TOPIC: Fog Horn Noise... What causes this?

I did an inspection today, and when the water was turned off in any part of the home there was a noise that sounded like a fog horn. Does anyone know what causes this. Home was built in 2005.

I have a friends house that does that every time you flush the toilet and it's loud! Single story, 1950's Craftsman home. I always just say it's a ghost Not sure how you'd write that up though!

This was posted on Ask.com:
Often a faulty toilet ballcock (fill valve) will cause resonance sounds like these. At least it's easy to check -- here's how to tell if this is the cause. Close the supply valves to all the toilets. If the noise disappears, open them one-by-one till the noise starts again. Replace the ballcock in that toilet.

If there are no shut-offs handy, sometimes you can locate the offending ballcock by lifting up on the float ball while someone starts an offending faucet.

Another common cause is a faucet washer. If it only happens when using a certain faucet the faucet washer may be loose or damaged. This can cause it to flutter in the water stream causing the various sounds listed in the heading. Try tightening the screw the washer in the faucet stem. If the problem stops and later returns, mash the threads of the screw a little with pliers so they bind in the stem when reassembled. If this doesn't work, then it's time for a new stem assembly.

Speaking of new valve stems, I've also had a third party replacement valve stem cause this problem. In my experience substitute faucet parts often don't work properly. Try to get replacement parts made by the manufacturer of your faucet. If you can't find the parts locally, they all have customer service 800 numbers, and sometimes they'll send you replacement parts free.

Speedy Jim also suggests, "Sometimes a worn out dishwasher/clothes washer solenoid fill valve can cause machinegun like, repeated hammering."  So, if the hammering happens while a washer is filling consider this possibility.

High water pressure can cause a variety of odd problems including these noises. High pressure can also damage toilet valves and other devices connected to the plumbing. If you're on a city water system, ask your neighbors if they are having similar problems.  If you have a well you probably have a water pressure meter. If you don't have one, borrow one or, buy one at the hardware store and check the pressure. If your pressure is above 60psi you may want to adjust your pressure reducer or install one. 

Sometimes pipe noises are caused by the pipes rubbing or bumping inside the walls because they aren't strapped down well or, because their stud pass-through holes are too small or off center. If this is the cause they've probably made the sounds since the house was built or, the wall was repaired.

This isn't very likely, but it may be a problem with the pressure regulator if:

    * your pounding sound happens while the water's running,
    * it happens at more than one faucet,
    * turning on other faucets changes the cadence,
    * the pressure changes with the pounding,
    * and, you have pressure regulator on your main water line

While the noise is happening, check to see if it seems to be coming from the regulator.  If so, the regulator may need to be replaced. 

I hope that helps.

Drew

I'll have to try the test the next time I'm over there!

Check the pressure reducing valve (if there is one).

I don't know what sound your describing, but my house made noises just before the valve went bad.

The sound resonates through the house.

Dave's answer is good, especially if the plumbing is CPVC.  I have had toilets do that and washing machines.  The ball cock is the problem with toilets but not sure what causes the washers.  I have seen the small, test-tube sized copper dealies for washing machines to absorb air before it gets in there.  But, for the whole house, I think Dave may have it.  Sometimes just opening the pressure-reduction valve will solve the problem also, but it is best to let plumbers fool with them...