I have the typical shower/tub set-up in my bathroom where you turn the water on and pull the knob to divert water from the tub to the shower head. I get good pressure from my shower head, but I still get a lot of water coming out of the faucet going into the tub. I think there must not be good closure at wherever it is the water diverts, but I don't know enough about what to do. Can I fix a problem like this myself? I imagine it can't be good for my water bill as it is.