So I started air testing my system and other than a few minor pin hole leaks, I noticed that my one isolation pump flange hisses when I open or close it. It is leaking out of the stem. Does anyone know if I need to tighten the nut under the handle or on top? I am thinking the top one just holds the handle on. I just don't want to damage it. They cost almost as much as the pump. Also, anyone have recommendations as to what I should air test it at? I was thinking 40psi or at the most 50psi. I know air is sneakier then water.