There is no tightening it. It is dripping from the quick connect end. Not sure if there is an O Ring or ferrule in the valve or if it is just under a bind and leaking. I will pull the lines out of it make sure there is no pulling or pressure on them reseat them to see if it stops leaking. Do not know why they did not put that rascal on 90° elbows to keep tension off the lines.