SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

If the valve itself, or the diaghram is giving you a problem. You can swap the guts out between a new/old one. If its the body and threaded connections, then you will need to remove the old one first.

Pictures are worth a thousand words........

Working on the PVC side would be easy. The metal/copper is where you are going to do 80% of the work if you need to replace it. The copper male thread into the plastic female thread is a common no-no. Cold/hot expansion and contraction will break the plastic threads if they are tightened too much. It should always be plastic male INTO metal female. This is probably why it is leaking.

Let me throw in my two cents. The valve in question is a jar top. That model in particular is famous for leaking. Sometimes you can just tighten it and it'll stop leaking. If not replace the whole thing. I've had nothing but bad luck trying to keep one of those things from leaking once they've started, even with a whole new bonnet and diaphragm.
When you unscrew the valve just make sure the metal pipe is stable. Make sure it doesn't turn. What I mean by that is sometimes the manifold is plastic with a metal nipple screwed into it. You can break things if it is. If the manifold is also galvanized then no worries.
If you don't have room to unscrew the valve, simply cut it in half.
Use a wire brush on the metal threads. Use teflon tape and install the new valve.
PS. Please buy a different model valve. The 2711APR will do the trick.
2711 < click on that.