Two times now I've had a leak in the master bath, falling down into the ceiling in the basement. I had a plumber come out and he couldn't find much. His theory was that the shower had soaked the area outside the tub and it had trickled down. Now the leak is back and it can't be what the plumber theorized, because I was able to stop the leak by tuning off the supply at the hot water heater. It seems to be clearly coming from the hot water line. This is what I thought it might have been in the first place, but I trusted the plumber. Since I have turned the water back on at the hot water heater there have been no leaks. I'm stumped. It can't be a pin-hoe leak in a pipe can it? That wouldn't go away. Might it be a valve?