The Different Types of Pool Filters and How They Work

Nothing is more refreshing on a hot summer day than taking a dip in a pool. That’s one of the reasons swimming is one of the most popular forms of exercise and recreation.

It’s also why it’s a booming industry in both construction and maintenance. But one key component is often overlooked. It also happens to be one of the most important when it comes to maintaining a healthy and safe pool: the pool filter.

In this guide, we take a look at all the different pool filters available and how they work so you can choose the best one for your pool.

How a Pool Works

There are 10.4 million private and 309,000 public pools in the United States. California leads the way with more than 1.5 million residential pools and 40,000 public pools. Florida is a close second with close to 1.3 million private pools and almost 25,000 community pools.

That’s a lot of pool supplies! But many people don’t think twice about the components that go into making their pool work. They take the contractor’s suggestions or a pool company’s word for it when getting a pool installed.

These people often push you toward the most expensive option, which doesn’t always mean the best system for your needs. Knowing what all the parts are, how they work, and their benefits help make you a smarter pool owner.


In general, there are three main components to a pool filter system:

  • Pump
  • Filter
  • Chlorinator

A pool heater is an optional component, that fits between the filter and chlorinator in the process.

These components each have a particular job to do in the five-step process. A pool filter pump sucks the water through a skimmer and drain to remove large debris. The water flows through a swimming pool filter where smaller debris gets caught.

Next, filtered water passes through a heater or goes directly to the chemical stage. Once the water is in the chlorinator, chemicals get added to make the water safe for swimming (and the occasional consumption). After it goes through the chemical process, the water gets returned back into the pool.

Before understanding the different types of filters, it’s important to know how they’re measured. Microns get used to measure the size of filter openings, thus determining their effectiveness. A micron is one-millionth of a meter.

For example, a 5-micron filter will catch smaller particles than a 20-micron filter.

Traditional Pool Filters

The same way filtered drinking water improves your life, the proper pool filter can improve your swimming experience. Each filter works in a different way to give you your desired results.

There are three types of traditional pool filters. These are the most common swimming pool filters, found in a majority of pool filtration systems.


Pool sand filters use #20 silica sand as the filtration agent. As water enters, the pump pushes it down through sand beds inside the filtering tank.

Debris and particles get trapped by salt’s sharp edges. The clean water then flows through the bottom back into the pool.

As this process repeats itself, dirt and debris gets trapped in the filter. When the filter gets full, the water flows slower.

This calls for frequent “backwashing” where water enters through the bottom and flows out of the top. The collected debris washes away and the water gets removed by a separate line.

This process needs to get repeated once a month (give or take) to keep the filter clean and working efficiently. When the sand loses its edge and filtered water gets put back in the pool dirty, it needs to get replaced.

The sand itself is cost-efficient and easy to buy but there are disadvantages to a sand filter. A lot of water gets lost during backwashing and it needs to get replaced.

The filter is also not as efficient at removing smaller debris as other filters. This is because sand only removes particles that are 20-25 microns. Particles smaller than this aren’t caught and re-enter the pool.


A cartridge filter is a step up from a sand filter but still isn’t the most effective at removing impurities. A cartridge filter is in the shape of a cylinder and usually made out of polyester.

When water passes through, debris 5-10 microns in size get trapped in the cylinder. The cylinders hold the dirt and debris until they’re cleaned. This is a simple and easy process.

You clean the cylinders with a hose, cleaning tool, or soak them in soap until they’re clean. Once they’re clean, you put them back in the system. Because of their low maintenance, cartridge filters are very popular, despite costing more than sand.

When choosing a cartridge filter, there are many style options with many sub-styles:


  • Threaded
  • Non-threaded
  • Slots
  • Collar
  • Stepped edge
  • Twist-lock


  • Flat
  • Stand-off
  • Threaded
  • Stepped edge
  • String loop


  • Threaded
  • Non-threaded


  • Arched
  • Bar
  • Knob
  • S-handle

Because of the many types and sizes, cartridge filters are

Diatomaceous Earth

Of all the traditional pool filters, a diatomaceous earth filter is the most expensive and effective. Diatomaceous earth is aquatic organisms that fossilized called diatoms.

The diatomaceous earth coats the grids inside the filtering tank. When water passes through, the diatomaceous earth filters impurities as small as 2-6 microns.

A diatomaceous earth filter gets cleaned like a sand filter. In other words, it uses the same backwashing system. You add diatomaceous earth to your filter system as needed.

Some pool owners add diatomaceous earth to their sand filters as well for added efficiency. One major drawback to diatomaceous earth is that it’s a carcinogen. This means you must wear safe-handling gear including gloves and breathing protection.

Another drawback is this system doesn’t get rid of chloramines, which causes a strong chlorine odor. Think of the way an indoor pool smells. If you’re using a diatomaceous earth filter, you should add a UV system to get rid of them.

Modern Aftermarket Filters

There are many modern filtration systems available, so you’re not pigeon-holed into one of the traditional three. Many people are finding the benefits of using crushed glass and zeolite, which we explain below.

Crushed Glass

Crushed glass is good for the environment as it’s made from recycled glass. The glass gets crushed to the size of #20 sand, giving it the same filtering process.

Whereas sand lasts five years max, crushed glass’s lifespan is 10 years. The glass gets activated, giving it a negative charge that attracts micro-particles.

If you use crushed glass, more of the filter media gets used reducing the backwash time which saves water.


Zeolite is getting used more by pool owners and maintenance techs, but it’s not exactly common. It’s an all-natural mineral that forms in volcanic and sedimentary rock. They’re crystalline structures that trap molecules inside.

They’re resistant to high temperatures and pressure which is why it’s used in many commercial industries.

Zeolite has half the density of #20 sand. This means that if your filter tank calls for 50 pounds of sand, you only need 25 pounds of zeolite. The cost is higher than sand, but they work at a higher efficiency.

Like diatomaceous earth, zeolite filters impurities 2-6 microns in size.

Regenerative Filters

Regenerative filters are new but rare in the swimming pool industry. This filter media is like diatomaceous earth but synthetic substitutes get used in most cases.

This makes them filter with the same efficiency as diatomaceous earth filters, without the dangers of handling it. These filters take up a large amount of space which reduces backwashing and replacing diatomaceous earth or the synthetic substitute.

This saves a lot of water but on a smaller scale, this won’t offset much. That’s why these filters work best in a commercial setting. Due to their high cost, they’re not cost-effective for private pool use, although they are available.

What to Choose:

Here’s a look at all the filters using cost and effectiveness:

Clear Water / Least Expensive – Sand filters, crushed glass

Clearer Water / More Expensive – Cartridge filters, zeolite

Clearest Water / Most Expensive – Diatomaceous earth, regenerative filters

Keep in mind, the amount of use the filter gets plays a part in its effectiveness and how often it needs maintenance or to get replaced.

Spa Vs. Pool

Although spas are not swimming pools, they do use the same filter system. Cartridge filters are the most common for hot tubs.

Because spas, in general, get used less than pools, filter maintenance gets forgotten more. Remembering these tips will reduce your water impurities and keep your spa flowing smooth:

The water in your spa reaches higher temperatures, which breeds bacteria. Keeping your spa filter in tip-top shape helps your water and your family stay healthy.

Get the Best Water Quality at the Best Prices

Having the right pool filter means you and your family can enjoy your pool safer and longer. Don’t make the same mistake millions of other pool owners make and buy an expensive filter.

There are effective, longlasting, and efficient pool filters available. You only need to know where to look. That’s where DiscountFilters.com comes in.

We sell quality filters for 40%-70% less than major retailers. Our products are all made in the U.S.A. and come with a one-year full-refund guarantee.

Check out our blog or contact us today if you have any questions.

2 thoughts on “The Different Types of Pool Filters and How They Work”

  1. Trying to understand water filtration system. Our well water is aprox 75 feet from our septic tank drain field. We didn’t know this when we moved in. Now we are looking/understanding our options.

  2. I completely enjoyed your article on understanding filters. It was very informative and explained in layman’s terms. Thank you!
    Robert Bryan in Rapid city. S.D.

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