# strange noise under house when irrigation system shuts off



## eitnum (Aug 14, 2014)

Hi all,

I have an irrigation system that runs in the middle of the night. Starting several nights ago, right after the system comes to the end of its run with a sprinkler in the back yard, I hear a low rumbling/rattling/vibrating/pulsating type noise that I believe is coming from under the house. The first time that I paid attention to it, it lasted for about 5 minutes. Last night the same thing occurred, but several minutes after it had stopped, it started up again. I got it to stop by shutting off the entire water supply. When I turned the water supply on again this morning, that noise did not start up again.

The main supply pipe comes into the one-story house below the bathroom. Just inside the foundation a branch goes off to the front yard irrigation. Somewhere else under the house another branch goes off to the back yard irrigation.

The irrigation run starts with two successive zones in the front yard, and ends with three successive zones in the back yard.

It may be that whatever is causing this new noise that I hear after the irrigation system is done has actually started during the irrigation run--but the normal irrigation run noise is so loud that it would be masked.

Does anybody have any idea what could be going on?

Could this have anything to do with siphoning from the irrigation system (although all the valves are anti-siphon), or the $66 Watts pressure regulator put in 5 years ago just beyond the main shut-off?


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## yuri (Nov 29, 2008)

The timer for the system operates a solenoid valve that turns the water on/off. If that valve is worn or not shutting completely you may be getting a chattering sound from it and a sound like water hammer. Or your pressure regulator has failed and there is too much pressure on the solenoid and it is having a hard time closing. I suspect the main problem to be the solenoid and unless it has a maximum input pressure rating then the pressure regulator is not likely the problem.


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## eitnum (Aug 14, 2014)

Thanks, Yuri.

From the instructions that came with the pressure regulator, I see it has a strainer--which has never been cleaned. Could that be the problem?


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## yuri (Nov 29, 2008)

Anything is possible but I doubt it. Clean it anyway. If it was plugged you would not get a good enough stream from the sprinklers but it is worth checking anyway.

If you can manually toggle/turn on the timer or get a helper to do it then you may be able to simulate what is happening if you do it a dozen or more times. Usually these problems get worse or more often so it may not go away but you may be able to catch it in action.


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## eitnum (Aug 14, 2014)

Yuri--or anyone else:

I've been experimenting, and was able to reproduce the noise. I ran the backyard sprinkler by itself tonight. When the remotely-controlled valve shut off, it was entirely normal--no chattering or noise of any kind. I immediately went into the bathroom, and the noise was going on. (The bathroom is right over where the main comes into the house, and further on under the house is where a branch goes off to the backyard irrigation.) I went outside to where the main enters the house, and out there the noise sounds like rattling just inside the wall. While this was going on I went back to the sprinkler valve twice, and nothing was going on there, even with my ear right on the valve. After maybe 10-15 minutes the noise in the bathroom got more irregular and louder. And when I flushed the toilet it stopped!

I did the same experiment yesterday, and the noise didn't happen. But yesterday I turned off the shut-off valve on the FRONT irrigation before running the BACK-yard sprinkler. The branch off to the front irrigation occurs right after the main enters the house--i.e. right where this noise seems to be going on.

I also ran the four other irrigation zones separately, and the only thing of note was that the valve for one drip zone chattered for a few seconds at shut-off, and the valve for another drip zone chattered for a few minutes--but there was no noise in the bathroom.

Does anyone have any further thoughts on this?


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## eitnum (Aug 14, 2014)

This is an addendum to my post of an hour ago.

Re the brass Watts 25AUB-Z3 pressure regulator which was installed five years ago. It is right next to where the noise seems to be coming from. It was set at 55 psi, and that's the pressure reading I'm now getting. (This is well within the range of the irrigation valves.) It may be beyond my ability to get the plug out to clean the filter, as there's little clearance. But I'm sure a plumber could do it. A couple of years ago some work was done on the branch to the front irrigation--just beyond the pressure regulator--and dirt got in, but that's down-stream.


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## yuri (Nov 29, 2008)

You probably need a water hammer arrestor. Google that and then hit>Images.

I doubt it is the PRV as they never shut just modulate. I still suspect one of the solenoid valves but a arrestor may take care of the sound.


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## eitnum (Aug 14, 2014)

Thanks, Yuri.

How long could water hammer continue once it gets started?

And why do you still suspect the irrigation valve solenoid, since it's making no noise?


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