I'm trying to avoid getting a plumber out to my home. My tub spout has never been flush against my wall. Finally, the chaulk gave way I noticed that the spout spun on the pipe freely. I removed the tub spout to take a look and discovered that not only was the spout in need of replacement, aged O-ring, but the pipe was crimped all the way around at the position where the spout should be mounted.
Because of the clearance in the gap the spout cannot be positioned correctly without the spout back washing into the wall when the shower diverter is used. Short of having the entire copper pipe replaced for that section what can be done to fix this problem.
-Rick

P.S.
There are no threads on the pipe.

The O ring is replaceable for a buck and can be greased and installed. There should be a set screw on the bottom side of the spout, is there one?

Like Bob say the O ring is cheap and easy to replace, look at the image will give you an idea how to install a spout, good luck