As a Jack-of-all-trades for an apartment complex, I sometimes have to worn stem valves for bathtubs faucets. The valves are made by SAYCO. The valves controlling the hot water seems to fail most. Whenever I need a hot water stem, every hardware store on the planet is sold out. However, they all tell me that the hot and cold stems are inter-changeable. I find myself wondering why are there two part numbers if the two parts are the same. Are the SAYCO hot and cold stem valves the same? If they are not the same, what is the difference between the two?

No, I am not a real plumber.

Sayco stems are fun. They are built cheap and you can change them without removing the escuteon or sleeve. The difference in the hot and cold stem is that the hot stem turns one way and the cold stem turns another. If you had lever handles you could use the cold stem, but since you don't, a cold stem will seem goofy. The thread pattern will allow it to be installed, but the inside thread pattern will make it open and close backwards

Thanls. I think I have seen that goofy behavior when attempting to turn off some bathtub faucets around here.