Soil pipe vibration??

[onwards]

Yesterday I heard a humming noise which became quite loud. I discovered that the soil pipe was vibrating. This vibration could be felt by touching the stack. Also the toilet seats were doing the same.
After a toilet flush it went away, diminishing slowly to a low hum and then no noise at all. This occured a few times throughout the day. Flushing the loo cured it but occasionally flusing the loo started it.

I'm very confused.. Both toilets run into a common outlet under the bathroom floor then to to the external drain in the yard.

I tried Google but got zilch..

What could be causing this please...
TIA

 

[Nige F]

mains water pipe flapping around near/touching the soilpipe - unclipped and full of water hammer Fairly typical work on a new build

 

[doitall]

Change or service the ballvalve.

 

[picasso]

The ballcock in the toilet cistern is causing the water hammer, it might be the pressure in the rising main is high or the mechanism is worn, try replacing the ballcock and see if it makes a difference.

 

[onwards]

Thanks ..
I wiggled the ball valve and the noise went away and has not returned ( 2 months ago)
Good luck