Need help with a shower leak

[Bfork]

I'm having trouble with a leaky shower. From what we can tell by where the water drips it is coming from right behind the fixures. The only time it leaks is ashen the shower has been on for about 10 minutes. Doesn't leak when the bath is running or draining EXCEPT if the bath is running and you stop the faucet the leak will start. So it seems there is some seal or washer that the shower and bath use that only leaks under pressure. Any ideas where the leak might be?

 

[phishfood]

Do you know what type of tub spout you have?

There are two common methods of tub spout attachment. One is a threaded spout that seals at the threads.The other slips over copper pipe, is secured by a set screw on the bottom up against the tub wall, and is sealed by an Oring. It is not uncommon for that Oring to leak and blow back into the wall.

 

[Bfork]

Thanks for the reply. I'm not sure which kind it is. Ill try and check it tonight