I am assembling a 1 1/4 inch pressure tank tee and using PVC nipples instead of galvanized nipples to connect the brass fittings (check valve, ball valves, tank tee etc). I am not that familiar with PVC threaded nipples and would like to know how far to tighten them for leak free connections. The same as galvanized, two or three threads showing after tightening? Any danger of cracking or shearing these nipples? I am familiar with the danger of using male metal nipples into female PVC fittings such as a union where there is a real danger of splitting the female fitting by over tightening but what about the other way around - male PVC to female brass? Should I just forget about corrosion proofing and stick with galvanized nipples?