Mystery pool of water in the bathroom.

Tell her to squirt and keep squirting plenty of washing up liquid into the pan every time she flushes the toilet. If the lip of the pan and the floor is full of suds you have found the cause.

A light sprinkling of talc should reveal where the water is coming from (assuming the floor isn't white).

I had the same thing, It was one or two drops every flush dripping from one of the bolts/wingnuts that secure the cistern to the pan, but there was some condensation as well, and I blamed that at first.

A new close coupling kit, and doughnut sorted it.

Yes, if it's a close-coupled cistern, I would suspect a leaking doughnut

- which allows a small quantity of water to escape each time the toilet is flushed.

Go and flush the toilet a time or two, and have a close look at that area.

More likely to be slight leak between the back of the pan and the waste downpipe. The water will migrate to the lowest part of the floor.

Mr Pounder - good tip. Phil L - we are talking about a couple of pints of water here, too much to be condensation. M...hotmail - I did get her to use custard powder which led me to believe that the streaks left on the side of the pan pointed to it overflowing but the results overall were inconclusive (to her mind anyway).

Graham, Roger, Alan Thank you but the problem does not occur when the toilet is flushed, only when she is absent from the flat.

A leaking fill valve, and no functioning overflow? Just a thought.

OK - how about this. The ball valve doesn't shut off the water completely when the cistern is at the correct level - and has a slight drip which slowly raises the level. This is not noticeable when the toilet is flushed frequently but, if left for a longer time, can reach a level where it overflows. This would have to be combined with a failure of the overflow to carry the water away safely - maybe a leak where the overflow pipe comes out of the side - or bottom - of the cistern.

You could test this by purposely holding the ball-valve down and overfilling it.

But if it occurs when nobody is there, then who flushes the toilet?

I was thinking maybe a leak in the pan which seeps out over time where some water remains in the bottom and if its not flushed a give away would be that this little pool in the pan is empty when the puddle appears. Sadly if that is the cause they need a new pan. May years ago this happened to us here, but the pan was extremely old and if one looked carefully there was a crack in the neck part between the screw down bit and the neck bit. I'm sure there are technical terms for this.

Apart from that are there any other sources of water around, like pipes going up to taps etc that might have a seep and this place happens to be allow point of the floor? Brian

Blocked overflow.

When she isn't around, the cistern has time to overflow between flushes. Try turning the water to the cistern off before she goes out.

Very likely. Could even be overflowing down the back of the cistern if the overflow pipe is blocked (presuming it is the type that needs one)

Maybe someone didn't like it overflowing and blocked the pipe!!!!

How else would excess water from a dripping ball valve escape if not through an overflow. How does the other type of cistern work which doesn't need an overflow? Is it possible/legal for the overflow to drain into the normal outflow from the cistern to the pan? If it is, I'm not sure why all cisterns don't have this sort of overflow.

Clearly you are out of date. Most modern cisterns overflow into the pan and do not need an external overflow (or Warning Pipe as we were told to call them). Most cisterns have a cut away area at the back so that if the overflow is blocked the water will run down the wall - I think it serves to prevent people setting the water level too high.

A lot of cisterns don't have external overflows these days but overflow into the pan. Bad idea if you're on a water meter because you're less likely to notice that it's overflowing.

If they do it now (ie it's not contravening some safety regulation) I wonder why toilet cisterns were *ever* made with external overflows, given that the overflow pipe could always be connected by T piece into the outlet pipe of the cistern to the pan - even in the days before flush-fit cistern/pan connections.

I agree, though, that it makes it almost impossible to tell when the cistern is overflowing and therefore that the ball valve needs some attention.

Someone living in the loft getting a bit careless about tidying up their visit?

Known in Toronto as the 'sweating john syndrome'.