Your filtration system plays a huge role in keeping your pool clean and ready to use. But not all filters work the same, and some are likely not the right fit for your setup. We’re here to filter out the noise and help you make the right decision.
3 Types of Pool Filters and Benefits
Sand filters are one of the oldest and most tried-and-true methods of pool filtration. The filter’s No. 20-size sand granules are finer and sharper than beach or playground sand. The finely ground sand catches dirt and debris particles as small as 25 microns, as the pool pump pushes water through the sand filter system, sending clean water back into the pool.
The lower the micron level, the better filtration properties a filter has. While sand filters are perfectly safe and commonly used, sand has a higher micron level than other filters and doesn’t clean smaller particles. Additionally, sand filters usually need to be backwashed about once or twice a week — when the filter’s water pressure reaches 10 psi above the initial pressure reading — to remove accumulated dirt and debris from the filter. It’s also best to chemically degrease the filter twice a year to get the most out of its lifespan.
Sand is such a common option for filter media because it’s ubiquitous, long-lasting, and cheap to replace. Sand filter tanks are typically made of fiberglass and can last up to 10 years or more. The sand that does the dirty work inside of the filter should be changed every three to four years to maintain effectiveness. The bulk of the cost of a sand change is in the labor to remove and replace the sand.
Diatomaceous Earth (DE) is another option that looks something like powdered sugar, but is actually crushed fossil material, diatoms, made of silica. It’s a great abrasive cleaner and pool filtration medium. A DE filter works in the same way that a sand filter does, except it includes a mesh grid coated with DE instead of lump sand.
DE has some of the best filtration properties because it catches particles as small as 4 microns — six times smaller than a sand filter’s porousness. This is actually fine enough to filter out a single human blood cell! But DE filters usually have a shorter lifespan, and the backwashing process is more labor-intensive and potentially dangerous if performed improperly.
DE also requires more care to protect operators when handling since it’s a carcinogen and causes respiratory problems when inhaled. DE poses no risks to bathers as the material is maintained inside of the filter and can’t create dust when wet. Many local and state laws also prohibit dumping DE improperly, throwing in another complication. Backwashing procedures need to incorporate a process to contain and dispose of the spent DE. Sometimes the filter can get clogged and the entire DE filter needs to be disassembled to remove accumulated material. DE grids are made of a fine fabric and they are very fragile. If the grid tears, the filter cannot capture any debris and dirty water circulates back to the pool. This is not a healthy condition for swimmers so it’s important that your pool operator understands the ins and outs of DE filters and processes.
A more recent popular option for commercial pool filtration is a cartridge filter. Unlike organic media, the cartridge filter is made out of a polyester grid, which has a lower micron level than a sand filter, but slightly higher than a DE filter.
You generally pay a higher price upfront for a cartridge filter system, but you’re also paying for convenience in operation. There is no backwashing needed for cartridge filters so they often can be used where other systems cannot because they don’t need any connection to a sanitary sewer. Cartridge filters do need to be cleaned manually, however, and the process can take some time. Fortunately, if the system is designed properly with sufficient capacity, manual cleaning only needs to be done once a month or so.
It’s a good idea to have a backup set of cartridges to swap in while you clean the others so that the pool can keep filtering while you work. After cartridges are cleaned they should be allowed to dry and “fluff” back up to maximize their effectiveness. A cartridge filter tank can last 10 years or more, but the cartridges inside should be replaced about every 2-3 years.
Which Pool Filter is Best for My Pool?
The answer really depends on the size of your pool, and how your facility handles its wastewater.
Sand filters are excellent options for commercial pools because they don’t need as much maintenance and can be sized up or down depending on the size and quantity of your water tanks. They filter much more water faster than cartridges, and save energy costs proportional to your pool’s size as a result.
We don’t typically recommend using a DE filter with commercial operations because the cleanup is too frequent and time-intensive to justify their use on a large scale. Because DE is a potential carcinogen and hazardous when inhaled, increased safety protocols for these cleanings can be cumbersome and wasteful. However, with proper care and safe diligence, DE filters are a perfectly fine option for your private pool at home.
Despite the lack of cost efficiency, you may opt for cartridge filters if your pool gets less use, is smaller, or you would prefer to spend less time maintaining it. You may also want a cartridge filter if you don’t have your pool’s wastewater connected to your sewage line, or if you live in a state or area that prohibits discharging chlorinated wastewater into your sewage line. You could install a dechlorination system before it reaches the sewage line, but this is more cumbersome than purchasing new cartridge filters every few years.
Just as important as the filter type is the system design, so that it can effectively handle the demands of your facility considering its size and usage. Systems need to be able to handle the busiest and hottest days and still maintain water clarity. Of course, all commercial filter systems need to meet or exceed requirements of the local health authority.
There are many more technologies and filtration media on the rise that we haven’t covered, but that doesn’t mean they’re not as effective as the “Big Three.” Glass filtration systems are relatively new and more expensive, but offer lower micron filtration levels and last longer than their traditional sand counterparts. Cellulose fiber is most similar to DE and safer to handle, but also much more expensive.
So, which filter is right for your commercial pool? If you’re still having trouble answering that question yourself, we’d love to help you find your solution!