Hayward AquaTrol Salt Water Chlorine Generator for Above Ground Pools. The Aqua Trol is an automatic chlorine generation system with a built-in filter pump timer designed specifically for above ground pools. The operation requires a low concentration of salt (sodium chloride) in the pool water at levels low enough that it normally will not be tasted. The Aqua Trol automatically generators chlorine sanitizer your pool by converting the salt into free chlorine which kills bacteria and algae in the pool. Because chlorine will revert back to sodium chloride after killing the bacteria, these reactions will continuously recycle virtually eliminating the need to add sanitizing chemicals to your pool. The only time you may need to add more salt to the pool is when water is replenished due to backwashing, draining, or splashing (not evaporation). The Aqua Trol incorporates a built in timer to control the pool filter. This timer insures that the proper daily filtration and sanitization occurs. The Aqua Trol is designed to handle the purification needs of the average residential above ground swimming pool of up to 18,000 gallons (67,500 liters). The actual amount of chlorination required to properly sanitize a pool varies depending upon bather load, rainfall, temperature, and the pool's cleanliness.