I want to replace my bathtub spigot, as it leaks when I turn the shower on (not all of the water comes out of the shower head - but some still comes out of the spigot).

I'd read that tub spigots are supposed to just twist off or possibly there's a screw underneath that needs to be removed.

On the bottom of my tub spigot it says ZP and there is a spot that looks like the slot for a very small regular screwdriver, but I'm not sure if it really is a screw to be removed or if it's just some sort of decoration. I've tried unscrewing it, but no luck, which makes me wonder if it's just some sort of marking.

Is anyone familar with this type of tub spigot? Thanks for your help!