I recently noticed a 6 inch L shaped area of discoloration on the ceiling in my kitchen. The ceiling was slightly damp and soft and it's directly above the corner of my shower stall, so we called the plumber to look at it. He said that the small amount of water that gets on the floor when someone gets out of the shower could be seeping through the grout and the ceiling below. Is this possible? The previous owner put in the tile floor and shower (he owns a floor/tile co) and said that the tile was sealed. Is this a logical explanation or do I need to get the opinion of another plumber?

The leak could be water getting outside the shower if the shower curtain is no completely closed or the door is not closed. It could be a leak in the wall tile grout, it could be a leak where the shower arm screws into the pipe in the wall, it could be a leaking shower valve, it could be a leaking shower floor or it could be a leak in the drain pipe.

Eliminate the water outside the shower by making sure the curtain or door is completely closed and check to see if there is water on the floor after your shower is complete. You can eliminate the possibility of a leak where the shower arm screws into the pipe in the wall by pulling the escutcheon around the shower arm away from the wall ind looking in the hole with a flash light. If you really want to eliminate that possibility, remove the shower head, screw on a 1/2 pipe cap and turn the shower on and look for a leak. To check for leaks around the shower valve, remove the knobs or handles and the trim and look for leaks there. If you have an access panel on the other side or the wall, remove and look for signs of water there. Look for missing or cracked grout in the wall tiles. To completely eliminate that possibility, temporarily tape some plastic up on the walls. That pretty much leaves a leaking floor pan or a leaking drain pipe. If you don' t have an access panel or don't see any signs of water there you will have to make a hole in the ceiling below to see where the water is coming from.

Tile can be perfectly sealed - but you still may get a "leak" because of accumulation of condensation under the tile.

Thanks. We're going to re-seal the tile and replace the rubber seal on the bottom of the shower door to see if that helps.