I am looking for help. I recently bought a home. During the home inspection the inspector plugged the shower drain, filled the shower to test the shower for leaks. Unfortunately, I believe he used water from the shower vs another source. Within 20-30 minutes water began leaking into the kitchen below through the can lights. (Leak is being conservative, actually was a lot of water coming down). What's more, a puddle of water formed on the front porch, which is at the front of the house whereas the shower is at the back of the house. However, there was/is no evidence of water leakage or staining on the ceiling of the first floor. After talking to several contractors/plumbers all thought it was the shower pan. Well, upon removal of the tile floor and pan, there is absolutely no indication of water damage, stains, etc on the sub floor our surrounding framing material. The contractor is concerned, as he expected to see water stains at a minimum. In addition, given the volume of water coming down and the size of the puddle on the front porch, a lot of water is escaping from somewhere. Anyone have any idea what the next step should be? Could it be the drain? Seems like if it were the supply pipes the leak would be constant.
For any leak, you have to find the source, and also note that leaks travel along surfaces so sometimes where the water is seen is not directly under the leak. Often this will involve cutting up walls and causing more water damage.
You need to find out if the leak is coming from a supply line or waste line, and also when the leak occurs.
First thing - when there is no water running and no water in the tub, is there a leak? If so the leak is before a fixture in a supply pipe.
Now plug the tub and fill it up. While the water is running (but not draining), is there water leaking? If so, the leak is at or beyond the shower valve and possibly in the shower itself. You mention that the leak is pretty big, so if present at this point, stop filling the tub and watch to see if the volume of the leak subsides. If so it could be a leak in one of the shower valve fittings or the diverter stem, or it could be water splashing up and getting behind the tile. In this case your best bet is to open the wall behind the shower (if possible) and look for leaks.
If the water is still running with the tub full but off then the leak is in the drain pan.
If not, pull the plug and check again for leaks. If you see water now, the leak is in a waste pipe. This is the scenario where you can end up cutting lots of drywall to find the source. Start at the tub and go from there, follow the pipe.
If the drywall/plaster is already water damaged, you may as well rip it out before it grows mold - you are going to have to replace it anyways.
I too recently had a leak from my tub/shower. Checked the drain line, cut the walls checked supply lines nothing. Finally found my leak. My tub was not sitting level so the water from taking a shower was running to a corner of the tub and going over the edge of the tub onto my floor. The unevenness of my tub was never noticeable and I always thought the water in that area was from the kids taking showers and splashing the water or not closing the shower curtain properly.