less hot water

[texasmom]

I have a problem that I don't even know where to begin looking for an answer...My master shower, over the last few weeks, has been decreasing the amount of hot water we get each time. It's not the pressure, that's fine. I'm talking about making the hot water last for your whole shower time before it gets cold. It didn't used to be like this so something has changed. We start our showers almost at full hot on the dial and make it quick. The shower upstairs is fine...no changes have been noticed (and my kids take long showers so they would know!)Any suggestions?Thanks

[HayZee518]

check the hot water stem seal. with the hot water hitting the bottom of the valve seat, it expands gradually closing off the hot water feed. replace it - the cartridge.

[jnaas2]

Whay style and model valve do you have, is it a old valve, a pressure balancing valve, or a temperature control valve

[Redwood]

Sounds like it could be several things.
Because you stated dial I'm assuming single handle mixer.

There may be a frozen bressure balancing valve causing a reduced flow of hot water.

There also may be under the handle of the valve a high limit stop that is set too low. Frequently this time of year the cold water supply is much colder than in the summer and requires a larger amount of hot water to get the temperature you desire. If this stop was set during the summer it definitely needs adjusting.