Filter System Keeps Pool in the Swim

While you’re thinking about the enjoyment you’ll get from a swimming pool, be aware that every pool must have support equipment (pump and filter system) and requires maintenance.

The pump piping is attached to a skimmer box, usually at the side of the pool and partially submerged. The box is equipped with a vacuum fitting and a basket. Floating debris, such as leaves and twigs, are caught in the basket; smaller impurities, such as dirt and oils, are drawn through the skimmer and pump into the filter.

Three types of filter media are commonly used. One of the most popular is the sand filter. In these, water is drawn across layers of sand, which trap impurities. Next are cartridge filters that contain a fibrous fabric that screens impurities. And finally, some filters contain a white, powdery substance known as diatomaceous earth.

If you suspect that water-quality maintenance is a perpetual nuisance, you’re at least partly right. If you start with water that may be high in dissolved minerals and metals, or that is too acidic or basic, and then add airborne and swimmer-borne bacteria, suntan lotion, body oils and virtually any substance that could fall from the sky, you have a mix that can grow algae, damage equipment and make swimmers sick.

Though a broad range of chemical treatments is available, chlorine compounds are the most common.

Even though you don’t have to be a chemist to treat your pool water, some people would rather not bother. These homeowners turn the job over to professionals, who test and treat on a weekly basis.

Another approach is to have the dealer test the first water in the pool--or of the season--treat it for minerals, metals and pH balance, and then set up a purification regimen for you to follow. And finally, you can choose a line of chemicals from any dealer, buy the testing kit that goes with it, do some reading and handle the job yourself.

The National Spa and Pool Institute (2111 Eisenhower Ave., Alexandria, VA 22314) also offers easy-to-follow information on pool care and chemical safety.

The key to effective chemical use is the pH balance of the water. On the pH scale, which ranges between 0 and 14, the ideal balance is 7.4 to 7.6. If the balance is tipped too far toward the alkaline side, the bacteria-killing capacity of the chlorine is reduced, water may appear cloudy and scale will begin to form on pool walls and filtration equipment.

If the water is too acidic, equipment will begin to corrode, chlorine residual (chlorine left after the initial killing shock) will drop and the water will irritate eyes and skin. Manufacturers package products formulated to raise pH (soda ash, sodium carbonate) or lower pH (muriatic acid, sodium bisulfate), but the trick is in knowing when to use one or the other.

How can you know what the pH balance of your water is at any given time?

The usual choice is a chemical reagent test. Take a sample of water in a test tube, add a few drops of reagent, shake it up and compare the color change to a graduated color chart.

Chlorine content can be tested in a similar manner.