Water Hammer/gas Hammer?

smellslike$tome

HO has a funny noise in her kitchen that happens 1-3 various times a day. She thinks it may be plumbing related. What she describes sounds like water hammer only of course it never happens when I am there. Problem is that she can not associate it with the operation of any plumbing fixture because it always happens when nothing, to her knowledge is being operated. So the first thing I do is check her water pressure to see if maybe her water heater is bleeding off which is something she wouldn't necessarily know. Pressure is normal. I ask her about the ice maker, "no the im isn't doing anything when it happens". The toilets don't leak and are at the other end of the house anyway. So I still haven't heard it but I explain that what she is describing is water hammer but that it does'nt fit the scenario. Quote her a price to install 2 water hammer arrestors in the crawl space under the kitchen. I explain to her that I am suggesting this based on her testimony but that I can't guarantee that it will work. She oks the work. So now I'm under the house and my confidence is very low 'cause I have no idea if this will help or not. I really am not even sure that it is a plumbing problem at all. She was very specific in her location of "ground zero" which was right in front of the left of 2 single bowl kitchen sinks (sort of funny looking to me kind of like a double lav in your kitchen). So when I get to the spot in the crawl space the first thing I see is a 2# gas regulator in almost exactly (within one foot) the spot she indicated. The regulator serves a gas range in an island which has not been in use at any time that the noise has been heard. Well I'm staring at this thing thinking how odd it's location is with respect to the problem at hand. I'm also thinking thats ridiculous 2# gas could scarcely move a feather much less a regulator with all it's attached piping. But then I started thinking about how a balloon acts when you haven't tied a knot in it and then you let just a little air out, you know, how it squeals and carries on and so I wondered if the vent on the regulator could possibly be relieving excessive gas pressure and making the noise. I have no idea about what I'm saying and have never even seen, to my knowledge, a regulator vent in action.

Does anybody have any idea about this. I'm sure it's not the regulator but I can't explain the source of the noise.

P.S. I told the HO we should wait and see if she can pinpoint the source when it happens again rather than resorting to exploratory surgery which will cost her a bunch of money and may not even solve the problem.

Any ideas will be greatly appreciated.

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KillerToiletSpider

Gas regulators do go bad, I have heard them squeal when venting because they are not working properly, never heard one thump, but I would not rule out the possibility. I would see what a 28" WC to 7" WC regulator costs in your area, around here they are about twenty bucks, and replace it.

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The plumber

The old mysterious noise. I had that happen years ago and I don't believe we ever got it figured out. I was there for hours and no noise. All you can do is guess at this point. If it bothers them that much I would go ahead and give them an estimate for hammer arrestors and replace the regulator, and write on the estimate that it is an educated guess to an undiagnosable problem with no warranty.

Herk

She says the icemaker isn't doing anything - how does she know? The icemaker does a couple of different things - it empties, which makes the familiar clunking sounds on an empty tray, but at other times, it fills. When filling, it can make a high-pitched whining sound as water goes through the tiny opening in the solenoid valve. Maybe that's what she's hearing.

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smellslike$tome

I should probably clarify here. I used the squealing balloon example because it demonstrated how a small amount of gas in this case air, can make a pretty loud noise. However, the air pressure inside a blown up balloon is far greater than the 2psi gas in the regulator. Furthermore the sound she described in her words was "sort of like the ks faucet sprayer if you turn it on and off rapidly, only faster than you can actually do it by hand" so it's apparantly not really a squeal or anything high pitched but also not a banging or knocking. Kind of a low rapid noise. I have heard water hammer in a variety of manifestations. I don't know how well I am communicating what she was trying to say but it was immediately clear to me that what she was describing was water hammer.

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Putty Truck

Maybe its a washer in one of the anglestops or the faucet.

Are the anglestops on all the way?

With these two sinks, are there two faucets?

neolitic

No great plumbing expert here, but if you are in a hard water area, lime sediment in the water heater will make a kind of banging/thumping noise.
Seems like this happens a while after running a lot of hot water.
It would be mysterious cause it's when the heater is catching up,long after she's turned off the water.
If that's it it could be replicated.
People never drain/clean the water heater.
I'm talking a gas heater here of course.

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smellslike$tome

She has only ever heard the noise when there were NO PLUMBING FIXTURES BEING OPERATED. There could be no water hammer unless water is moving through a pipe somewhere right? She has to be hearing something else that resembles water hammer. I just have no idea what it is. I even spent about an hour cycling through her irrigation system but could not reproduce the noise.

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smellslike$tome

What you are describing is not water hammer but steam. Over time hard water deposits (scale and sludge) will accumulate in the bottom of a water heater. I don't know if you have noticed but you will only hear this popping in a gas water heater thats because in a gas water heater the burner is located under the bottom of the tank. When the sludge accumulates to a sufficient degree the water heater can't operate as efficiently as it once did which for a gas wh was not very efficient to begin with. When you use hot water the temperature falls in the tank, the thermostat senses this and tells the burner to turn on. Now it is trying to heat the water through this layer of scale and sludge which creates very hot temperatures at the botom of the tank. Eventually the water will become hot enough and the thermostat will sense it and tell the burner to shut off but before it gets to that point it will get hot enough in the sludge layer to convert the water contained in the sludge to steam. What you are hearing are these steam bubbles breaking through, sometimes explosively, the sludge layer. As soon as the break through they are cooled by the surrounding water which absorbs the excess heat.

P.S. I checked for this by turning up the heat until the burner kicked on. Ran it like that for several minutes and got nothing.

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neolitic

Cool.
I already knew what caused it.
Once had a home owner describe something similar when I was doing some other work for her.
I happened to be next to the W/H later on when it happened----scared the holy bejeebers outta me!
Figured it out pretty quick when I got about a gallon and a half of lime sediment out of the tank.

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Herk

Yup! We have very hard water here, and I've seen water heaters start popping the lime within two weeks of installation. In very old water heaters, it often sounds like rumbling thunder.

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