How To Buy A Pool Filter

To ensure that your pool remains clean and sparkling, it’s essential to choose the right pool filter system. There are several factors that come into play when selecting a pool filter, and all the information can get confusing.

In this article, we’re going to take a look at how pool filters work, what you need to consider when choosing one and how to maintain a pool filter for maximum consistent performance.

Here’s our guide on how to buy a pool filter.

How Pool Filters Work

Pool filter system

Pool filters are magical contraptions that remove unwanted substances in your pools. They might come across as complicated, but they’re quite basic and straightforward in how they work.

Normally, a pool pump generates pressure to circulate pool water through a filter which sanitizes the water and returns it to the pool cleaner and safer.

But what you really need to know is there are three basic types of pool filters and they use different methods to keep your pool water transparent and safe. In this section, let’s discuss how each one of them works.

1- Sand Pool Filters

As you can guess, sand pool filters extract dirt and other particles from your pool water by the use of specific types of sand media. Traditionally, a sand pool filter is composed of an oval tank filled halfway through with sand, a water pump, a valve switch, and pipes connecting the entire device from the pool to the machine. 

The valve switch could either be placed on top or on the side of the tank which tells you the current mode of your machine. Sand pool filters basically work this way: the water pump draws water from your pool to the top of your tank. It passes through the sand which can filter down to 20 microns. Then lateral plastic pipes siphon out the clean water from the bottom of the sand bed to put it back to your pool. 

There are other functions of a sand pool filter like recirculation, backwash, rinse, waste, and winter functions. While the filter function is the most important part of it, the other functions are also necessary to keep your sand pool filter in the best condition possible.

2- Cartridge Pool Filters

Cartridge pool filters meanwhile use a different way to remove unwanted particles from your pool. Instead of needing heavy amounts of silica sand, this uses either one or four replaceable cartridge filters made out of spun, bonded polyester that can trap small particles of down to 10 microns.

It’s also smaller compared to a sand pool filter since the machine doesn’t need to be filled up with sand making it a lot slimmer. It works by directing water into the cartridge filters. The water is then cleaned out as it passes through each sheet. Next another pipe which is usually below the tank is pumped back to the pool.

3- Diatomaceous Earth (DE) Filters

Diatomaceous Earth Filters work almost the same way as cartridge filters but better. They can catch dirt as small as just 2 microns, although most D.E. filters typically remove particles down to 5 microns.

Instead of using polyester cartridges, this filter uses diatomaceous earth powder or crushed fossilized exoskeletons of tiny diatoms which is a type of algae. The DE powder is coated in the grids of the filter housing to catch unwanted particles. Unlike cartridge filters though, you also need to do a bit of backwashing to remove the layer of dirt that builds up on your grid.

While D.E. is highly effective, it poses some health hazards to people with certain conditions. Also, there is some fear that D.E. is a carcinogen but this hasn’t been scientifically proven.

The infographic below shows the pros and cons of these three types of pool filters.

Pros and cons of pool filter types

Above Ground vs. In-Ground Filters

So now that you are aware of the types of pool filters, the kind of pool filter you need must also depend on the kind of pool you have. Hence, pool filters have 2 kinds: above ground and in ground.

Above ground pool filters are usually smaller and they typically can only be used for up to 15,000 gallons of pool water. In ground pool filters on the other hand, require a little bit of digging and more plumbing for it to work. Some pool filters are quite versatile and can be used for both above and in-ground pools.

Other Considerations When Buying A Pool Filter

Pool Size

The bigger your pool is the larger your filter must be. This is the reason why quad-cartridge filters are available. A regular sand pool filter might not be enough to clean olympic size pools (unless you have the time for tons of backwashing). By finding the right filter for the size of your pool, you can guarantee a much safer pool water quality. Plus, you can also ensure that your machine will last for a longer period of time.

Filter Quality

We’ve already discussed the filter quality of each machine so the type you choose depends on your needs. Sand pool filters don’t have the capacity or performance to deal with tons of dirt and substances. So, if you own a public pool or you’re planning to host frequent pool parties, then it’s best if you invest in a cartridge or DE filter. But if the pool is for personal use or family use only, then a sand filter may be adequate. Most in-ground pool owners opt for cartridge or D.E. filters as these generally are capable of filtering out smaller particles.

Ease of Maintenance and Replacement

If you can’t lug around over 30 pounds of sand to replace your filter media, then it’s best to use other pool filters. Cartridge pool filters are known to be the easiest ones to clean and maintain, while D.E. filters take up the most time for maintenance (more on this below).

Flow Rate & Turnover Capability

All pool filters have different flow requirements. Flow rate has something to do with the filter’s compatibility with your pool pump. If the flow rate of your pump is higher than what your pool filter can handle, the filter will get worn down easily or even damaged. Technically speaking, the flow rate can be measured either by Gallons per minute or Gallons per hour.

Meanwhile, the turnover capability is the amount of time your pool pump and filter take to clean your entire pool water. Most often than not, pool filters can finish cleaning a pool in around 12 hours max. But a lot of products can now do this in just 8 hours or less.

Water Conservation

This is an important consideration especially if you don’t have an unlimited supply of water at home or you can’t really drain wastewater onto the street gutter in your neighborhood. If that’s the case, then sand pool filters and DE filters may not be best for you.


This is definitely a top consideration since you can’t really buy something you cannot afford. Aside from upfront costs, you must also consider replacement filter price and possible installation costs once you choose your device.

How To Maintain A Pool Filter

Man using pool filter


Backwashing refers to the process of cleaning the pool filter through reversing the flow of water. It’s basically pushing out the dirt and other buildup that are stuck in your filter.

You’ll know when it’s time to backwash your sand filter when the gauge shows a pressure rise of up to 10 pounds. However, this process also involves draining away pool water to remove the contaminants in your filter. 

On the other hand, DE filters need backwashing once every month. Just remember to apply a few more DE powder to your grid to ensure proper filtration.

Cartridge Cleaning

While you don’t need to backwash cartridge filters, this doesn’t mean cartridge filters don’t require maintenance. However, maintaining a cartridge filter is easier as you just need to pull out the cartridge from your tank and hose it down. You will also need use special disinfectants for your cartridge to keep it clean and prolong its longevity. Doing so would allow your cartridge to last for up to 5 years.

Filter Replacement

The filter life of your pool filter is another important consideration as it’ll dictate the amount of maintenance and ongoing cost your filter will demand. Sand filters don’t require sand replacement for several years, sometimes up to 7 years. However, when a sand filter has issues, it can result in broken laterals which means sand going into your pool. A broken cartridge or D.E. grid can also cause issues since these can no longer filter unwanted substances in your pool. While cartridge filters will require periodic replacements, a D.E. grid can last up to 10 years.

The Bottom Line

All things said and done, buying a pool filter for your pool isn’t that complicated once you factor in the above considerations and consider your specific requirements.

In our detailed article on the best pool filters, we’ve covered the top pool filters available on the market. You can also check our guide answering the question do I need a pool pump.

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