Two months ago, we installed a new stone tile shower -the contractor installed a lead shower pan along with cement bed. Tiles were installed using thin set + Laticrete Superflexible Adhesive; tiles/grout were sealed with 511 impregnator. The shower drain recently backed up creating a 1-inch pool in the shower - the pool did drain, but also leaked into the ceiling in the floor below (quite a bit of water leaked through - say 5 gallons). We removed the clog with a long snake and then tested for leaks - after running water for quite awhile, we found no further leaks. However, I find it odd that a backed up drain should cause such a leak -> is this normal/to be expected? Any suggestions on how to tackle the problem?

We quit panning our showers with lead back in the seventys. It was too easy to slip and poke a hole in it. We used Compatite and later Blue Brute heavy plastic for our shower pans. Several things would cause the leak you describe. Perhaps there is a small hole in the lead pan or the weep holes were blocked by mortar, Could be a bad connection around the trap that only shows when the line is backed up and full. Any way you look at it the shower should hold and contain a one inch head of water and not leak it out. I would get the contractor back and have him find and repair the leak. In our new construction we block off the drain before the tile man starts to tile and run a few inches of water in the pan and let it set to see if we had any leaks before any more work is done. It's apparent the contractor failed to do that. Leaks can only get worse, they never heal themselves. Don't let the warranty, (You DID get one didn't you?) run out before you complain. Call him back to do the job right. You may want to block off the drain and fill the base with a inch or so of water and let it set just to make sure the leak's in the pan and not in the trap or drain line. Good luck, Tom