We have an en suite shower and wc situated on the 1st floor of our home. The basin is situated about 3 feet from the toilet. The toilet gubbins is a fluidmaster 400a.
A few weeks ago it started to suddenly refill briefly at all times of the day and night when no one was using it. This would happen up to half a dozen times a night.
I checked the cistern and replaced a couple of worn O rings on the valve body and it was then fine for a day or two.
Then we started getting the noise of rushing water, similar to when you turn on a tap, from the pipework between the toilet and the hand basin. It's weird in that it lasts exactly 9 seconds and only seems to really start during the evening and night.
It's driving us mad - any pointers or suggestions would be gratefully used.