Delta shower valve body is clogged. (water barely dribbles out shower arm, regardless of valve setting - cold or al the way hot) Tried all the usual back pressuring etc. including removing the cartridge mixing chamber valve seal insert piece, and turning the supply back on with only the cap re-installed. The internal port connecting to the vertical pipe going to the shower arm is plugged. It appears that only a 1/4" flexible hone or ream could possibly access the point where the blockage is. Tearing apart the tiled shower wall to replace the valve body (Rough-out) is not an attractive option!

Also - a flexible tube was run all the way down the vertical pipe feeding the shower arm, from the elbow where the shower arm is threaded, to 1" from the valve body centerline. Therefore the passage was clear, literally all the way into the valve body itself.

I doubt the pipe is clogged. Remove the cartridge and then turn the water back on (cartridge still out) and see how water flows... if good pressure/volume of water, replace they shower valve cartridge. If not good pressure/volume, post back again, OK?

Mark