I have a Pentair Triton II filter, which has the air bleeder and pressure gauge at the top. The bleeder assembly itself is screwed tightly onto the threaded part that comes out of the top, however, it looks like the leak is coming from under the hex nut that secures the threaded part to the top of filter. I have not removed the cover, but I was thinking that maybe there was also a locking nut on the inside top that is loose, because if I remove the bleeder/gauge, the threaded part just turns and you cannot tighten the nut on top. Kinda hard to explain, so here is a link to a short video I shot of where it is leaking. Also, it doesn't leak all the time, only when I turn the gauge to view it, or mess with it. But I have been noticing that when I turn on the pump after being off for a while, the pump is not primed, and air shoots out of the return jets until pump is primed, which may be related to this, or something eles, like the pump pasket ring needing lube or replacement.