Leaking siphon valve.

[DLCLEVE]

I have replaced my leaking siphon valve and it still leaks on an Arrow outside frost-free faucet around the O ring, anyone ever have this problem?

 

[WorthFlorida]

Are you referring to the nylon washer? If tighten too much the washer or the washer could have been crushed or the O-ring split.
Remove it and wrap some teflon tape around it and the threads.