We are trying to open our pool, which has a Hayward Cartridge filter. Our old filter has little plastic parts broken off and broken bands so we bought a new one. After running the filter for about one day, the water circulation had dropped to basically zero. So I took the cartridge out, cleaned with garden hose as usual, and put back in. Still no water circulation. If we take the cartridge out and run everything, we get excellent circulation. If we put in the old cartridge, we get excellent circulation. So this seems to rule out problems lying elsewhere than the cartridge filter. Could the filter be ruined somehow? It is still white, plastic intact, bands intact, etc. Please help - we are stumped!