# knocking sound only when water is off



## awalts (Oct 17, 2011)

As shown in the videos, the noise is a rapid, loud, rhythmic beating  that can change in tempo, duration (usually 30 seconds or less), and  volume. The noise always comes from the same location in the house - it  seems to be in the interstitial space between the basement and first  floor, roughly near/above (but not in) the water heater, and this  happens to be near the spigot at the back of the house.

Before the noise starts, no water is running. None of our toilets are  leaking, no faucets are dripping, no sinks are running etc ... In  addition it does not correlate with the automatic ice maker so far as I  can tell.

Having said that, once the noise does start, if any water valve is  opened (faucet, back spigot, toilet etc) the noise stops instantly. Some  times it comes back in a few minutes, some times it doesn't start again  for hours. Usually we hear it at least once a day, but that depends on  how much we are home.

Things I have tried include flushing the water heater (although I don't  think it is minerals in the water heater) and draining all of the water  from the house in case this was a water hammer issue (both plumbers  didn't think it was this). I've tried each several times, but neither  has helped alleviate the problem.

The most recent thing we have tried came at the suggestion of one  plumber. On his advice we asked the county to give us a new water  meeter. They claim to have done this, but the noise is still there.

Here are two videos of the noise:
[ame]Http://www.youtube.com/watch?v=UODyZz2OeIU&feature=mfu_in_order&list=UL[/ame]

So I'm hoping someone might have an idea or two about what is causing  this noise. I can call another plumber but paying some money to have  someone come out and say "I don't know" doesn't seem productive.

Thank you for the help


----------



## paul52446m (Oct 17, 2011)

awalts said:


> As shown in the videos, the noise is a rapid, loud, rhythmic beating  that can change in tempo, duration (usually 30 seconds or less), and  volume. The noise always comes from the same location in the house - it  seems to be in the interstitial space between the basement and first  floor, roughly near/above (but not in) the water heater, and this  happens to be near the spigot at the back of the house.
> 
> Before the noise starts, no water is running. None of our toilets are  leaking, no faucets are dripping, no sinks are running etc ... In  addition it does not correlate with the automatic ice maker so far as I  can tell.
> 
> ...


Do you have any check valves in you cold water lines. Any check valves between the cold inlet of water heater and the well tank? Does your water heater relief valve ever pop off?  Paul


----------



## Redwood (Oct 18, 2011)

Bet you have a leaking flapper in a toilet...
And a korky fill valve....


----------



## awalts (Oct 18, 2011)

paul52446m, there is a PRV valve where the cold water comes into the house. Can this be the cause of the noise? If so, how do I prove it and can I easily replace the valve?

Redwood, If it were a toilet, I should be able to sequentially turn off the water to all of the the toilets and eventually find if that is the cause correct? I'll give that a try, but I've been listening pretty closely and never heard the water running to refill a toilet. 

Thanks
Avram


----------



## awalts (Oct 18, 2011)

paul52446m, there is a PRV where the cold water enters the house. If this is the source of the knocking, how do I prove it and how do I replace it?

redwood, if it is a leaky toilet, then I should be able to isolate the problem by sequentially turning the water off at different toilets. I've listened pretty closely though and I don't think I have a leaky toilet. The water bill hasn't changed much either ...

Thanks
Avram


----------



## Redwood (Oct 18, 2011)

Have you looked at the water meter while the knocking is occurring?
I guarantee that it is spinning...


----------



## nealtw (Oct 18, 2011)

I don't have an answer so I will ask a question. How much expansion can you get from copper pipe when it heats up and if it were in a tight hole could you get noise when it heats or cools.


----------



## paul52446m (Oct 18, 2011)

nealtw said:


> I don't have an answer so I will ask a question. How much expansion can you get from copper pipe when it heats up and if it were in a tight hole could you get noise when it heats or cools.



Your idea is the two things i was looking at. One if the water heater comes on so the hot water has to expand some where. I had one where they put in a softener system and they had a check valve on the cold line so the water heater could not expand back into a expansion tank. so it would pop off and bang the pipes.  I put a expansion tank on the hot side of the water heater.
 You are right on a hot water copper line going through a tight wood hole. When it heats up it can make a real loud noise as it moves in the hole.  Paul


----------



## Shawner (Oct 18, 2011)

Have you tried shutting off the water completely to absolutely confirm it's the water lines?

We had an almost identical problem here at a home in my town.  The noise was usually at about the same time in the morning, right after they woke up.  Happened before use, seemed to quiet after water was turned on.  We changed out the meter with no luck, then removed the meter completely.  Still not a fix.

Suggested to the fellow to try changing out his PRV and left it at that.  

Spoke to him about 2 weeks later and asked him how he made out.  Turns out it was a woodpecker banging on the back of the house


----------



## awalts (Oct 19, 2011)

I wish it were as a simple as a woodpecker. But the knocking is as likely to occur at 10pm as 10am. 

I have had the water off to the house for periods of 8 hours and not heard the knocking. When I do hear the knocking, the water to the house is on, nothing is running or leaking so far as I know, and it is independent of the on/off status of the AC and heat (I thought it might be something lose in the HVAC system).


----------



## Redwood (Oct 19, 2011)

awalts said:


> I have had the water off to the house for periods of 8 hours and not heard the knocking. When I do hear the knocking, the water to the house is on, nothing is running or leaking so far as I know



That says leak!

Dye Test your toilets!


----------



## isola96 (Oct 19, 2011)

This could be the fluid master in the tank 
If you don't see water running around the inside bowl your flapper is ok


----------



## Redwood (Oct 19, 2011)

isola96 said:


> This could be the fluid master in the tank
> If you don't see water running around the inside bowl your flapper is ok



Actually the Korky fill valves are far more likely to pulse the flow like that than a Fluidmaster when the flapper is leaking....


----------



## isola96 (Oct 19, 2011)

Redwood said:
			
		

> Actually the Korky fill valves are far more likely to pulse the flow like that than a Fluidmaster when the flapper is leaking....



No sorry 2 different ideas one chance fluid master two if the water isn't trickling inside the bowl then flapper is fine


----------



## nealtw (Oct 19, 2011)

If it isn't plumbing then let's talk about duct work and metal chimneys!


----------



## isola96 (Oct 19, 2011)

nealtw said:
			
		

> If it isn't plumbing then let's talk about duct work and metal chimneys!



No it's plumbing aright unless your being sarcastic lol

Did you turn the shut off to the toilet off and listen for the noise?


----------



## Speedbump (Oct 20, 2011)

I saw this earlier this morning on All Experts and from the Video, I thought I was looking at a Hydronic heating system.  They are famous for making noises.  Not like the one in the video exactly, but that is what it looked like to me.

Redwood, isn't that what I'm seeing.  Valves with tags on them probably describing what part of the house they service etc.


----------



## Redwood (Oct 20, 2011)

Could be...

I didn't initially watch much of the 2 videos...
Only one appeared in the thread and I got dizzy with the spinning camera.... 

looking at it again I found the playlist link and got dizzy again but yea it looks like a heating system...

What have you got there...


----------



## Speedbump (Oct 20, 2011)

I watched it then got up too quick... almost fell over.


----------



## awalts (Oct 20, 2011)

Nope, I have a normal gas heating system, not a hydronic one. The pipes are just cold water lines coming off the main and heading to the outside spigots. The tags were put on by the house inspector just marking what each valve does (front, back, water heater etc). I'll turn off the toilet (s) this weekend - I wanted to do it when I was home for a decent amount of time.


----------



## isola96 (Oct 20, 2011)

awalts said:
			
		

> Nope, I have a normal gas heating system, not a hydronic one. The pipes are just cold water lines coming off the main and heading to the outside spigots. The tags were put on by the house inspector just marking what each valve does (front, back, water heater etc). I'll turn off the toilet (s) this weekend - I wanted to do it when I was home for a decent amount of time.



We're does the shut off that is on the off position go?.. And why is it off?....

You have or don't have your heat on 
Is it controlled at the radiator or thermostats.


----------



## awalts (Oct 23, 2011)

I turned off the water to each toilet (and then all of them at the same time), and the knocking still persists.

The two valves (one shut off, one not) go to the outside spigots (front and back). The knocking sound occurs regardless of their on/off setting. 

Lastly, another video of the knocking. Sorry for the initial camera movement. The knocking comes on very suddenly at the 19 second mark, grows in intensity and volume, and then stops after about 4 seconds. It starts and stops in spurts like this, sometimes once or twice, sometimes many times over a 30 minute period.
[ame=http://www.youtube.com/watch?v=U3TY_Md2zes&feature=related]00002.MTS - YouTube[/ame] 

If it is the pressure reducing valve, any thoughts on how much that costs to replace?


----------



## awalts (Nov 6, 2011)

I have an update to add to this knocking issue ...

I bought a pressure meter and attached it one of the outdoor spigots. Normally the water pressure is about 70 psi and the needle does not move. However, when the knocking sound occurs, the needle shakes/fluctuates between 60 and 70 psi. So long as the noise is being made, the needle shakes. As soon as the knocking stops, the needles returns to holding steady at 70psi.

Any thought now on what needs to be fixed?
Thanks again
Avram


----------



## joecaption (Nov 6, 2011)

Any chance there's a recirulating pump on the hot water line? It cirulates the water so as soon as a taps turned on the waters hot.


----------



## paul52446m (Nov 6, 2011)

awalts said:


> I have an update to add to this knocking issue ...
> 
> I bought a pressure meter and attached it one of the outdoor spigots. Normally the water pressure is about 70 psi and the needle does not move. However, when the knocking sound occurs, the needle shakes/fluctuates between 60 and 70 psi. So long as the noise is being made, the needle shakes. As soon as the knocking stops, the needles returns to holding steady at 70psi.
> 
> ...


I am not a plumber, but  I have had two different Gas regulator, one LP and one Nat gas, that were a little to much clearance in side so when they would operate at times they would not only go up and down, they would violently vibrate and raddled all the gas piping in the house. Have you had them change the regulator yet. When that happened to me the first time i could not believe the noise it made. I had just put the new boiler system in so the regulator was new but defective.   Paul


----------



## isola96 (Nov 6, 2011)

So when exactly does the sound accrue? 
Did we eliminate heat? Because it happens when the heat is off?
Is anything running dishwasher shower ect? How do we know that it's hot water line we don't so how about fluid master goes bad happend to me a few times it made the hole line shake like crazy I thought it was a ball valve not opened all the way but no it was fluid master.
Turning on the out side spickit could cause this as if you have alot of pressor in your lines check your boiler and or hot water heater check for feeder valves to either boiler or tank to give it water.
If any circulators u have feel them make shore they are not over heating.


----------



## joecaption (Nov 7, 2011)

70 PSI is a whole lot more then I've ever seen a fresh water system set it. The highest I've seen is 50 PSI, and I've worked on and built hundreds of homes in my life time.


----------



## Speedbump (Nov 7, 2011)

> 70 PSI is a whole lot more then I've ever seen a fresh water system set it. The highest I've seen is 50 PSI, and I've worked on and built hundreds of homes in my life time.


The only time I had city (county) water in my entire life was ten years ago and that static pressure was 85 psi.


----------



## evstarr (Nov 16, 2011)

Have you been lucky enough to be able to time it so you can actually touch the various pipes while the knocking is going on to see if it's a particular line?


----------



## parmila2000 (Nov 18, 2012)

Any luck in finding what the real problem was?...we are facing the same issue in our house....please help


----------



## awalts (Nov 19, 2012)

It turned out to be the Water Pressure Reducing Valve. I  lowered the household water pressure (loosened the valve) and then slowly brought it back to the original pressure. And the knocking went away. I can't explain why it worked, but it did. We haven't heard the knocking sound in over a year.


----------



## Wuzzat? (Nov 19, 2012)

awalts said:


> It turned out to be the Water Pressure Reducing Valve. I  lowered the household water pressure (loosened the valve) and then slowly brought it back to the original pressure. And the knocking went away. I can't explain why it worked, but it did. We haven't heard the knocking sound in over a year.


Something may reinitiate it, but at least you know a fix that works for now.


----------



## jj_iitk (Nov 24, 2012)

hi, we have exactly the same problem as yours. Where did you find your water pressure reducing valve? does every house has it?


----------



## Shawner (Nov 24, 2012)

jj_iitk said:


> hi, we have exactly the same problem as yours. Where did you find your water pressure reducing valve? does every house has it?



Not every house has one but every house should (if connected to a municipal source).  They're typically located right after the main shutoff valve where the water enters your house.


----------



## Wuzzat? (Nov 25, 2012)

jj_iitk said:


> does every house has it?


You want more than 20 PSI static pressure into your house for sanitary reasons and less than 80 PSI to make the pipes last long.
Max flow rate may be 16 GPM but there may be a minimum for sanitary reasons.


----------

