Loud Plumbing Noises

As a flush valve begins to turn off, a trombone-like vibration is often heard.

You were on target with the toilet.

Certain brands of toilet tank fill valves will create a "fog horn" (trombone if you prefer:-) sound as the valve closes. The valve closure is actually a chattering which resonates with the rest of the plumbing in the house.

There are repair kits for those fill valves (ballcock) but the novice may be better off replacing the whole valve. Ask at a friendly hardware store or BigBox.

Jim

My house (plumbing??) makes the same sound, but it can be hours since anyone used any water, from any source. The sound was so loud, I initially thought there was some construction going on, right outside my house. The sounds last about 20 seconds, can happen any time of the day (usually twice a day), and "seems" to be the loudest from the basement, under the main floor bathroom. That's what makes me suspect the toilet. But again, it may have been hours since it was last used.

I'm going to try to catch the next noise event in time to flush the main floor toilet, and see if I get a reaction. Any other suggestion??

Thanks in advance

Might try googlin' for water hammer. That's what the banging, groaning, etc. is called in plumbing