“FILTER TYPES” and the importance of “FILTER EFFICIENCY”
The importance of filtering efficiently cannot be stressed enough, especially when swimming pools are subjected to extreme summer temperatures. The following information will help you understand the various types of filters available and the efficiency of each one.
The efficiency of pool filters are rated by how well they can remove Micron size particulates from the water.
Listed below are the three types of pool filters, from best to worst.
D.E. (Diatomaceous Earth) filters can remove anywhere from 1-5 microns in size
Cartridge filters can remove anywhere from 10-15 microns in size
Sand filters can remove anywhere from 20-60 microns in size
Most of the algae and bacteria in swimming pools range anywhere from 0.1 to 15 microns in size. Please note that the filter that can remove the smallest of micron size particulates is the more efficient filter.
Pools that have a tendency to turn green, especially when there is chlorine present in the water, can be directly related to the inefficiency of the filter. This means that your filter is not able to remove these small strains of algae from the water, even though you may run it 24 hours per day.
Listed below are the Advantages and Disadvantages of each of the filters:
Here are three cut-away views of the various pool filters. From L-R, Cartridge, DE, and Sand
D.E. filter: Advantages
Maintains the purest water with the highest clarity
Removes virtually any and all bacteria from the water
Requires backwashing when pressure rises 10 lbs above normal reading, which generally takes several months, thus conserving hundreds of gallons of water
Will clear up green or cloudy pools overnight
Must add D.E. powder through skimmer after backwashing
The powder leaves a white residue on the ground after backwashing, but will disappear after soaking or rinsing with water. It will not harm the grass or ground
It is recommended by the manufacturer to remove the elements inside the filter and clean annually
Cartridge filters: Advantages
Maintains good water clarity, but not as good as a D.E. filter
Removes several strains of algae in pool water but not all
Does not require backwashing
Cartridges only need to be cleaned when the filter pressure rises 10 lbs above the normal reading. This may take a few months depending on the pool.
Takes longer to clear up green or cloudy pools than D.E. filter
Since cartridge filters do not require backwashing, you have to remove them periodically and clean them.
To clean cartridges, top of filter must be removed, and each cartridge must be separately hosed off. It will take approximately 1 hour to clean all the cartridges.
When the cartridges need to be replaced they are expensive
Sand filters: Advantages
Ease of use and backwashing
Needs to be backwashed more frequently wasting hundreds of gallons of water.
Maintains the poorest of water clarity compared to the D.E. and Cartridge filters
Filter needs to run more hours per day to make up for its inefficiency
Generally takes two or more weeks to clear up green or cloudy pools, and in that process filter clarifiers generally need to be purchased to help the sand remove the finer strains of algae from the water
Removes very few strains of algae in water, thus allowing the pool to become infested with algae and turn green, even when chemicals are perfect
Sand needs to be changed about every three to five years
Often times allows dirt, algae, and other impurities to pass through the sand and return to pool after backwashing or while vacuuming the pool. This cloudy water can be seen where the water returns to the pool.