Cool clean water: a guide to nonchlorine pool water treatments.

By far the most common pool treatments use some type of chlorine. Few alternatives are as inexpensive, or as effective by themselves at both killing bacteria and breaking down organic contaminants, such as algae, soap, suntan lotion, skin cells, spit, sweat, and urine, that accumulate in pools and spas. But even though the Environmental Protection Agency has approved chlorine compounds for swimming pool use, some custom home owners question the health risks of chlorine and are demanding nonchlorine treatments.

John Gedney III of E.L. Wagner Custom Pools, an award-winning pool builder in Bridgeport, Conn., says he simply can't afford to have a pool owner potentially mishandle chlorine, which could lead to a buildup of chloramines, a by-product of chlorinated pool treatments that can cause slimy skin, dry skin, skin rashes, and a potent chemical smell (see "Chlorine Chemistry 101," page 00). Instead, he relies on ozone, used in conjunction with a mild bromine sanitizer.

Ozone is just one example of an increasing number of nonchlorine pool treatments that are finding expanded markets in the United States. Many of these products have been developed in Europe, where they have a significant track record. All of them are more expensive than the average chlorine treatment, and (like chlorinated treatments) all require a periodic shock--an extra-high dose of a chemical treatment (applied when no swimmers are in the water) to control aggressive algae, slime, and water molds. Here's a rundown of the nonchlorine products.

Bromine

Bromine is more unstable than chlorine in sunlight (as much as 75 percent of the free bromine' in a pool can be depleted by the sun in just two hours), so it is not by itself a viable alternative to chlorine. However, in conjunction with an effective oxidizer (a treatment that will break down the accumulation of dead organic matter), it can be used in very light doses to disinfect. Bromine is much more effective than chlorine in hot water, so it is a common treatment for spas and hot tubs. Formulations typically have a low pH of 4.0 to 4.5, creating an acidic solution. Depending on the amount of bromine used, the pH of the water may have to be adjusted with soda ash, a relatively benign additive compared with those used to balance the pH in a chlorinated system.

Biguanide With Hydrogen Peroxide