Pool Filters

There are three main types of swimming pool filters: D.E. (which stands for Diatomaceous Earth), Sand, and Cartridge. By filtration, the order would be D.E. first, then cartridge filters, then Sand. However, the suitability of a filter to a pool can have more to do with size, than with type. Always go at least one size larger than you think you need. Buy the largest filter you can afford, it's money well spent. In pool filters, size matters! Let Lake Norman Pool and Spa help get you into the right pool filter to help keep your pool water sparkling clear. We carry all the major brands and many filters in stock or we can get the one you want.

D.E. Filters
Diatomaceous earth is mined and is the fossilized exoskeletons of tiny diatoms. They are used to coat “grids” in the filter housing and act as tiny sieves to remove debris. They are very small and as such can filter out particles as small as 5 microns. Diatom filter area are sized between sand and cartridge – around 60-70 sqft are most common. Once the filter pressure rises, the filter is backwashed just like a sand filter and then “recharged” with more DE powder. Typically it is poured in a slurry into the skimmer and it then coats the filter grids. DE filters run at higher pressures than cartridge filters and as such can lead to some inefficiency and flow loss.

Sand Filters
Water is pushed through a bed of filter sand and removed through a set of lateral tubes at the bottom. The filter area of a sand filter is equal to the area of the filter itself. For example, a 24” filter will have 3.14 sqft of filter area. Only the top 1” of sand is actually

used to filter the water. The principle behind this filter is that water is pushed through the filter sand, somewhat like an espresso machine. Dirty water goes in the top and clean water exits out the bottom. As the filter sand becomes plugged with debris from the pool, the pressure increases on the filter and the water flow drops. In order to clean the filter, you just run it in reverse and dump the waste water; this is referred to as “backwashing” the filter. This has to be done manually when pressure reaches 8 to 10 Lbs above normal operating pressure. Once the filter is backwashed, you move to the rinse mode and that repacks the sand and then back to filter. Should the sand ever become really dirty, it is easily and inexpensively replaced. In terms of particle size filtered out, about 50 – 100 microns. Also ask about better filter media such as “ZeoBest”. It replaces the sand and filters much tighter than regular pool grade sand.

Cartridge
This one is easy to understand. Water passes though a filter material and the filter captures the debris. This is just like the water filters used under your sink. Cartridges have much more available area to filter than sand. Most start at 100 sqft and the majority of the cartridge filters sold are larger than 300 sqft. So they don’t clog up as quickly and therefore you touch them less frequently. Cartridge filters are designed to run at lower pressure than sand. This puts less back-pressure on the pump and hence you get more flow and turnover for an equivalent pump size. These filters have to be cleaned once or twice a season by simply applying Kleen-It filter cleaner and then hosing them off, so you don’t touch them as often. You can also soak the filter then hosing them off. In terms of particle size filtered out, cartridge is somewhere between sand and DE, approximately 10 – 30 microns.