: The "standard" choice. It keeps water temperature steady by adjusting pressure. It prevents "toilet-flush" shocks where the water suddenly turns scalding.

: Necessary if you have both a tub and a shower. It directs the water from the tub spout up to the shower head. 2. The Compatibility Trap

: The "luxury" choice. It lets you set a specific temperature and maintains it regardless of pressure changes. These are ideal if you have multiple outlets (like a rain head and a handheld wand).

: If you want flexibility, look for "Universal" rough-in valves like the Delta R10000-UNWS , which works with most Delta trim styles. 3. Shopping and Installation Secrets How to Install a Shower Valve Kit (For Beginners)