Swimming Pool & Spa Filters

Many filters were originally installed much too small for the size of pool they filter, and with their deterioration due to age, are just barely operating. Newer filters that have not had regular service will not perform any better than an outdated or undersized filter, and can even cause bigger problems. Regular maintenance is the most important factor in continued performance and reliability.

There are 3 main types of swimming pool filters: SandDE (which stands for Diatomaceous Earth), & Cartridge.

Sand Filters

If your filter requires frequent backwashing (it should be able to operate continuously for a period of 4 weeks between backwashing), the sand may have deteriorated. A properly sized sand filter can go up to 10 years between sand changes. High amounts of oils from swimmers can gum up a sand bed over time. Years of a pump forcing water over the grains wear away the sharp edges of the sand (think about the Grand Canyon). Worn sand becomes circular, and traps dirt less efficiently. The sand in a sand filter is specially graded to trap dirt particles.

Typical Sand Filter

Pool Sand Filter

As a sand filter collects dirt, its efficiency increases, trapping even more dirt. When your pressure gauge shows a reading 8-10 lbs. over its clean, start-up reading, it is time to backwash (forcing water to flow through the filter backwards using the backwash valves or multiport valve) the captured dirt out of the filter.

Diatomaceous Earth Filters

Improperly serviced DE filters may have pressure rise very quickly, and if left without proper DE coating, the grids will become damaged. A properly sized and serviced DE Filter should be able to operate continuously for a period of at least 4 weeks between backwashing.The DE filter is the most efficient type of pool filter. It can trap particles smaller than what the naked eye can see. As with sand filters, the pressure gauge indicates a need for backwashing (forcing water to flow through the filter backwards using the backwash valves or multiport valve) when it reads 8-10 lbs. higher than its “clean” reading.

Swimming Pool DE Filter

Swimming Pool DE Filter

After backwashing a DE filter, a new application of DE filter powder is added to the filter by pouring directly into the skimmer. A semi-annual breakdown of the filter is necessary to thoroughly clean DE filter grids. A DE filter requires a coating of DE powder on the filter grids. This is where the dirt gets trapped in your filter. The powder, when first added, dissolves in the pipe on its way to the filter tank. When it reaches the grids, the powder stops, coating the grid. The water passes on through the powder, then the fabric covered grid, leaving the dirt trapped in the DE powder coating.

Cartridge Filters

A clean cartridge filter element traps dirt and particles of 25-100 microns in size. During routine maintenance, the cartridge must be removed from the tank and washed thoroughly, top to bottom. Each time the filter is cleaned, some of its filtering ability is reduced. The cartridge should be replaced every 2-5 years, depending on the work it was asked to do. If the filter is undersized, and the pool has had some algae and/or tree debris every year (a common problem here in the desert), then it may last only 1-2 years. Correctly sized cartridge filters can operate for 6 months between cleanings.

You can read more about some of the currently available swimming pool & spa filters at a few of our main suppliers (click on the manufacturer names above, just under the title for this page).


30 Dunton Ave., Deer Park, NY 11729

Phone: (631) 242-2667




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