I have a single handle (cartridge style I believe) delta tub/shower setup. The faucet is leaking after a shower but does not leak after running just the tub only. Any thoughts on what this could be?
So it doesn't keep leaking indefinitely I assume, or you wouldn't know that it doesn't leak after using the tub because it would always be leaking continuously.
My assumption is that because your faucet is much lower than the shower-head, the water left in the pipe that leads to the shower-head is slowly dripping out after you turn off the shower. Mine does this too but it comes out quickly. Try turning the adjustment back to the tub faucet setting after you turn off the shower. If that doesn't work, try turning the tub faucet on briefly after a shower (this may create a siphon and pull it out more quickly)
Truthfully, unless it leaks continuously for hours, I wouldn't worry about it. If I am correct in my assumption, you're not losing running water, only after left in the shower-head pipe. And only continuous drips could eventually erode the ceramic coating on a tub. A few brief drips after a shower should not.