Normal, periodic rinsing or backwashing will remove most of the dirt from a basically clean filter. However, over a period of time, grease, oils and scale can attack and build up on the elements. When this occurs, you will see build up on the removable elements, short filter runs, reduced circulation and water that does not want to clear up.
 

The sand stays in the filter for a long time. Five to ten years if you are using chlorine. If you use a biguanide sanitizer, you should have the sand changed every 3 - 5 years. Believe it or not, a sand filter works better when it's dirty, so it's important not to backwash it too often. A clean sand filter will trap a particle 50 microns in size, while a dirty sand filter will trap a particle only 20 - 25 microns in size. Sand should be chemically cleaned at least once a year, twice if you're using a biguanide sanitizer.
 

The filter system should run for a minimum of 8 hours every 24 hours.
 

The frequency of backwashing will depend on many factors including the size of your filter, flow rate of your plumbing, and bather load in your pool. You will know your filter needs to be backwashed when the pressure reading on your filter reaches the specified level (as set out in the filters manuals guidelines). Whenever the pressure reaches this level the filter should be backwashed. It is ususally 10-15 psi higher than the psi when the filter was new of just thoroughly cleaned.

The filter should be backwashed at least weekly and whenever the filter gauge reads 10 lbs. higher than what it does after backwashing and rinsing the filter.

 

Usually it is adequate to change the D.E. once every 30 days. However, if your pool water is very dirty it is not uncommon to change it 3 - 4 times a day until the water is clear.