DE filters remove even the most minute dirt particles that normally pass through sand - it even removes dust and pollen! The exclusive Perflex "bump" system gives you long filter cycles between backwashing. Simply "bump" the handle to redistribute DE and you are ready to continue filtering. When DE is redistributed backwashing is reduced and DE is recycled, saving hundreds of gallons of pool water and saving you time and hassle. Maximum pool size 38,400 gallons (based on 8-hour turnover rate). 7 lbs. diatomaceous earth required (not included).