Pool Filters - How They Work and How To Choose the Best One

by Pool Builders on 01-31-2008 in Articles

Pool filters are an important and necessary element of any pool's circulatory system. The filter acts as a physical barrier between the water and pump system - literally filtering out garbage, leaves, and other debris from getting into the plumbing and causing plugs. The better the filter material - the smaller the debris it catches.

A pump pushes water from the pool into the filter, which uses one of three porous materials to cleanse the water of algae, dirt, and bacteria particles. The pump then circulates the filtered water back into the pool.

Each pool has different specifications that determine which combination of pump and filter is the most effective for every shape and volume. It's worth it to have a professional do the math and ensure you are buying the right size pump and filter.

The three main methods of filtering are:

  • Sand - The water is taken into a series of chambers bedded with sand. The top layer of sand traps the particles and the filtered water exits out the bottom of the sand layer. When the sand becomes clogged with debris it has filtered, pressure builds up and results in a loss of flow. The process to clear out the used sand is manually performed on a weekly basis. It is called "back flushing". Simply put, run the filter in reverse and get rid of the waste water. Sand for pool filters is specially graded to catch particles in the 20-100 micron range. This is considered a bit low by industry standards.
  • Cartridge - Cartridge filters are the low-maintenance and least expensive way filter method. One cartridge filter should last an entire pool season. Cartridges are made with the same material used to make sink filters. These filters have a notably larger filter area than their sand counterparts. Most cartridges begin at the 100-foot size, but the most popular size sold is in the 300-foot range. They also run at a lower pressure than sand filters, so there is less demand on the pump and no issue with flow volume. Cartridge filters are easily cleaned with the spray attachment of a garden hose. It's as easy as pulling the filter out of its housing and spraying off the dirty part - usually only a couple of times per pool season. Particle-wise, the cartridge filter performs in the mid-range between sand and DE filters.
  • Ditomaceous Earth (D.E.) - Uses a naturally occurring material to render pool water brilliantly sparkly. D.E. has a sand-like quality to it, but works much harder. D.E. achieves the best micron filtration rating -it cleans pool water the best by filtering even the smallest particles. D.E. appears to have more of a powder consistency than sand. Under a microscope, the powder appears to be a gathering of microscopic sponges. This is how the powder works as a filter - pool water is drawn through the powder and "cakes" onto the gridded support structure. D.E is actually composed of the microscopic skeletons of ancient, sub aquatic organisms. The inexpensive powder is available anywhere pool filters are sold.

All filters work well. Which filter you choose depends on what how you want it to perform. Sand is a great choice if you want an indestructible filter. Cartridge is ideal for low maintenance. DE will make your water the cleanest and make it sparkle.

Some pool experts say you can add a little DE powder to a sand or cartridge filter to bolster its ability to filter smaller particles. The ultimate pool filter, then, might be a cartridge filter with some DE added for sparkle.

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