Is this what knocking pipes sound like?

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There is a muffled boom type of noise in my home, sometimes loud, sometimes soft. It is not always in the same place. It usually sounds like it is c oming from the crawl space, but also behind the walls.
Can it be knocking pipes, the stuff that happens when there is a problem wi th air pressure in the pipes? What makes me question this is: (1) It does n't really sound like water moving in a pipe, and (2) it happens all day an d night, not just when I run water. Does that sound like I need to call a plumber? (BTW, I've read about fixing knocking pipes but what I think is t he main valve is something that I can't easily turn off, so I'm not sure. I'd feel better with a plumber).
Before anyone suggests it might be water radiators, I have forced hot air, and it is turned off now anyway.
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On 10/8/2013 9:51 AM, Dom wrote:

the same place. It usually sounds like it is coming from the crawl space, but also behind the walls.

makes me question this is: (1) It doesn't really sound like water moving in a pipe, and (2) it happens all day and night, not just when I run water. Does that sound like I need to call a plumber? (BTW, I've read about fixing knocking pipes but what I think is the main valve is something that I can't easily turn off, so I'm not sure. I'd feel better with a plumber).

One possible answer, is the heating ducts. if there's a bit of wind, the changing air pressure might be flexing the ducts. We don't have a lot of information to go with.
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wrote:

plumbing problem to me. It sounds like something expanding and/or contracting as it heats or cools. It could be wood framing, HVAC ducts, or plumbing. Knocking pipes (water hammer) normally occurs as water is turned on or off. It is caused by having a stream of water in a pipe try to keep moving (via momentum) when you turn the water off suddenly. The pipe moves back when the water is turned on suddenly. It can have enough force to make the pipe touch another pipe or a wood stud. That is unlikely to be your problem if you aren't using water when you hear the noise. Does the noise happen when the sun is heating the house or when a clear sky causes rapid cooling at night? If so, it is just a nusance.
Pat
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On Tuesday, October 8, 2013 10:25:58 AM UTC-4, Pat wrote:

s coming from the crawl space, but also behind the walls.

oesn't really sound like water moving in a pipe, and (2) it happens all day and night, not just when I run water. Does that sound like I need to call a plumber? (BTW, I've read about fixing knocking pipes but what I think i s the main valve is something that I can't easily turn off, so I'm not sure . I'd feel better with a plumber).

Thanks for the info. I do have trouble with one duct making loud clangs wh en the heat goes on and off, and I already have an estimate to have the duc t removed (from the ceiling!) and replaced with a plastic one. My wood flo ors make a pop every now and then. (It's like I live in a ghost house!) Bu t this is more of a muffled noise, and it does not seem to be coming from t he duct or the floor.
I'd like to turn off the main valve and flush all the water from the faucet s and toilets, and then turn it back on. That seems cheap and easy, but I just don't know what I'm doing.
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"Dom" wrote in message
On Tuesday, October 8, 2013 10:25:58 AM UTC-4, Pat wrote:

Thanks for the info. I do have trouble with one duct making loud clangs when the heat goes on and off, and I already have an estimate to have the duct removed (from the ceiling!) and replaced with a plastic one. My wood floors make a pop every now and then. (It's like I live in a ghost house!) But this is more of a muffled noise, and it does not seem to be coming from the duct or the floor.
I'd like to turn off the main valve and flush all the water from the faucets and toilets, and then turn it back on. That seems cheap and easy, but I just don't know what I'm doing.
Dom.. I have always added a second main line water turn off in series with the main one. Put it in a cabinet in a bath room. This way can shut off easy to do faucet repairs if needed. WW
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I'd have to agree. Flushing your water pipes to cure a noise? A noise made while you aren't using water? You really don't know what you're doing.
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Dan Espen

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On Tuesday, October 8, 2013 10:48:27 AM UTC-4, net cop wrote:

Well, Dan, that's why I asked if this problem sounds like knocking pipes or not. Your answer is no, it is not, and I'll buy that. Any idea what it is, or how I should go about finding out what is causing it?
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Without hearing the sound, it's hard to guess. I think I'd try to isolate by finding where it's loudest. Have other household members help.
I'd lean toward expansion/contraction. Note times of day, frequency, any weather conditions.
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Dan Espen

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Yes, that is a well known (possible) cure for water hammer. Perhaps "flush" is not the correct word, and I'm not saying that the noise that Dom is hearing is water hammer, but "Flushing your water pipes to cure a noise" is known to work in many cases.
Stolen without permission from http://en.wikipedia.org/wiki/Water_hammer
"Where air filled traps are used, these eventually become depleted of their trapped air over a long period of time through absorption into the water. This can be cured by shutting off the supply, opening taps at the highest and lowest locations to drain the system (thereby restoring air to the traps), and then closing the taps and re-opening the supply."

Water pipe noises can occur even when the homeowner is not - or does not know that he is - using water. A slowly leaking toilet could be filling without his knowledge and the valve could be shutting quickly. One way to check is to read the meter before going out for an extended period and then read it again when you get back. Any water usage would indicate a leak someplace in the system. Could even be a humidifier filing up.
Since draining the system is free and typically easy, it certainly can't hurt to try it. Yes, Dom needs to figure out how to close the main shutoff, but once he does that, it can't hurt to try a drain and fill.

Be nice.
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On Tuesday, October 8, 2013 12:55:07 PM UTC-4, DerbyDad03 wrote:

ck on. That seems cheap and >> easy, but I just don't know what I'm doing.

he correct word, and I'm not saying that the noise that Dom is hearing is w ater hammer, but "Flushing your water pipes to cure a noise" is known to wo rk in many cases. Stolen without permission from http://en.wikipedia.org/wi ki/Water_hammer "Where air filled traps are used, these eventually become d epleted of their trapped air over a long period of time through absorption into the water. This can be cured by shutting off the supply, opening taps at the highest and lowest locations to drain the system (thereby restoring air to the traps), and then closing the taps and re-opening the supply." > A noise made while you aren't using water? Water pipe noises can occur even when the homeowner is not - or does not know that he is - using water. A s lowly leaking toilet could be filling without his knowledge and the valve c ould be shutting quickly. One way to check is to read the meter before goin g out for an extended period and then read it again when you get back. Any water usage would indicate a leak someplace in the system. Could even be a humidifier filing up. Since draining the system is free and typically easy, it certainly can't hurt to try it. Yes, Dom needs to figure out how to clo se the main shutoff, but once he does that, it can't hurt to try a drain an d fill. > You really don't know what you're doing. Be nice.
Thank you very much for that DerbyDad. You got my big question: "Can it h appen when there is no water running". And what a great idea: "...read th e meter before going out for an extended period and then read it again when you get back." I was thinking I might have a leaky head in my lawn sprink ler, but I didn't know how to check for that. Now I do!
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A spinning flow indicator only indicates a leak if there is continuously running water. It won't be spinning all the time if a toilet is leaking into the bowl. It will only spin when the float gets low enough for the valve to open.
Unless the OP wants to hang out by the meter all day, reading the meter over a few hours time might help determine if the water is intermittently running.
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Okay, sorry about that. I didn't get the impression from the OP that this was a loud bang which is what I associate with water hammer, plus I'd expect the water to be running at full force.
The OP just said this occurs about once an hour. I'd still try to isolate the sound by hearing. Someone in the house should be close enough to know whether the sound is louder or not so loud in a given room. What he should be looking for is where in the house, then which wall. Then are there pipes in that wall or something else.
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Dan Espen

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On 10/8/2013 12:47 PM, Dan Espen wrote: ...

That may or may not succeed -- noises can be terribly difficult to tell where they originate from inside wall cavities/under crawl spaces, etc., etc., because of traveling along the piping and so on.
_MAY_ be able to tell; may not altho should at least be able to localize a general area and mayhaps from that can then narrow down by tracing plumbing.
The hourly kind of thing does make one think of things like leaks...
To OP...to check a toilet for slow leak, put a tiny drop of food coloring dye in the tank and see if it shows up in the bowl w/o flushing.
Check the float levels aren't up/over the overflow tubes.
The possibility of leaky sprinkler head should be relatively easy to find w/ a waterlogged area...
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Water hammer doesn't have to be a loud bang. I've had 2 instances where the water hammer was a very low, muffled thump-thump-thump.
One was when the local water authority had a problem with the pressure in our water mains and ended up replacing them after the whole neighborhood complained for months about the thumping.
The other time was when my PRV went bad and my whole house was at street pressure. If I shut off any valve, fast or slow, I'd get 3-5 seconds of a muffled, rapid thump-thump-thump-thump.
Maybe the OP should ask the neighbors if they are hearing anything. Once an hour could be a leaky toilet in his house or something with the pumping system in his water authority's infrastructure. I know that's a stretch, but that's how we found out about our town's problems. We got to chatting with the neighbors and they said "Oh, you hear that too? I thought it was something in our house!"
...snip...
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On Tuesday, October 8, 2013 3:05:38 PM UTC-4, DerbyDad03 wrote:

om the >>>> faucets and toilets, and then turn it back on. That seems cheap and >>>> easy, but I just don't know what I'm doing. >>> >>> I'd have to a gree. Flushing your water pipes to cure a noise? >> >> Yes, that is a well known (possible) cure for water hammer. Perhaps "flush" >> is not the corre ct word, and I'm not saying that the noise that Dom is >> hearing is water hammer, but "Flushing your water pipes to cure a noise" is >> known to work in many cases. >> >> Stolen without permission from http://en.wikipedia.or g/wiki/Water_hammer >> >> "Where air filled traps are used, these eventuall y become depleted of their >> trapped air over a long period of time throug h absorption into the water. >> This can be cured by shutting off the suppl y, opening taps at the highest >> and lowest locations to drain the system (thereby restoring air to the >> traps), and then closing the taps and re-o pening the supply." >> >>> A noise made while you aren't using water? >> >> Water pipe noises can occur even when the homeowner is not - or does not >

then >> read it again when you get back. Any water usage would indicate a l eak >> someplace in the system. Could even be a humidifier filing up. >> >> Since draining the system is free and typically easy, it certainly can't >

You really don't know what you're doing. >> >> Be nice. > > Okay, sorry abo ut that. > I didn't get the impression from the OP that this was a loud ban g which > is what I associate with water hammer, Water hammer doesn't have to be a loud bang. I've had 2 instances where the water hammer was a very l ow, muffled thump-thump-thump. One was when the local water authority had a problem with the pressure in our water mains and ended up replacing them a fter the whole neighborhood complained for months about the thumping. The o ther time was when my PRV went bad and my whole house was at street pressur e. If I shut off any valve, fast or slow, I'd get 3-5 seconds of a muffled, rapid thump-thump-thump-thump. Maybe the OP should ask the neighbors if th ey are hearing anything. Once an hour could be a leaky toilet in his house or something with the pumping system in his water authority's infrastructur e. I know that's a stretch, but that's how we found out about our town's pr oblems. We got to chatting with the neighbors and they said "Oh, you hear t hat too? I thought it was something in our house!" ...snip...
Again, great information. I will talk to my neighbor as well as check the meter. And for the record, my noise is best described as "a very low, muff led thump" (not three in a row, but just one). And it happens maybe once a n hour. I had some doubt that it might be a plumbing problem, because to m e it doesn't sound like water.
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On 10/8/2013 2:23 PM, Dom wrote: ...

And, it still may not be (plumbing/water problem, that is)...
If you turn all HVAC completely off, does it still occur? Perhaps it's a return duct getting sucked in if you've got a partially blocked or closed return restricting air flow when the fan kicks on. Or, how long's it been since checked the filters?
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Dom wrote:

I have a tenant who described the same kind of sound, and he is fairly knowledgeable about this kind of stuff (he does handyman/construction-type work). He thought it was possibly coming from the basement or in a wall. In his case, he could usually create the sound by flushing the toilet and then waiting until after it fully re-filled and then he would hear the noise. It also happened at other times without him flushing the toilet. I suggested maybe the toilet flapper and flush valve. I bought them and I was going to do the replacement but he said he would just switch them out on his own (he's a great tenant). That fixed it.
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DerbyDad03 wrote:

I was going to mention the same thing as one possible cause of the "knocking" sound.
The flapper in the toilet could be leaking slowly and/or the flush valve could be causing the knock. The OP could try replacing the flapper in the toilet as a first step, or replace the flapper and the flush valve. Or, shut off the main valve and see if the noise goes away with the main valve shut off. Of course, that would be a pain because he would have to turn the main valve back on every time he wanted to use water for anything and then turn it back off and wait some more to see if he hears any knock with the main valve off.
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wrote:

Draining all the water and then turning it back on as you suggest will add a lot of air to the system. If water hammer is your problem, that air could help because the air sort of acts like a spring to let the water stop more slowly. However, you will also have air spurting out of various faucets until most of that air is gone. The air can loosen up debris that has built up on the inside of your pipes over the years and cause it to clog faucet screens and toilet valves. In other words, you may not fix the problem you are trying to solve, but you could create other problems.
Good luck whatever you decide to do.
Pat
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Dom wrote:

Someone wants to remove the duct from the ceiling and replace it with a "plastic" one? I never heard of a plastic heating/cooling duct, but maybe there is such a thing?
Did you post about the ceiling duct noise here in the past? I remember someone posting about that, and I think he was from my general area (South Jersey).
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