I have a leak coming from my 2nd floor bathroom tub/shower into the ceiling of the familyroom below. I can run water and fill the bathtub-no leaking occurs. I can drain the water from the bathtub and no leaking occurs. I can pour water over the tiles around the tub-no leaking. But when I run the water and activate it so that the water flows into the shower head leaking occurs. I have resealed around the tub and around the tub faucet.

Judy08...

First thing is to take the chrome flange around the shower arm and move it forward...

Then, run the shower and using a flashlight see if you can see a leak at the threads where the shower arm joins the pipe behind the wall.

If nothing obvious after that then I want you to remove the handle from the tub/shower valve and remove the chrome trim plate around the valve body itself. Once chrome trim is removed you need to turn valve on and fluctuate between tub and shower and see if you can see any leaks behind the wall...

You should not need to shut the water off to remove the trim...

Let us know what you find...

MARK

Mark has you looking at the only two possibilities based on your detective work. My bet is on the pipe coming up out of the mixer.

Also, make sure your tub overflow cover is not loose or turned bottom up - as many people do to get more water into the tub...

Milo,
Did you miss this?
I can run water and fill the bathtub-no leaking occurs. Regards, Tom

Tom, thanks for asking: No, I didn't miss it...

When you running shower, water hits overflow plate from above. If overflow plate is loose, and turned up, it will produce a leak.

Never saw a overflow plate turned up side down to gain a inch more of water but the way you describe it could happen. Thanks Milo.