Our toilet flushes when next door use theirs

[d000hg]

I'm sure this never used to happen, but we've noticed sometimes when next door are flushing their toilet (or using their taps, you can hear it through the wall when it's quiet), our downstairs toilet does a sort of half-flush on its own.

We're a bit worried how this could happen since we have separate mains and they're new houses (not one big house that got split into two for example).

Can anyone explain what might be going on, and if it's something we need to worry about - we're both on water meters.

 

[longdogs]

I am assuming that your toilet doesn't actually flush but lets a certain amount of water into the cistern, so it's the filling noise that you can hear. It might be a problem with your fill valve if it is of the equilibrium type. Pressure needs to be of equal pressure both sides of the valve for it to shut off. So when your neighbour flushes, the pressure behind your valve reduces slightly and remarkably, lets some water through at the same time. (even though you are on separate meters.) This can possibly be fixed by fitting a new fill valve and if necessary fitting a non return valve in the pipe before the fill valve.

Personally, I would try changing the valve first and see if that solves it.

 

[d000hg]

Thanks. I've only seen it happen once, but some water definitely came into the bowl as if we'd tried to flush the toilet when the cistern was empty is the best way of describing it. However from what you've described, that might simply mean the cistern is over-filling as the valve allows water in, and this just overflows into the bowl? It looked like if you

 

[JohnD]

it's important to know if this is happening in the bowl or in the cistern.

For example, if there was a blockage in the soil pipes or drain, the pressure change caused by flushing one WC might cause the water level in the trap to go up or down. This would be quite serious. Have you got a "man-hole" cover?

 

[d000hg]

Definitely we see water falling into the bowl from the cistern, not just the level in the cistern changing - and you get the sound like water going into the cistern too. So it sounds like squeaky has the most likely explanation?

 

[JohnD]

take off the cistern lid so you can see what's happening.

 

[d000hg]

take off the cistern lid so you can see what's happening.

I'll maybe ask our neighbours to go round flushing their toilets while I stand and watch ours, to see what sets it off and what happens

Thanks for the tips, good to know what to look for.

 

[Rampage77]

It could have an internal overflow pipe, which lets the water overflow into the pan.