I have an approximately 19,000 gallon pool. It has paramount in-floor cleaners with the optional debris containment canister. We recently cleaned the filters and when we put the pump back on it would only prime when only the skimmer line was on. We have always kept it at 70% main drain line and 30% skimmer line. It does remain primed if I put it at 50/50. However, if I go any more towards the main drain line, the pump loses prime. I have also noticed that air is sucking in from the gray tube by the in-floor cleaning unit into the debris containment canister (don't know if that is normal or not) to where under the dome in the debris containment canister there is air and you can see the water coming form the main drain right down into the basket. What could be causing the pump to lose prime when I try to put it more towards the main drain line? It's never done this before and we've owned it for almost 3 years now. We've had a lot of wind lately with lots of leaves so I tried using a clog blaster, but I'm actually unsure which line to put that in to blow out through the main drain. I have not received any resistance to it.