Feature Article - February 2004
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In the Swim

The Best Strategies for Aquatic Center Peak Performance

By Kim Tobin

Equipment Upkeep: Caring for your Pool's Workhorses

The three basic types of pool filters include Hi-Rate Sand, DE (Diatomaceous Earth) and Cartridge. Routinely, sand and DE filters need to be backwashed to ensure proper filtration and flow rate; cartridge filters need to be cleaned. The following cleaning and maintenance practices should be done at least once annually.

Sand filters, the most common type, usually use a combination of gravel and silica sand. A new filter media, zeolites, which is a mineral rock material, can also be used in sand filters (see sidebar on page 29). Although both types of sand filter media are cleaned and reused by backwashing, it's often necessary to change the filter media over time. Inspect all interior parts—areas under drains and laterals can become cracked even when not fully broken off.

DE filters contain filter grids that can become clogged annually. Although backwashing removes most of the DE and dirt, additional maintenance is often necessary. DE filters should be taken apart a minimum of once a year. The filter grids/elements should first be soaked in a filter cleaner and degreaser to remove body oils and grease and then acid-washed to remove organics.

Cartridge filters have removable cartridges that require routine cleaning. They should be cleaned with a high-pressure hose, then soaked in a filter cleaner degreaser, and then acid washed to remove algae, organics and bacteria.

Zeolites: Everything Old Is New Again...For Sand Filtration

The zeolite, a mineral rock product formed from volcanic ash over millions of years, was first discovered and used by the Romans several thousand years ago in water filtration and building materials. Now suppliers are betting on its success for pool filtration.

Those who sing the praises of these ancient rocks claim that the media can extend filter run time, decrease chloramine problems and even offer potential antimicrobial filtration capability.

The zeolite, which is being marketed primarily for sand filters, offers microporous filtration capability. That structure allows it to capture particles internally as well as on its surface. This increased surface area can be an advantage over sand, which typically filters particles from 20 microns to 40 microns. With more surface area, zeolites have the ability to grab particles down to three microns to five microns, according to manufacturers. This can help provide better water clarity.

Because water is filtering deeper into the bed of the zeolite vs. just the surface filtration that sand offers, filters with zeolites also can run longer without having to backwash a system (flushing once a filter loads up with particles), manufacturers report. Typically, with zeolites, a filter can run about four times longer than with sand. Like sand, it is also a permanent type of media, meaning it doesn't wash out. However, it is recommended that it be changed out every five years.

Filtration capability is also being taken a step further with the application of antimicrobial chemicals to the zeolite's surface . One supplier has introduced patent-pending antimicrobial zeolites, which can inactivate and remove microbes like viruses, bacteria, algae and cryptosporidium.

Another benefit of using zeolites, suppliers say, are their unique ability to absorb and bond with ammonia ions, which can help disrupt the formation of chloramines. Chloramines are generated when a chlorine molecule that attaches itself to a nitrogen- or ammonia-containing compound that can no longer sanitize the water.

Zeolites can reportedly help decrease the odor that chloramines can generate at indoor facilities. To accomplish this, the zeolites load up with ammonia ions. When they reach a certain capacity for holding the ions, that capacity can be refreshed by introducing a saltwater bath to the media. With the bathing process, the ammonia ions are released and sodium ions are captured in their place. The zeolites then become free to capture more ammonia. The frequency of this process will have a direct correlation to the bather load at a facility and the number of organic compounds introduced into the water.

Because of production methods involved in manufacturing zeolites (they are mined, blasted and crushed), they are approximately three times more expensive than sand. However, it's important to weigh the benefits to system efficiency and filtration capability the media provides, according to suppliers.