air bubbles

I have a going by what the filter say a marineland hot magnum. After I get home from work tommorrow I will rip it apart and go over it very carefully. I never thought to check the orings but that'll be the first thing I check because when it gets tore down for cleaning and filter changes I would suspect that stuff gets in it. All tubing is brand new on itand I do, do the hot water thing (learned it from doing fw) The silicone seal I can get at work because I work in a place that flows 1 million gallons of water in an inclosed chiller system.(also how I learned to build my own chiller) I am also getting air bubbles from where the skimmer water reenter the tank but theres nothing I can do about that since I live in an old house and my floor is off by a good bit. Any way thanks to all for the insight and I hope one day I will be able to help others with there problems like every one here has helped me.