I’m not a plumber but I’m usually handy. Today I’m stumped. I underestimated how over-engineered delta stuff is.
The faucet keeps dripping.
I started by replacing the rubber gasket and spring ( picture attached ) that didn’t fix it. I replaced the whole cartridge with an original delta and the handle now moves extra smoothly but the faucet still drips.
Help! I don’t want to tear up the wall! What else can I try before having to do that?
Videos
How do you know water it leaking back into the wall. I can't quite see from your pictures, did you uses plumbers tape between the copper threads and the new brass piece (three times around, in the direction of the threads)?
I've installed some of these spouts. They never have a set screw. Once the rubber seal is well inside the spout water shouldn't get back there, unless there is a leak between the copper and brass.
The diverter isn't air tight. When water hits the diverter it gets pushed tight making a water tight seal, your breathe can't push it enough to make that seal.
I know of no tub spout that is, or is designed to be, watertight. It is the hole in the wall from which the spout supply pipe emerges that needs to be sealed. This can usually be accomplished with caulking around the pipe, but pointlessly large holes such as shown in poster's photos make that extra hard. Better tile supply vendors sell "rubber" gaskets that grip the spout pipe snugly, but that is something that must be installed prior to the finish surface.