Are you sure the valve wasn't put in upside down?
Most tub valves are meant to flow better to the tub side.
Copper tubing or brass nipples, depending on whether you have sweat connections or IP connections for the tub spout.
I am remodeling my bathroom. Well my buddy the carpeneter is, and I am helping. Anyways, had a plumber put new water lines in for bath/shower. After we put in the tub surround we installed the shower head, tub spout and the single water handle.
We have two problems.
Low water pressure and when you turn the water on with out activating the shower handle it is leaking out of the shower head.
I took the valve back to lowes and exchanged it. We have flushed the lines. The distance from the shower head to tube spout is about 9.5 inches.. so with in tolerance there....
Any ideas??? THanks in advance....