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How to Choose the Right Pool Filter

Written by Rochele Walton of Wise Pool & Spa Service, Inc.
Updated June 15, 2021
Swimming pool
Consult your pool professional for help determining which filter suits your needs, lifestyle, and budget best. (Photo courtesy of Wise Pool & Spa Service)

There are three basic types of pool filters - which one is right for you?

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Before you can decide which type of pool filter will be best for your situation, one thing you must understand is what a micron is. A micron is a unit of length equal to one millionth of a meter. To compare, a grain of salt is about 100 microns, bacteria typically measure two microns or smaller, and decomposed algae is one micron or less. 

The three types of filters outlined below can only filter out particles and debris up to a certain micron each. Let’s take a closer look:

Sand Filters

Sand filters can remove and hold particles 20-25 microns and larger, collecting the least amount of particles and debris of the three filter types. A bed of sand in the filter is what collects the particles and debris. Most sand filters are equipped with a pressure gauge and multiport. The pressure gauge will tell you when the filter is in need of cleaning by measuring the pounds per square inch (PSI).

When indicated, you will perform a backwash procedure to remove particles and debris the filter has collected. The multiport typically has a waste option which becomes useful if your pool has too much water due to large rain loads, or if you need to vacuum undesirable particles or debris directly out of the pool due to certain conditions such as algae.

Since decomposed algae are one micron or less, you can see how if you have an algae bloom, it will virtually be impossible for a sand filter to rectify the situation without a filter aid (there are several different types on the market). Sand in the filter typically lasts five to seven years or until you experience negative filtering problems.

DE Filters

DE filters can remove and hold particles two to four microns and larger, filtering the most amount of particles and debris compared to the other two filter types. A filter grid assembly in the filter coated with diatomaceous earth is what collects the particles and debris.

Most DE filters are equipped with a pressure gauge and multiport, providing the same benefits as described above, but after completing the backwash procedure, you must recharge the grids with another coating of DE. DE grids typically last five to seven years. 

Cartridge Filters

Cartridge filters can remove and hold particles somewhere between what a sand filter and DE filter can accomplish – typically around 15 microns. Cartridge filter elements in the filter are what collect the particles and debris. These filters are not equipped with a multiport, so if you vacuum an algae bloom, a lot of it will collect on cartridges and need to be cleaned off with a filter cleaning product/chemical.

During a typical cleaning you should spray your cartridges off with a garden hose. Make sure your pool builder equips your pool with a way for you to waste water from the pool, should you need to do it. Cartridge elements typically last three to five years. 

Which Pool Filter is Right for Me?

All filters should be cleaned with a filter cleaning product/chemical at least twice a year. For Marylanders, who use their pools for approximately five or six months in the summer, cleanings with a filter cleaning product should be performed mid swim season and at closing time.

Pools that are used year round should consider more cleanings with a filter cleaning product per year. Please note that the backwash procedure is different than using a product/chemical for a filter cleaning. The product/chemical will remove organic and inorganic buildup in the filter that is not removed during the backwash procedure or during a spray off of your cartridges.

Consult your pool professional for help determining which filter suits your needs, lifestyle, and budget best. Your pool professional will also be able to help you determine a properly sized filter for your pool application. 

About this Experts Contributor: Rochele Walton represents Wise Pool and Spa Service, providing pool services in Washington. Since 1992, Wise Pool and Spa has specialized in the installation of new in-ground swimming pools, 3D pool design, hot tub sales and service and much more.

As of September 23, 2015, this service provider was highly rated on Angie's List. Ratings are subject to change based on consumer feedback, so check Angie's List for the most up-to-date reviews. The views expressed by this author do not necessarily reflect those of Angie's List.

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