If your looking for a ball valve go with the dip tube. Then you can turn it to get above the yeast line. How are you going to be adding priming sugar?
http://www.norcalbrewingsolutions.com/store/Speidel-Fermenter-Dip-Tube-NPT-Male.html
Cheers
Jay
I bought a dip tube for my 30L a while back and I was surprised how big it it. With nothing in the vessel, i got it set up with a ball valve, but couldn't figure out how transfers would work since this thing wants to point directly down. I'm sure its great at getting a lot of liquid, but my hoppy beers usually have a trub/yeast line that is pretty close to the height of the valve. With the OG plastic valve you can rotate it a bit, but does not gain you too much. Lately, I've been tilting the fermenter for the last 4-5 days to keep the sediment away from the valve so I get a cleaner transfer.
The way the threads were created, it makes it pretty awkward if you want to point the dip tube up, the valve handle will be upside.
Im very curious how others with the dip tube have overcome this problem? Maybe it isnt a problem, and Im just worried about nothing?