I have right now an intex 18x48" easy set. As normal the stock pump and filter went to s%#t. I got an older model intex 520 filter pump. The skimmer is set correct and always stays in the water never out of water. My problem is after a while like 3-4 hours I can go to the filter canister and blead so air out. Now have an 1hp power flow hooked up to the filter and it still does the some thing. Any ideas? Also is there something I could put in the pump filter to help out the cartrage filter. Looking for a sand filter to go with the pump so someday will have a real filter.