Porous WC

The best way to tell if you have crack in the bottom of the bowl is to feel around with a finger nail. Your finger tip may always pick up a hairline crack, but a finger nail will feel it better when it sticks in it. Vitreous china is used on these appliances because it can be so thin and un-glazed and still won't become porous. A web search on the subject will give you more information on it.

You may also have condensation running down from the bowl and the cistern on to the floor. If the water in the loo is cold and you've just filled the room with warm moist air, then you'll get condensed water on the outside of the china. This has to drip off somewhere if not wiped off. I honestly think this is what you're seeing, because you say it's only occasionally happening.

with the aid of a torch get down to ground level and check all conections when flushed.it can be a small leak from the joints that is accumalting

Yes, or alternatively a leak in the flush system or waste pipe that only shows up after a flush.

I had those (both types) and they are the devil to find.

Just drop one of those dye blocks in the cistern. If something is leaking it'll leave a trail.

Lee

Now why did I not think of that?

Thanks all. I'm feeling more optimistic and determined now and I'll try the various suggestions. Meanwhile it's not leaking again :-) or is it :-(

Another Dave.

I have had to change a toilet for someone which they bought at b 'n which did appear to be porous, certainly it needed changing, when removed it I was able to prove so. B 'n q replaced it and payed m labour charge back to the customer

-- Paul Barker