I believe you run your pump/filter long enough to filter all your water once. The amount of time will vary depending on the volume of your pool. I have a 24,000 gallon IG pool so it usually takes me around 8 hours to filter the entire pool. I alter when my pump/filter is on. On days where I don't need to add bleach in the evening, I let it run while I am at work. On days when I know I'll bleach in the evening, I don't run the pump/filter during the day. I'll wait until I get home from work then run the filter/pump until morning.