We are installing Delta front-cartridge thermostatic shower valves in a new shower construction. Plumber insists that the shower valve has to be relocated to the back wall of the shower (requiring the user to either step in and get a cold shower until the water warms, or get a wet head and shoulders) because an access panel is required behind the valve. Well, there is nothing behind the valve body but a 2x4. All connections are on the sides, top and bottom of the valve body. The relocation now has many more potential points of leakage due to PEX elbows and clamps, and none will be accessible through the access panel. Thoughts? Does code REQUIRE an access panel behind a valve that has no rear serviceable parts? And no, it's not for shutoff access. They didn't install any, and the access panel is right behind the valve.