What Is Commercial Pool Filtration – Introduction

In Blog by Kate Cunha

Filtration is one of the most critical elements of your circulation system in your swimming pool or spa. Proper filtration leads to clean, clear, sanitary water. Improper filtration can lead to cloudy water, along with an unhealthy and potentially dangerous aquatic environment. I’m not here today to fully explore all of the ins and outs of the many forms of filtration out there, nor am I here to tell you which type would be right for you and your pool. That’s a decision for the pool professionals and engineers at your facility and the local inspectors. I am here to talk about the basic methods of filtration available today, along with a few pros and cons of each, in order to help you better understand your own pool.

Sand Filter – For commercial pools, sand filters are the oldest and most commonly used form of filtration. Water filters through a granular media, typically a fine, high grade silica or a combination of coarser sand and gravel. Alternative media, such as crushed glass, can also be an option. Sand filters are cleaned via backwash, the process of reversing water flow through the filter and carrying collected debris to waste. Additional chemical cleaning is necessary from time to time and sand replacement can be necessary every few years. Sand filters, depending on the type, filter out down to a particle size of 25-50 microns. (A human hair is approximately 70 microns; bacteria typically measure around 1 micron.)

Cartridge Filter – Cartridge filters are great for smaller bodies of water, such as spas. Cartridges are cylindrical arrangements of accordion pleated polyester or paper. Benefits of cartridge filters include a smaller footprint, more effective filtration, and ease of cleaning/replacement. Cartridge filters can not be backwashed, due to their construction. Instead, the elements are removed from the filter housing, replaced with clean elements, and then cleaned using a liquid filter cleaner and hose. Their downside is that they should not be installed on high flow/large volume bodies of water. Some could consider the cleaning process a downside. Cartridge filtration is accepted to be in the 10-25 micron range.

DE Filter – The most effective filtration option, DE filters require a large footprint in the pump room, due to being submerged in a water tank, and therefor are not nearly as common as sand filters. DE – Diatomation Earth – are tiny fossilized skeletons of sea plankton that are coated onto a grid of filter elements. Water can either be pushed or pulled through this system. DE is considered carcinogenic and proper handling and storage techniques, including protective gear and breathing protection, must  be observed. DE filters are able to be backwashed for cleaning, but DE is lost in the process and needs to be periodically replaced. A range of 2-6 microns is generally the filtration measurement of a DE filter.

Regenerative Filter – A relative newcomer to the market, regenerative filters utilize DE or a synthetic substitute. In a traditional DE filter, only the channels and depressions of the surface of the filter media trap particulate. The underside of the DE, the side attached to the grid, has a reduced ability to filter. In a regenerative filter, the media is held on multiple tubes, or “fingers”, that are periodically “bumped”, causing the filter media to fall to the bottom of the tank. The filter media is then redistributed, allowing unused sides of the media to be used for filtration as well. Regenerative filters offer a large amount of surface area with a relatively small footprint and are often toted for their water saving qualities, due to the reduced need for backwashing and DE replacement. The water savings may or may not offset the cost of these units, therefore your individual return on investment should be evaluated before purchase.

I have not gone into dept about alternative filter media options, additions, and techniques, of which there are many. Those are best researched on a case by case basis for your facility. The above information is given simply to give you a better understanding of the primary types of filtration currently found in commercial pump rooms. Hopefully, if you’re new to the topic, this will give you a good start.