Swimming Pool Filter Systems For In-Ground Pools And Spas

A swimming pool filter system can be either a pressure or vacuum type of pool filter. The filter media for these various types of swimming pool filters are made of either...

  • Silica Sand.
  • Cartridge Refills.
  • Diatomaceous Earth or DE.

These are the types of pool filter media that are the most commonly used in the swimming pool and spa industry today. A pressure type swimming pool filter is a closed tank that is located or installed downstream from the swimming pool pump used for your circulation and it is inline with the water flow.

The output head pressure of the swimming pool pump is the force that is used to drive the water from your pool through the pool filters that are installed on the system.

As the water is forced through the swimming pool filters, the suspended particles are trapped in the bed of the media of the filters.

Subsequently, as the swimming pool filter media gets packed with the suspended particles from the water being passed through it, the influent pressure (water coming into the filters) increases. As a result of the increased in influent pressure, the effluent pressure (water exiting the filters) is reduced.

Vacuum pool filters on the other hand, are placed before the swimming pool circulation pump. This type of swimming pool filter is normally set up or installed where they are openly exposed to the atmosphere.

The suction side of the swimming pool pump creates the force that will actually pull the untreated water through the filter media. As the media of the filters trap the suspended particles, the vacuum pressure is increased causing a reduction in water flow.

Swimming Pool FilterSand Swimming Pool Filter Installed

Types of Swimming Pool Filters 

There are basically three types of swimming pool filters that are used in the swimming pool and spa industry. they are listed below.  Generally, the purpose of all swimming pool and spa filters as we can see, is to clean debris from the water and help maintain a healthy and inviting pool.

Without a proper swimming pool filtration system installed on your swimming pool, your water will be dirty, and quickly contaminated.

All of which is achieved through your swimming pool or spa filtration process. For the most part, each of the different swimming pool filter systems use a similar process in the the water forced mechanically through the media of the swimming pool and spa filters. The debris in the water is then trapped or filtered out and the water returned back to the pool.

When an engineer decides on a type of swimming pool or spa filter for a particular pool water system, they must take into consideration the space and the budget of you, the client. Some of the swimming pool filters that they normally choose from when constructing a new mechanical system include...

  • Sand filters: This type of swimming pool filter is considered the oldest type used for swimming pool filtration today. It is still the favorite of many in the industry. The filtering efficiency of swimming pool sand filters is 20 - 40 microns which seems to improve even further as the filter continues to get dirty or trap more debris.

Sand swimming pool filters are deem permanent pool filters because their media last for a very long time. This time period could be anywhere from 5 to 15 years before the silica sand has to be replaced in the filter.

The principle operation of all swimming pool sand filters are basically the same.

Water is forced from the top to the bottom of the pool filters.

The sand swimming pool filter media traps the suspended water particles as the water passes through the sand media.

As suspended water particles attached themselves to the edge of the fine silica sand, they cause the gap between each of the sand grain to become smaller and smaller. As a result of this, the smaller particles such as body waste, lotions, hair, and dirt are trapped in the sand media.

This process creates a fibrous maze that eventually filter out the smallest particles in the water coming from your swimming pool. Unfortunately this process also has some down falls. This causes a pressure build up in the swimming pool filters and a reduction in your water flow.

This is an indication that your pool filters have to be cleaned to improve water flow. The cleaning of the swimming pool sand filter is achieve through a process known as backwashing. Overall, sand filters are most economical and easy to maintain; however, they are least efficient.


  • Cartridge filters: These type of swimming pool filters are considered replacement type filters simply because of the type of media that they carry. they are of a pleated designed construction that is wrapped around a harden plastic core. Both ends of the swimming pool filter are sealed to keep the ends in place. A cartridge swimming pool filter is normally operated in the pressure mode; however, there are some cases where they have been installed or used as vacuum swimming pool filters as well. Designed engineers normally choose these types of swimming pool water filters because they do not require a lot of space for installation.
  • They are also environmentally friendly and they require very little water to clean. The only downfall is that these type of filters have to be disassemble for it to be cleaned. The filtering efficiency of a cartridge pool filter is 10 - 15 microns; thus, making these types of swimming pool filters better that that of sand swimming pool filters.

  • Automatic pool cleaners These cleaners act as another form of swimming pool filter as well. Many of these pool robots have a filtering efficiency of 2 microns which is about the same as a DE type pool filter. This means as your swimming pool is being cleaned, the water is also being properly filtered.

  • Diatomaceous Earth Filter: Diatomaceous earth or DE Filters as they are famously called, are in away very similar to swimming pool sand filters. the difference is the type of filtering media used in each, where silica sand is used in the sand filter, DE is used in this type of swimming pool filter. There are two know types of DE filters used today. One is called vertical grid filters and and the other called regenerative filters. When it comes to filtering efficiency, DE swimming pool filters are the best. They can filter down to 2 - 3 microns which can guarantee the your swimming pool water will be properly filtered. If you desire super clarity of your swimming pool or spa, then a DE filter would be a better choice.
  • Diatomaceous earth filters are considered the most efficient swimming pool filter because they catch the smallest particles; thus, providing you with the cleanest pool water possible. However, there is a downside to this type of filtering unit, they are both expensive to buy and maintain.

    The filtration of your swimming pool water is extremely important because of serious water contamination which can cause illness. If you don't have a good swimming pool or spa filtration system installed, you asking for trouble. Keeping your family or guest healthy during the use of your swimming pool or spa, not only depends on your pool disinfecting or sanitation! It also depends heavily on a properly installed swimming pool filter.

    swimming pool filter has to have the right filter media for the job that it has to do!

    Swimming pool care home page

    Back To Top

    New! Comments

    Have your say about what you just read! Leave me a comment in the box below.

    Pool Filtration