Shower Single Handle Leak

I have a single handle shower valve that is leaking. I do not know the model, but the outer plate is stamped delta. My problem is that when I turn off the water and take of the handle, I am not sure how to proceed. I tried to turn the knurled ring, but it is real tight and I don't want to torque the valve off form the piping behind - there is a chrome space behind the knurled end that turns freely, so there is no way to generate opposite leverage to protect the piping. There was a horseshoe clip that I also removed, but could not pull off the heat control piece (the one with the set screw in the picture).

Can someone identify this setup and tell me the best way to fix. Thanks!

Looks like a Delta 1600. Here is a breakdown of the faucet

Here is the cartridge. Readily available at plumbing supply stores.


You do have to be very careful unscrewing the cap nut. You can destroy the valve by breaking 3 little tubes which connect the body to the manifold. This will be a BIG problem.

Try soaking in white vinegar or PB blaster. Try adding heat from a torch, tapping a little, etc. Sometimes it will be necessary to slice through the nut with a dremel. The nut and other parts are still available, so don't fret over damaging it.

Sorry , not able to post links to commercial websites, but you can find the info with a google. Just look for Delta 1600.