Cartridge filters:
Turn off the pump. Remove the filter, hose it off, and soak it in detergent according to the manufacturer’s instructions for removing oils. Repeat every three to four months..
Sand filters:
Turn off the pump. Circulate water through the filter in the reverse direction for about 10 minutes, a process known as backwashing. Repeat once per month.
Diatomaceous earth (DE) filters:
Turn off the pump. Backwash the filter (see above), then add more diatomaceous earth to the skimmers. Water will carry the D.E. to the filter and recoat it. Repeat every three to four months.
What kind of filter is better? My filter is old and I think it needs to be replaced soon.
Cartridges filters do wear out and need to be replaced every few years. Their filtering ability approaches DE in particle size filtered out (as low as 10 microns.). Sand is by far the easiest to maintain but its filtering ability is the lowest – down to about 30 microns. The most effective filter media, is DE (diatomaceous earth). DE is made up of fossilized diatoms (porous, sponge like microscopic organism) and can filter down into the 3-5 micron range.
Any filter type you choose is going be a compromise between filtering ability, ease of maintenance, and real estate taken up on your equipment pad.
I prefer a cartridge filter as they are the most user friendly filter. However there are still going to be people who prefer the clearest water available (D.E.) or the system with the least amount of maintenance (Sand). It all depends on what your needs are based on, the environment the pool is located in, and your preferred level of maintenance.