Hi, I need some help fixing my HPA. Here is the problem: I have leak from the tiny hole above the regulator (not the nipple). I believe the oring inside might be worn out but I can't figure out how to unscrew this part. On the newer tank there is a small allen screw that you take off then you can unscrew the bigger part (top of the tank) but on mine there is nothing... so how to I unscrew the top of that tank? It's a pure energy in case that helps. Thanks!