When I turn on the water (hot or cold) in my tub water starts coming out of the shower head. Everything else seems to work fine. Any ideas?
Thanks,
My shirt is wet!

Check the lift knob it that's what's you have that shuts off the tub spout that makes the shower work. If that's bad and or stuck and not completely open then the shower will do that trickle problem

If lime built up there this also can cause enough restriction to cause that .

If the sub spout is the knob type I would take that off and clean it out or get a knew one if its real ruff.

A reg diverter sends water down first the when that is stopped it goes up.

Like I said I guessing a bit here until I know what action to operate the shower is. So the exact info here from you is needed. If its not the above.

Signed 21 Boat

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It sound like you have a bad spout, Check the images below and tell us which one is your spout in the tub, then we will tell you how to replace it, good luck.

John

When I turn on the water (hot or cold) in my tub water starts coming out of the shower head. Everything else seems to work fine. Any ideas?
Thanks,
My shirt is wet!

Let us know what type of diverter you have. Is it on the tub spout or do you have a three knob shower valve,(see image) Let me know, Tom