Pipes Rattling When Toilet Not in Use

Tim76

Hi all,

I recently moved into a house and we have noticed that if the toilet in one of the en-suite bathrooms is unused for a couple a days (i.e. not flushed) then there seems to be a rattling noise from the pipes that connect to it. Don't know if this is the supply pipe or not and it took us a while to even figure out that the noise was related to this toilet. Any idea what might be causing this and is it something to worry about? Once the toilet is flushed the noise goes away and doesn't come back until a period of low usage again.

The house has it's own water supply from a private well so may or may not be part of the issue. Any advice appreciated!

Ger Roe

I am not a plumber .... but, It could be resonance. Water pipes can vibrate due to the pressure of water flowing through them, if their length is equal to (or a multiple of) the resonant wavelength of the water flowing through them. Maybe it has always been a problem in the house, but if your water pressure has changed recently, it could now be that a specific length of pipe is at the optimum length to resonate with the new water flow rate passing through.

The water pressure was decreased in our area some years ago and when it happened, pipes in the attic would sound like they were jumping off the joists. All had been fine for many years before, with the original (higher) pressure flow rate. I knew it was resonance having a technical background, but when the council sent a 'water inspector' to take a look and listen, he had no idea what resonance was.

You could try making sure that pipes are securely held in place so that slight vibration does not start and gradually build up. You could also try adjusting the water pressure as a test to see if a change in flow will move the potential resonant wavelength caused by the water flow, out of the affected pipe length range.

Have a read of this and see if you can do any more detective work :

https://www.fluidmaster.com/toilet-problems/toilet-is-too-loud/

Or... you could call a plumber.

Tim76

Thanks for your feedback Ger, I will have a look into this.