I can't do this - it takes me several minutes to adjust the shower water temperature to the correct temperature after turning it off. (The difference between bo

I can't do this - it takes me several minutes to adjust the shower water temperature to the correct temperature after turning it off. (The difference between boiling and freezing is like 1 degree of rotation, I'm only slightly exaggerating.) Eventually I'll get a new valve, but right now changing the water flow also changes the temperature.