I am using 3" for the bottom drain and 2" for the rest of the system. So it's ok to run the skimmer to the filter then the pump? Also how do I get water in the system when I start up for the first time? Because won't the pump be pulling air till the water gets there and my in on the filter I built is at the bottom (left side of pic) and out is at the top so that won't ever get water if it isn't pushing water into it?