Pooling water on bathroom floor tiles

[fezster]

A bit of a long shot, but hoping for some ideas on how to investigate this. I'll try and post some pictures tonight, though not sure how helpful they'll be.

I noticed a small pool of water in my downstairs bathroom a few weeks ago. Cleaned it up, and noticed it again last week (Friday). Cleaned it again, and then have been monitoring daily. Last night (Mon evening around 11pm) it was clear, but this morning at 7am, it was there again.

There is a shower right next to the water which has not been used (for many months). The pool is outside of the shower tray. The pipes leading to the shower are underneath tiles where the pool of water is forming. The floor underneath the tiles is concrete. Given the water did not appear for 3 full days, I'm inclined to think it's not a slow leak from the hot or cold supply pipes to the shower. Even if it was, would it appear from beneath the tiles? There is no cracking of the grout or other visible sign of disturbance around the pooled area. The walls are also not wet and the ceiling does not have any signs of water damage (there is a bathroom above also so possible water was leaking down from it).

Not sure how to investigate this further and because it took 3 full days before it reappeared, not sure how I can monitor it? Any ideas?

 

[oldbuffer]

1. Large sheet of paper held off the floor as far as possible up to bath height. Pile of bricks, couple of chairs?
2. If paper (eventually) gets wet, leak from above. If not, and pool reappears, leak from below paper level.
3. Check water inlet to WC. I've had the inlet threaded shanks (white plastic) crack. Fine all day, until pressure goes up at night (if mains fed) when crack opens like a valve. Then closes up again.
4. Check water inlets (hot and cold) to wash hand basin.

 

[fezster]

Thanks for the suggestion. There's no bath in this bathroom, but I'll try and put something up floor height to cover water falling from above.

The house has a 3 bar pressure reducing valve on the incoming main, but I'll go around all of the accessible connections to see if any are wet. It's strange because aside from where the pool is, I can't see water having traveled anywhere else (either down walls, or along floor from where the toilet and sink is).