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Thread: Main line leak causing banging noise in house? How to locate?

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    DIY Junior Member JimLS's Avatar
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    Default Main line leak causing banging noise in house? How to locate?

    I have been trying to track down a bumping noise that repeats several times a second. Usually lasts for a second or two. I have checked the toilets, etc and think it may be from a main line leak. There is no pressure regulator. Main line is PVC 1120 with gasketed joints. I turned off the water at the house inlet and checked the meter. The triangle was not moving, at least not fast enough to see. I came back after an hour and the triangle had moved about 1/6 of a turn (or maybe more but the meter hand had not moved enough to see).

    So I am wondering if I have a small leak somewhere that is vibrating and causing the noise. Would a pressure test of the line to the street help determine the issue? It is a 500 foot run - any way to narrow down where the slow leak might be short of digging down midway and cutting the line to cap and test each section? Maybe some sort of sound detection of the vibration?

    At the time the PVC seemed like the way to go. Now I am thinking perhaps I should have used 200 PSI black poly. Anyone have experience with leaking gasketed joints? The line has been in for about 5 years. The line was hit and repaired with the same type gasketed couplings during some yard work near the house about 3 years ago. About 2 years ago some of the line near the street was rerouted, again with the same type materials and joints. The main line has never been pressure tested. What is an appropriate way to test this (pressure, etc)?

    Is it standard/best to run the large PVC or poly pipe into the basement and reduce it there or to reduce the pipe outside and bring in the smaller pipe? Currently it is reduced to 1" copper just outside the house and the copper comes through the basement wall. How is the pipe sealed around? With just concrete or some sort of larger sleeve? I don't want to have to mess with this again...
    Last edited by JimLS; 06-28-2010 at 08:55 AM.

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    Moderator & Master Plumber hj's Avatar
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    As far as I can see, NOTHING in your posting gives us a clue as to why it can be happening. We would have to be there to hear the noise and analyze WHAT is happening in the system to cause the noise at that particular time.

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    DIY Junior Member JimLS's Avatar
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    Default noise

    I was hoping for some ideas of what it could be or what I could check. What sort of further information are you looking for (short of seeing it for yourself )?

    It is a thump, thump, thump at several times a second for a second or two. I suspected toilet valves, loose washer, etc. but my checking of those things has ruled that out for almost everything in the house. What else can I check? I am thinking of putting on a pressure gauge to see if it happens when the pressure is higher. I know my pressure varies a bit.

    My guess/fear is that I have a belled joint gasket that got rolled during installation or damaged somehow and is leaking a very slight amount and vibrating to cause the pressure pulses. Since there seems to be a very slow leak in the main line this seems like a reasonable guess.

    I hope I am completely wrong on this...

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    Forum Admin, Expert Plumber Terry's Avatar
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    Do you have a PRV in the system? They can sometimes create noise in the line.

    Does the thump thump happen after you have used hot water?

    The 1" copper is wrapped in plastic, and then packed with expanding concrete patch.
    Last edited by Terry; 06-28-2010 at 09:17 AM.

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    DIY Junior Member JimLS's Avatar
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    There is no PRV.

    The noise sometimes happens when shutting off faucets (different faucets) and sometimes happens when everything is off with no changes. It isn't related to hot water usage. The noise is not piping expanding and making noise against framing. It is more like water hammer but repeating.

    The copper was not wrapped in plastic. They just used expanding concrete patch.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Concrete in contact with copper isn't a great idea...it should have some resilient material around it. Get a pressure gauge, hook it up, let it sit for a day to see what the average and peak readings are. This requires a gauge with a max reading tattle-tale hand, but most have this.
    Jim DeBruycker
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    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    Quote Originally Posted by JimLS View Post
    I have been trying to track down a bumping noise that repeats several times a second. Usually lasts for a second or two. I have checked the toilets, etc and think it may be from a main line leak. There is no pressure regulator. Main line is PVC 1120 with gasketed joints. I turned off the water at the house inlet and checked the meter. The triangle was not moving, at least not fast enough to see. I came back after an hour and the triangle had moved about 1/6 of a turn (or maybe more but the meter hand had not moved enough to see).

    So I am wondering if I have a small leak somewhere that is vibrating and causing the noise. Would a pressure test of the line to the street help determine the issue? It is a 500 foot run - any way to narrow down where the slow leak might be short of digging down midway and cutting the line to cap and test each section? Maybe some sort of sound detection of the vibration?

    At the time the PVC seemed like the way to go. Now I am thinking perhaps I should have used 200 PSI black poly. Anyone have experience with leaking gasketed joints? The line has been in for about 5 years. The line was hit and repaired with the same type gasketed couplings during some yard work near the house about 3 years ago. About 2 years ago some of the line near the street was rerouted, again with the same type materials and joints. The main line has never been pressure tested. What is an appropriate way to test this (pressure, etc)?

    Is it standard/best to run the large PVC or poly pipe into the basement and reduce it there or to reduce the pipe outside and bring in the smaller pipe? Currently it is reduced to 1" copper just outside the house and the copper comes through the basement wall. How is the pipe sealed around? With just concrete or some sort of larger sleeve? I don't want to have to mess with this again...
    I REALLY doubt the issue you're hearing is anything to do with you a leak in a pipe 500' long. I say this because I have never heard water hammer cause by a leak....

    Are you 100% positive that all of your toilet fill valves are working just fine and not malfunctioning? Try turning off all the shut off valves to the toilets and see if the noise persists.

    I'd also check the hot water tank. Check to see if it's firing at the time of the noises etc.

    I'm also assuming your water meter is at the city connection to your cold water main? If not and the meter is at your house then it spinng wouldn't indicate a leak in your main.

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    DIY Junior Member JimLS's Avatar
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    Quote Originally Posted by Doherty Plumbing View Post
    I REALLY doubt the issue you're hearing is anything to do with you a leak in a pipe 500' long. I say this because I have never heard water hammer cause by a leak....
    I hope you are right. I checked and did not see any flow on the meter with the house shut off. But the pressure was a bit lower at the time - around 50 PSI. It generally runs about 70 PSI. A few days ago I checked and I detected a very slight flow.

    Quote Originally Posted by Doherty Plumbing View Post
    Are you 100% positive that all of your toilet fill valves are working just fine and not malfunctioning? Try turning off all the shut off valves to the toilets and see if the noise persists.
    Already done. Banging happens with them all off. I have also shut off everything else I could get to - sinks, etc. About the only thing I didn't shut off was the ice maker. If the banging starts and I close the main valve into the house the banging stops.

    Quote Originally Posted by Doherty Plumbing View Post
    I'd also check the hot water tank. Check to see if it's firing at the time of the noises etc.
    .
    No. At least the gas one isn't. Not sure about the electric. I know I don't have a check valve in the meter because I could see flow back and forth on the softener as the pressure changed. Without a check valve I am not sure what the heater would have to do with it.

    Quote Originally Posted by Doherty Plumbing View Post
    I'm also assuming your water meter is at the city connection to your cold water main? If not and the meter is at your house then it spinng wouldn't indicate a leak in your main.
    Yes the meter is at the street and then the 500 ft to the house.

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    Forum Admin, Expert Plumber Terry's Avatar
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    The icemaker comes on at all times during the day and night.
    It's a quck closing valve that requires a water hammer arrestor.


  10. #10
    DIY Junior Member JimLS's Avatar
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    I turned off the water heaters just to be sure. After they had been off for several hours I still got the noise.

    About the ice maker... Now that I think about it I am pretty sure it was turned off when I shut off several fixtures in that area with a common filter and shut off. Still had the noise. And the noise often comes in bursts several minutes apart. There should be no way the ice maker is cycling that fast. I will double check that one though.

    The plumbing was done with vertical stubs of capped copper at the fixtures for air chambers. Perhaps I should just completely drain the lines so these can refill with air? I have read that these aren't that effective as air is absorbed into the water over time. But I have no idea how much time that takes. Days? Months? Years? To make sure they are able to refill with air would require the lines to be empty. I am thinking drain the lines at the lowest point and then use a shop vac to clear any remaining water while opening all the fixture valves to let air in. Any thoughts on this?

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