I have a 3 knob shower set-up, when I turn on the shower, about 40% of the water still comes out of the bottom into the tub? ZI sthis a bad diverter? No matter how tight you turn the knob it still comes out at 40%.. seems like the knob isn't diverting all the way.. can I fix this myself?

Shut off water to the shower/tub, remove the center stem and replace the washer at the end of the stem, see the image below, good luck.

John

At the same time you have the valve apart check the seat for nicks or rough areas. If you find any the seat must be replaced as well. Good luck, Tom