Water to shower head problem

I don't know anything about plumbing. I just moved into a new place and when you turn the shower on there is a lot of water that still comes out of the faucet. Can I fix this myself and how?

The tub has separate hot and cold knobs with a third knob in the middle that turns on the shower head.

If this has already been addressed, can someone direct me to the thread OR explain it in simple terms.

Thank you!

That third knob is for the divertor. Generally, you can find repair stems for them. But, you'll have to identify the brand and model. A picture may help.

From a long-term resale and safety standpoint, it would be better to replace the system with a new valve that meets the current anti-scald rules. It is okay to repair the old one from a code standpoint, though.

quote;From a long-term resale and safety standpoint, it would be better to replace the system with a new valve that meets the current anti-scald rules. It is okay to repair the old one from a code standpoint

From a resale standpoint, I do not know many people who would prefer the looks of a "remodel plate" in the bathroom over a three valve diverter, although the one I use, because it is part of a single valve faucet does not look like a handyman job.. Repairing or replacing the diverter would be immensely cheaper, also.

Some new homeowners, especially if they have children, and if the home inspector points it out, will ding the property if it doesn't have the currently required anti-scald type of shower valve. Some remodel plates look better than others.