Ball Valves leaks

[jimdoodson]

When I replace bottom entry and sometimes side entry ball valves,
1. I often get a leak at the plastic -copper joint.
What is the secret to avoid such leaks.
2.Sometimes I also get a leak from the cistern where it exits the ceramic cistern.Once again what is the secret to avoid leaks?
Best wishes
Jim
AKA The Friendly Plumber

 

[Bahco]

1) use a flexi hose or plenty of ptfe tape

2) Use correct donut washer and silicone.

 

[PEDANTICVINDICTIVEMAN]

I like to use a Hep20 tap connecter which has a tapered washer which fits nicely onto the ballavalve tail, never seem to get any probs, anything else use sanitary silicone mastic on everything.