Hi! I have a ticking sound in my wall right around my stink pipe that only occurs when water is running out of the tub. It starts when the water is running and then continues for a few minutes after. I can't seem to see any water leak and the fact that it is just a steady tick... tick... tick leads me to believe it is just the stink pipe but I can't seem to stop it. Any ideas?

What you are hearing most likely's coming from the drain line. Let me explain.
The water leaving your tub is warm. This heats up the drain pipe causing it to expand. When it cools down it contracts. If the pipe's strapped too tight or is jammed against a floor joist it will rub against it and produse the ticking noise that you hear. We have the same complaints from hot water pipes also.
This is harmles and causes no damage. To fix it would involve tearing into walls and most customers opt not to once the mystery's been explained.
Regards, Tom