So far I'm seeing loads of PTFE being used but I can't see it lasting. I'll try a plastic washer as well or as you say, an o ring. The fit needs to be tight though to stop it being turned the other way.
PTFE tape is fine once it tight enough if you use enough and you get it into position it'll be fine. Who's actually turning taps once in place apart from to turn them on.
So far I'm seeing loads of PTFE being used but I can't see it lasting. I'll try a plastic washer as well or as you say, an o ring. The fit needs to be tight though to stop it being turned the other way.