Ron, the screen gives you more surface area. Without it, debris would fill the outlet quickly. The fitting has a o-ring on the inside portion. When the nut is tightened, it pulls the fitting down and seals the bottom. They use Lock-tite on the threads, thus your loosening problem. I have been able to get them apart by holding the nipple and slowly turning the nut. If the nipple is spinning in the fitting, cut it off and try a airgun. The Loc-tite was and is a stupid idea, and I never use it for this application.