilling a larger hole for the shower line. I also gave it more distance before wying into the main stack.
    I figured if there was nothing for the pipe to touch up against, there was less chance of binding when it got warm. The noise mostly happens during the cooling phase.
    Hi Terry, I am not a handy man and not able to do what you suggested "Lay a pipe in the sun, and the side toward the sun gets longer and bends the pipe".
    Is there a potential concern or leakage risk if I don't do anything now? One option I was thinking is to stop using the sink and wait till spring to see whether it happens again and decide whether it needs some fix. Is it a good idea?

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    Forum Admin, Expert Plumber Terry's Avatar
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    What is happening is very normal.
    Plastic expands and rubs against wood. This sort of thing has been going on for decades without an issue.
    A Furnace will have simalar issues. The pipes warm up, and then they cool. As they cool things slip back into postion again.
    A home that faces the South in the Summer, will get taller on the sunny side. In the evening, after the sun goes down, the house contracts on that side, causing all sorts of sounds as the different pieces rearrange themselves.
    I notice that in the Winter, after the leaves have fallen, I hear the freeway better at night. I don't notice so much in the Summer with more leaves between me and the freeway a half mile away.

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