Leak in the shower is leaking water through the ceiling
I'm Harvey the Master Plumber.
Your problem is: When you use the shower, water leaks through the ceiling.
First, since it only leaks when you're using it you can ignore the water lines. Now comes the detective work. Look very closely at any place the water can squeeze thru, i.e. cracks in grout or caulk, etc. Don't forget to look on the floor imediately outside the shower and around the shower door if any. If found it must be scraped out, cleaned and dryed to get good adhesion, then caulked with a high quality silicone caulk (color of your choise). Any other caulk will crack no mater what they say.
Let dry for 24 hrs.
If you havent found this kind of problem it's time to look at the drain line connection. You may have to open the ceiling to do this, that's why I'm always carefull in the first step. Turn the water on and watch the drain connection. If it leaks there, it must be repaired. In this case you might cunsider checking the Repair Directory for a repairman.
Feel free contact me again!
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Harvey your Master Plumber