I have noticed that water runs down to the first floor through the light when we take a shower. It doesn't happen all the time. I think we just might need to re-caulk the shower towels. However, now I have a farily large water bubble, not in the same place as the light but a little further to the left. Could it be the water leaking through the shower towels? How can I find the leak that is causing the water bubble.
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Before you can begin to repair the leak you must first locate it. Some tests should be done before you open up the ceiling. Let's start with the drain. Before you go to bed remove the strainer and put some wet rags in a baggie and stuff them down the drain to seal it off. Now run about a inch or so of water in the shower floor and let it set over night. Make a pencil mark at the water level. Next morning check the mark and your ceiling. Water level down? Ceiling wet? No? Then let the water out and check the ceiling again. Still no wet on the ceiling? If the ceiling stays the same then it's a pretty safe bet the shower drain,trap and drain line's OK and the ceiling won't have to be opened up.
This places the leak in the tile grout. Tile grout shrinks over time and allows water to enter above and outside the shower pan where it will run past the pan and leak out onto the floor. To fix this note where the stream hits the tile when you're taking a shower and regrout the tiles in that area.
Good luck, tom

Thank you speedball1. However, does it matter that the shower is in the tub. When we take baths for run water for the tub, there is no leak. Only when we use the shower.

Thank you speedball1. However, does it matter that the shower is in the tub. When we take baths for run water for the tub, there is no leak. Only when we use the shower.
Ah Ha! (Light bulb lights up over head!) You're in luck. Unless it falls down you won't have to open up the ceiling to locate the leak. This places the leak in the tile grout. Tile grout shrinks over time and allows water to enter above and outside the shower pan where it will run past the pan and leak out onto the floor. To fix this note where the stream hits the tile when you're taking a shower and regrout the tiles in that area. Good luck, Tom

Hi All:

Just wanted to pop in and make sure that flowersn220 also remembers to check the shower arm where it connects into the plumbing behind the wall.

Here, you pull the shower arm flange away from the wall and run the shower for a minute or so... look in hole in wall and see if you see a leak at where the shower arm joins the drop ear elbow (see picture below).

If unable to determine if this is leaking by just sliding the shower arm flange away from the wall then you may need to remove the handle and trim plate from the tub/shower valve itself and then run the shower and see if any water drips onto the tub/shower valve from above when the shower is being used.

Anyway... just want you to check the valve itself. Like Tom said, most likely the grout joints... but check the tub/shower valve and fittings above the floor too.

Good luck...

MARK