Our pool is 20years old, we are still using the original pump. It's a cartridge filter, new cartridge installed two weeks ago. It was a disaster when we opened it this year, a lovely shade of hunter green Chlorine, chlorine, chlorine, filter all day (turn it off at night usually, maybe that's a mistake?)and clean the cartridge, steadily for ten days. The chlorine level has been 2-3 ppm, ph is 7.5. It is now a cloudy green, but a much lighter shade. Can't see the bottom though. After ten days of chlorine and constant filtering, I added a floculant and let it sit overnight. All the 'gunk' sank to the bottom and I thought 'hallelujah, I can vacuum it up and be done with this'. Nope. The gunk on the bottom is so fine that as soon as I start the pump it swirls up into the pool again, and today it was shooting out the returns as I vacuumed. There is no 'filter to waste' setting on our pump, I guess because it is so old. So every night I let it sit, every morning the water is crystal clear with a 'rug' of green on the bottom. I start up the filter, grab the vacuum (which I have been just leaving in the pool) and try to vacuum again. Everything swirls up and we're back to green again. I can't get the stuff out! I thought that ten days of filtering and chlorine would manage it. What can I do????