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The Importance of "Filtering Efficiency"

Water clarity depends on three factors: proper chemicals balances, adequate daily circulation, and quality filtration. Your pool needs a combination of filtration, circulation, and chlorination to stay clear, blue, and ready for swimming.

Most pool owners understand the importance of chemical treatments in pool water maintenance. What is less understood is the vital role the pump and filter play in keeping the pool water looking its best.
Pool water is ciruclated by a small pump. This pump pulls water from the pool through the skimmers, forces it into the filter, then returns the water to the pool, via jets positioned on the pool walls. In our rainy, humid climate, the pool water is constantly exposed to mold and algae spores, dust and dirt, and other airborne or rainborne contaminants. Daily circulation allows these contaminants to be strained out of the water. During the summer months, the pump should be run at least 8 to 10 hours a day.

The filter is designed to trap small particles suspended in the pool water. These particles, called "colloidals," are what makes inadequately filtered water look hazy or milky.
A dirty filter can have a dramatic effect on circulation. As water passes through the filter, millions of tiny colloidals cling to the filtration elements. Eventually, these accumualted particles make it difficult for water to pass through the filter. A dirty filter can reduce pump efficiency by up to 80 percent. In other words, circulating your water for 10 hours a day when the filter is dirty is the equivalent of circulating the water for 2 hours a day when the filter is clean. Many times, a homeowner will find his water is cloudy and greenish, even though the chemical levels are fine, and the pump is running for an adequate amount of time each day. A dirty or damaged filter is the source of the problem.

There is a very easy way to determine whether the filter needs attention: Check the flow of water from the retun jets. If the return flow is strong and steady, the filter is fine. If the return flow is weak and sluggish, it's time to tend to the filter. Filters are equipped with pressure gauges, but these gauges are notoriously innaccurate. As a very general rule of thumb, a rise in pressure of 8 to 10 pounds above normal operating pressure indicates that the filter requires service.

Diatomaceous Earth (DE) filters use a powder called diatomaceous earth to strain out impurities. Diatomaceous Earth is a fine powder, made from the pulverized fossils of aquatic plants. This product is very inexpensive, and readily available at home and garden centers. Each time you backwash a DE filter, you flush both accumulated dirt and debris and spent DE from the filter cannister. FRESH DE MUST BE ADDED AFTER EACH BACKWASHING! Failure to replaenish the cannister with fresh DE can cause severe damage to the internal elements of the filter.

There is a simple formula to figure out how much DE should be added to your filter. First, determine the size of your filter. Filter size is determined by the square feet of filtration area inside the filter cannister. This number is found on a specifications plate on the front of the cannister. (Most filters carry a filtration area of 36, 48, 60, or 72 square feet.) Using a one-pound coffee can, add one can of DE for every 5 square feet of filtration area. It's OK to round off to the nearest multiple of 5; the filter won't mind a tiny bit of extra DE, and after all, this is your swimming pool, not the SATs. A 48 square foot filter requires 10 cans of DE. A 36 square foot filter will function effectively on 7 cans.

Even with regular backwashing, DE filters get grimy with time. It's a good idea to have your filter dismantled and cleaned at least once a year. This affords an opportunity to check internal elements for wear, and to ensure that the filter is working at peak efficiency.

For those of you with cartridge filters, you can improve your filtering efficiency up to 50% by adding 2 coffee cans worth of Diatomaceous Earth to your filter. This is accomplished by adding the DE through the skimmer with the pump on, and stirring it in the skimmer until it is totally dissolved. Each time you hose down the filter cartridges, you'll have to replenish the DE. Even with DE coating the cartridges, it's perfectly safe to hose down the filter elements on your lawn. DE is safe for grass and plants, and as a valuable side benefit, it is an extremely effective snail killer!
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