As this shower is on the second floor, I was able to check underneath the shower for leaks. I also checked above...none. I cut a piece of drywall out of from behind the pipes looking for leaks...none. This house was built in '66 and the way they did tile in those days was to put up some "chicken wire", mortar over that and then lay the tile. I noticed before the leak appeared that the grout was looking in bad shape especially two or three feet above the floor. I believe this is where the leak was and it allowed the water to flow into the mortar bed under the floor tiles. Once the mortar bed got wet it is extremely hard to dry it out due to the difficulty of getting air there. That was why I used heat. I applied heat during the day for two to three weeks and would check at night for dryness by pushing toilet paper into the cracks. In the morning, I would check the toilet paper for dampness. It finally dried out but now I am unsure because of the coloration of the grout. Like I said the grout is hard but does seem to have a slight "wet" look. Do you think the grout will hold up to showering??