Over time, the hard water in our area leaves deposits in the moving parts of the plumbing. When our tub spout diverter clogs, I use WD-40 with its spray nozzle curved up the spout to the diverter ...

Q: I have a bathtub/shower combination, and when I pull the knob on top of the spout to start the shower, only a little water comes out of the showerhead while most of it comes out of the tub spout.