I have a Pac-Fab Mitra MA-160 cartridge filter system. The filters deformed on me, so I replaced them with filters made by Pleatco. Unfortunately, they don't seem to fit exactly. Inside the filter assembly, it goes cartridge adapter, big filter, small filter, cartridge adapter, washer, and cap (see http://www.pools.com/parts/Pac-Fab-Pent ... -160_-1724 for a diagram though it's missing the second filter). With all this in place, I can't screw in the cap. So I removed the washer to make it fit, but it seems to keep getting air in the system. So I assume that the washer is necessary, correct? Any ideas on what else I can do? I called Pleatco, and they said everything is in spec. I'm reluctant to try another brand of filters because if that doesn't work, I'm out another $100. Thanks in advance.