I have a skimmer and a main drain, and one return line (another return had been abandoned before we took ownership 13 yrs ago). I have a pent air DE filter, with the pressure gauge on top, that you can bleed the air out of by twisting the cap underneath the gauge.
At the pump there are two lines, one for the skimmer, and one for the main drain. We just opened, and there's a good bit of stuff on the floor that the main drain should suck down. Right now I can't the main drain, I will in a day or so. Anyway, when I turn the skimmer off and have the main drain on full, the pressure drops to 0. Is this normal? I can't seem to bleed the air out of the filter when the skimmer is off and main drain is on. Maybe I'm not waiting long enough, but it doesn't seem like anything's happening. What am I up against?