I'm connecting this to my overflow. Does it matter which way it goes up? The 50mm pipe just goes in... do I need to seal it with silicone? I know silicone doesn't work very well on PVC
Gaboon, I would fix it as in the pic with the screw part at the top so you can always remove the ball section for maintenance.
Just for interest sake you can reuse pvc joins that have been PVC welded. I have done it often with 20mm and 32mm.
Drill press and a 20mm or 32mm hole saw. and then you just clean it up with sand paper. I have done quite a few.How?