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Different applications call for certain filters

By Marcelle Dibrell

In the pool and spa industry, permanent filters fall into one of three categories: those using diatomaceous earth, those operating with silica sand, or those incorporating a cartridge filter medium. 

Each has its pros and cons in terms of filtration capability, maintenance, and spatial considerations. So in attempting to find “the best” filter, one needs to be able to define what “the best” means. 

For example, if by “best” we are considering filtration capability or the size of the particles removed from the water, then D.E. might be the best choice. While sand filters remove particles as small as 25 microns, and cartridge filters remove particles as small as 15 microns, D.E. filters remove the smallest particles: 4 microns, according to the Certified Pool and Spa Handbook.

On the other hand, if by “best” we mean “does the job without taking up a lot of space,” cartridge filters might be a good choice. They are also fairly low maintenance.

To continue this line of reasoning, sand filters would qualify as “the best" if we mean “it will last a long time and put up with a lot of abuse.”

According to our recently completed 2013 Service Industry News survey, cartridge filtration dominates the spa filter market in every region of the country. This is reasonable, of course, because cartridge filters are particularly effective in spas and hot tubs and they fit easily on smaller equipment pads. 

When it comes to swimming pools, and as is so often the case in this industry, climatic conditions usually dictate the reason for a preference of one type of filter over another.

For example, sand filters are the first choice of the majority of service professionals in both the Midwest and Southeast, with 88 and 73 percent respectively reporting this preference. 

Sand filters, which are easy to backwash, tend to be popular in areas not affected by drought. 

Meanwhile, D.E. filters dominate the market in Southern California, with 82 percent indicating this preference. While D.E. might not be the best choice for areas affected by drought, the benefit of a high degree of clarity often makes it worthwhile. 

Cartridge filters, on the other hand, are the best in terms of water savings, and are more often chosen for new pool construction. According to our survey, they are most prevalent in Florida and Northern California, with 86 and 74 percent of respondents reporting this as a favorite. 

In addition to the three types of media of which a filter is composed, filter systems are also separated according to whether they operate under pressure or vacuum. In a pressure system, the filter is positioned after the pump, meaning that water is pushed through the filter. These types of filters are more common for residential pools and spas because they tend to be smaller. 

Vacuum systems place the filter before the pump and the water is pulled through the filter. These filters tend to be very large, and are more appropriate for large pools and commercial applications. 

In this issue, look for stories on the various filtration methods commonly used for pool and spa filter systems today. 

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