Something in our plumbing "hums"

[Ike]

For the past 3-4 years, we have heard an intermittent humming/vibration sound in our house. The sound is loudest in the master bedroom (of course) and eminates from the wall on my side of the bed. The sound is loud enough to hear in most parts of the house. I have gone to great lengths to find out what is causing this sound. This past weekend while replacing the auto-fill valve on our pool I finally discovered how to make the sound stop.

In order to replace the valve I had to turn off the water supply. As soon as I turned the valve, the humming stopped. After replacing the auto-fill with a new one and turning the water supply, the humming returned. Turning off the auto-fill every night so I can sleep is not a solution.

There is a back flow preventer valve on the auto-fill line. Considering the auto-fill valve itself is new, I no longer suspect it as the cause of the humming. So now I suspect it is the back flow preventer valve for lack of a better answer. Has anyone ever heard of these valves making noise? What would be in their design that would cause this?

[Speedy Jim]

Certain brands of toilet ballcock will create this kind of hum/resonance sound.

To prove it, close the shut off valve to the toilet and see if the noise stops. If so, either replace that ballcock or get the mfr rebuild kit.

Jim

[Ike]

I am familiar with water hammer because we use to have a house that had the problem. In this case the noise only happens when there is NO water flow. When the swimming pool auto-fill kicks in, the noise disappears.