Bazooka Screen Wort loss

I have just purchased a Bazooka screen to use for mashing and wanted to know the amount of wort loss when draining threw a Weld-B-Gone. If it is dependant on the height of the ball valve, I haven't mounted it yet so any suggestions would be helpful.

It absolutely depends on the height of the ball valve. Try to get the ball valve opening as close to the bottom of the cooler as possible to minimize wort loss. If your cooler has a depression in the center that leads to the drain (or where the drain would be as some coolers do not have a spigot installed), you might want to put the valve slightly higher, so it is easier to screw on. Bazooka Screens aren't very flexible at the threaded end.

You can build a dip tube with a compression fitting that's threaded in both directions and insert it into the Bazooka if you want to get every last drop. Not as big of a deal for MLT as for a boil kettle, but easy to do.