Backwashing

Make sure you backwash regulalrly. It's amazing just what collects in your filter; it isn't just leaf and wind blown debris that finds itself into the sand of the filter. Insects, suntan lotions, body fats, hairs everything that contaminates your pool filter, so backwashing (cleaning the sand bed) is an essential part of your maintenance regime.
Depending on use and covering, you should backwash weekly.
The optic either on the filter or backwash waste line will appear filthy at the start of backwashing and gradually clear as the filter cleans - normally within 4-5 mins.
It is important to rinse the filter after backwashing or some of the loosened debris and foul water, sturred up during backwashing will flush into the pool. It only takes 30sec - 1min to rinse satisfatcory.
There are water saving pre-filters on the market (look up the cyclone filter probably the best on the market) that helps reduce the debris getting into the filter and use fair less water to flush away. By the installing such items you can extend the backwashing regime.