"Foghorn" that doesn't match any usage

[Alinraz]

A few nights ago, my wife and I awoke to a foghorn noise in the house (and no, we don't live next to a lighthouse). It happens at random times and at random intervals, and doesn't seem to corrolate to usage of any apliances or faucets. It lasts about 9 seconds. Due to the randomness and the short time span, it's been very difficult to localize, but it seems to be comming from an area near our water heater in the garage. On the other side of that wall is our downstairs bath (shower, toliet and sink). House is 2 story, about 4 years old, we've owned it for about 1.5 years and never heard the noise till now.

Our gas inlet is also near there. I had PG&E out to look at the gas and they found a large piece of hardened pipe dope in the pipe and figured that was the cause. So we fixed that and then we had no problems last night. In addition, we had someone out to look at the water heater and while he did replace the gas piping (and found more pipe dope) and fixed a minor noise issue with the baffle, he found no other problems.

But, as of ~8am this morning, the noise is back. Happened so far this morning 3 times. I'm at a loss of ideas of what it could be and am getting a bit desparte for a fix.

I saw a suggestion that it could be the ballcock on a toilet, but it doesn't match any usage of the taps or toilets.

 

[Terry]

I would guess that it's a toilet refilling. Checking and replacing the flapper should help the cause.

Why the noise?
It could be the fill valve, the shutoff for the toilet, or it could be a noisey PRV valve.
Sometimes they put PRV's near the water heater where the main water line comes in.

 

[Sponsor]

 

[SteveW]

I had something similar in my old house, where I had installed a pressure-reducing valve but NOT an expansion tank. Periodically, the water pressure would get very high since it was now a "closed" system, and the pipes would vibrate.

If this is the culprit, opening a water tap anywhere in the house will instantly relieve the noise.

If you have a PRV but not an expansion tank, get an expansion tank.

 

[Mike Swearingen]

I believe Terry nailed it.
A foghorn noise like that one is usually caused by a leaking flapper causing a faulty, failing fill valve to run. The fill valve is actually the foghorn culprit.
Replace both, and you'll probably end the mystery.
Good Luck!
Mike

 

[Alinraz]

Well, I don't even know if there is a PRV. I don't think so. The main water comes in to the wall on the other side of the garage from the water heater, and where it goes from there is a mystery. Well, obviously it goes to the rest of the piping in the house, but it goes into the wall and then I don't see it again till it pops out at the various fixtures. But I'd guess that a PRV would be outside a wall and visible, or have an access panel, neither of which exists, so...no PRV?

The good news is I shut the water off to the toilet nearest the noise and I haven't had the noise again yet. It's been 8 hours or so since the last noise, I hope I've got it licked this time.

After a few hours, the toilet tank drained, so I'm guessing we do indeed have a flapper leak. Doesn't surprise me, the upstairs master bath toilet had the same problem shortly after we moved in (though with periodic normal tank refilling noise instead). What had happened there was the gummy gasket they put in had accordioned up a bit and was stopping the flapper from seating properly. I trimmed the gasket ends with a utility knife and the tank stopped leaking. I'd bet I can do that here.

Of course, now the biggest problem is the home builder built the counter out over the top of the tank. Why do they do that? Just to make it harder for a home owner to do what are normally really simple repairs?

Thanks for the ideas and help.

 

[Mike Swearingen]

PRV: A pressure reducing valve should be between your meter and your main cut-off valve, and clearly visible to adjust it or replace it from time to time. Your home water pressure should be between 50-60 PSI. You can call your public water supplier to see what their street pressure is at the meter, or even if a PRV is necessary there. It isn't here.
If you have a PRV, you also should have an expansion tank on your water heater.
Flapper: If your overflow tube has little L-shaped brackets at the bottom, cut the rubber ring out of the flapper and just hook the flapper "ears" on the brackets. Shorten the chain to where it just allows the flapper to close. Works better this way.
Fill Valve: I always use Fluidmaster 400A refill valves. (About $5-$6 bucks at any big box.) Just follow the simple illustrated installation directions that come with it.
Both are very easy fixes, and no more "foghorn".
Good Luck!
Mike

 

[Cass]

I had a similar fog horn once and replaced the fill valve and flapper. I still had the fog horn.

It turned out to be the flexable fill tube between the shut off and the toilet.

 

[Jadnashua]

Note, from what I read, some water meters have a check valve in them, which could cause the same sort of noise if they don't seal properly. It doesn't require a PRV to create this problem if that is the case. A PRV or a check valve creates a closed system. When a hot water tank is partly drained and refilled with colder/denser water. If the system is closed, when that water gets heated, it increases the pressure in the system. This could cause a noise in the prv or check valve at the meter, or if those are not leaking internally (they shouldn't, but do when they get older sometimes), the pressure just keeps rising, sometimes enough to pop the pressure relief valve on the HWH.

 

[JK60]

I had something similar in my old house, where I had installed a pressure-reducing valve but NOT an expansion tank. Periodically, the water pressure would get very high since it was now a "closed" system, and the pipes would vibrate.

If this is the culprit, opening a water tap anywhere in the house will instantly relieve the noise.

If you have a PRV but not an expansion tank, get an expansion tank.

I have a similar noise problem in my house that I've been trying to trace. I do have a PRV. At the risk of sounding completely uninformed, what is an expansion tank, does it replace a PRV, and how does it resolve the pipe vibration problem?

Thank you

 

[Jadnashua]

An expansion tank is a tank with an air bladder in it (sort of like a balloon). You install it in the water line. You inflate the bladder with enough pressure so that it matches the normal water pressure. That keeps most of the water out of the tank in normal circumstances. It also allows room for the water to expand. Now, when the hot water heater causes the water to expand, there is somewhere for it to go instead of forcing its way back through the prv, or checkvalve, or out the pressure relief valve (or a leaky faucet). When you open up a faucet, that water that moved into the tank gets pushed out, making room for the next time. It acts like a buffer for the system.

 

[JK60]

Thank you for the information. It was very helpful!!!