I have a leaky compression water valve at my toilet.
1/2 copper pipe
Existing value is the compression & screw type valve.
House is 14 yrs old
Contractor used the cheapest of everything when built.

When changing my leaky compression valve and to make this as simple as possible can I use the old compression ring and nut, if it fits?
I do want a quality install.

Or do you recommend that all new valve parts be installed?

Any compromise?

The old nut an compression ring should work with out problem.
To remove old compression ring you will need a faucet and compression ring puller.

When I reuse, I smear a very little skim of plumbers grease on the ring, seals every time.