basics pool filters

Within any new swimming pool or hot tub, one of the most important considerations you’ll be making as a buyer is the filter. There are several different kinds of pool filters available, with different primary functions and benefits, and having the right one in your pool will keep you and your family safe from contaminants at all times.

At Dolphin Pools & Spas, we can help if you’re unsure about anything related to your pool’s filter. Our pool design experts will go over the right kinds of filters for you based on your pool type and needs, plus give you tips on how to change and maintain filters in the future. In part one of this two-part blog, we’ll go over some of the basic functions of a pool filter, what it helps eliminate, and what’s meant by the term “effective filtration area.”

Pool Filter Basics and Functions

The pool has several mechanical components involved in it, and the filter is one of the most vital. After the pool pump pulls water through the skimmer and pushes it into the filter, the filter stops debris, dirt and other contaminants from passing through as water is released back out into the pool.

These contaminants are instead held in the filter rather than making their way into the pool. In most standard pools, a full cycle that filters all the water in the pool takes about eight hours – though this can vary significantly based on your filter type and the size of your pool.


The term “micron” describes one-millionth of a meter, and it’s used regularly within pool filters and other forms of filters in several home areas. Different filters come with different filtering capabilities – some can trap all particles below 10 microns, for instance, while others can only trap those under 50 microns.

For a basic reference point, here are the general sizes in microns of certain items:

  • Thin ink pen nibs: 150 microns

  • Human hair: 50 to 100 microns

  • Pollen: 30 microns

  • Bacteria: 2 microns

Not all filters come with the same filtering qualities here. Some fill filter ultra-fine particles with low micron counts while others are only meant to filter hair or larger items.

Effective Filtration Area

So what kind of filtration is your pool getting? Well, a lot of the answer here comes down to what’s known as the “effective filtration area.” Contrary to some myths, this term does not refer to the amount of water that’s filtered or the total pool space – rather, it refers to the surface area of the filter media itself.

When we say “filter media,” we aren’t referring to the tank. No, we’re talking specifically about the filtration piece itself, which will define the area filtered in your pool. Filtration areas range all the way from two square feet up to 600 square feet depending on the kind of filter you use.

In part two of this blog series, we’ll go over the common types of pool filters available, plus how you go about choosing the right one and using it properly. For more on this, or to learn about any of our custom pool construction services, speak to the pros at Dolphin Pools & Spas today.