: My antisiphon outdoor faucet is leaking out the top cap. The cap spins, but does not unscrew. How do I get the cap off to repair the inside mechanism?

Madge,
The design is poor in my mind.
Most of the time, the cap can be removed with pliers, sometimes the cap will break somewhat.
The part below, will unthread, exposing a floating piece with a rubber seal. I have seen repair parts for these also. Terry