I have excellent water pressure, but lately after I have adjusted the bathtub water to the right temperature and then pull the shower knob, more than half of the water is still coming out of the tub faucet instead of the shower head. Consequently the shower water pressure is minimal and it is impossible to get the right temperature. It's either too cool or too hot. Can I change the shower pull knob thingy myself or does it require a plumber?
Thanks,
Laura