Why would the shower head spray water when only the tub filler is supposed to be filling the tub

Hi Mac19...

Sounds like the tub/shower diverter is malfunctioning or something is caught up on the mechanism. If you can disassemble the diverter (as in a 2-3 handle tub/shower valve) then do so and replace parts as needed. If you have a tub spout with the diverter integral to that then replace the entire diverter spout as it is super easy and cheap to replace.

Let me know more here if you want...

Mark