By John Antretter
Although it has been on the market for 30 years, cartridge filtration is a virtual newcomer to the pool and spa market compared to other filtration options. Cartridge filtration is growing across the industry in pool applications, capturing virtually all of the spa and above-ground pool market. The reason for this popularity lies in the advantages of filter cartridges, which are effective, efficient, environmentally advantageous and relatively easy to maintain.
Pool and spa builders and service technicians must learn to balance the costs needed to achieve unnecessary expectations with energy consumption and the expenses associated with increased service. With a better understanding of the advantages cartridge filtration can provide, pool and spa professionals can make an informed decision.
A brief history of filtration
A properly maintained filter will reduce the pressure in a pool or spa’s filtration system, keep water flowing smoothly and reduce the wear and tear on all equipment in the system. There are three different types of pool filtration: sand, diatomaceous earth (DE), and cartridge.
Many older pools have a sand filter, the oldest method of pool filtration. Tried and true, sand filters do a fine job cleaning particles approximately 40 to 60 microns in size, but require costly backwashing to clean the filter. Backwashing for even a few minutes to remove old dirt and debris may result in the use of as much as 1,135 to 1,892 L (300 to 500 gal) of water. Pool professionals overlook the true cost of backwashing. The water being pumped down the drain has been chemically balanced and heated.
While DE filtration is an improvement performance-wise on traditional sand methods, it still requires the same backwashing as sand filtration. In addition, many local governments no longer allow the discharge of water containing DE into their municipal sewage systems. Also, even after backwashing, DE grids often need to be unbolted from their filter housing and scrubbed to ensure proper cleaning. This high level of maintenance and the waste associated with backwashing, has prompted many in the industry to turn to the third alternative: cartridge filtration. Over the past decade, cartridge filtration has become increasingly popular in new pool installations and as replacements for aging sand and DE filters.
In comparison, cartridge filtration is easy to maintain and cost effective. They do not require backwashing; the homeowner, rather than a service technician, can typically handle maintenance. They are also easily replaced, with the old filters being thrown in the trash and swapped out with new ones in the housing.
Effective and efficient
A new filter cartridge will capture 100 per cent of all particles larger than 30 microns (one micron equals 1/25,000th of an inch); particles smaller than 40 to 50 microns are not visible to the naked eye. Like sand and DE filtration, as a filter cartridge is in use, the filtration fabric will actually start to ‘load’ with particles, making the filter more efficient. After loading, the cartridge will naturally capture a higher percentage of smaller particles even as small as five microns. As any filter captures (loads) particles, the path for other material to move through the filter gets smaller and more complex, making any filter more efficient in trapping more matter of a smaller size.
Larger particles will be trapped on the surface of the filtration fabric; these can be washed off simply with a quick run of the hose. Smaller particles will actually penetrate the media and cannot be washed off. Over time, filter cartridge efficiency will be reduced, as it becomes loaded with these small, invisible particles. For pool applications, if the bathing season is less than six months, a filter cartridge will generally last for two years; if the pool season is longer than six months, the cartridge will last approximately one year.
In spa applications, hot water will remove oils and other contaminants from bathers more rapidly than cooler pool water. Therefore, filter cartridges are more apt to become clogged and need to be replaced. Where homeowners use their spas regularly, replacing filter cartridges every three to six months is recommended. Using a filter cartridge beyond its recommended life can increase the wear and tear on other more expensive components (e.g. pumps) because of the extra force needed to move water through the filtration system.
Some use inferior filtration fabric, which can clog quickly and fail to achieve proper water cleanliness.
