Likely cause: the temperature limit stop is set too low

Why this happens

Moen lists three reasons a tub and shower valve will not get hot enough: hot water may not be reaching the valve, a balancing spool may be stuck, or the valve may be calibrated not to allow full hot water. That last one is the limit stop, a small adjustable piece under the handle. It is often set at installation or after a repair and can be set lower than you want.

How to fix it

1. Shut off the water to the shower. Moen says the supply must be off before you take the handle off.
2. Remove the handle and find the limit stop on the valve stem. On Moen Posi-Temp valves it pulls out and reseats in a different notch; Moen Moentrol valves with an integrated transfer valve use a 7/64 inch hex wrench; Kohler Rite-Temp valves use a red and black collar on the brass stem.
3. Move it one notch or setting toward hotter, following your valve's guide linked below. Brands turn their stops in different directions, so do not guess.
4. Turn the water back on and run it at full hot. Check it with a thermometer.
5. Repeat one step at a time until it is hot enough. Stop at 120F or less: Moen and Kohler both give 120F as the ceiling, and CPSC recommends the same.
6. If you have a Moen ioDigital system, check the blue Max Temp Adjustment dial instead. Moen says it is preset to 115F at the factory.

When to stop. If the limit stop is cracked or will not move, or the water is still lukewarm at the last notch, the cartridge is the next suspect.

Start this troubleshooter over

Vent, Valve & Volt is published by the team behind FourHome. Browse all FourHome replacement faucet and shower parts on the FourHome Amazon store.