I am guessing it is trapped air…pipes somewhere in our downstairs bathroom vibrate a loud sound several times a day. Just started in the last month or so. ususally when upstairs water is used. we have 2 baths up and 2 down, back to back. Is that trapped air and if so how do I get it out?
* Shut water off to downstairs toilets
* Does water sound go away?
* If yes, turn the water on to one of the toilets.
* does sound return?
* If so, replace the water valve in that toilet.
* Do the same test for the other toilet.
* The rubber of plastic ring that allows water to enter the tank or shuts off the water becomes weak and reacts to changes in water pressure.
* good luck… Adios… Jasper