Electrolytic Chlorine Generators

The growing use of Electrolytic Chlorine Generators (ECGs) in the public-pool sector is not a fad but a trend–one that has been spurred on by pool operators who have become increasingly aware of the documented benefits of this technology. The efficient and effective use of ECGs has proven not only to provide better water quality, but also to eliminate the dangerous effects of bulk chlorine handling.

Salt has played a major role throughout history for its medicinal properties. Over 2,000 years ago, Greek medicine discovered the topical use of salt for skin lesions and digestive troubles, and the inhaling of salt for respiratory diseases (Science Tribune, 1999). Bathing in a brine solution was increasingly used in the treatment of skin diseases like psoriasis, dermatitis, chronic eczema, as well as for arthritis. While these mixtures are a stronger saline solution than used in pool applications, the theory behind salt utilization in swimming-pool water provides insight into why the process is gaining acceptance.


ECGs, known as Salt Water Systems, were first introduced in the late 1970s for swimming pools and spas when the technology was unknown to the industry. This same process–invented in the 1960s–was widely used for waste-water treatment and industrial applications. Since the late 1990s, there has been a major shift in acceptance. ECGs have gained world-wide approval, and are now recognized as the best methodology for generating a chlorine sanitizer for both private and public pools and spas.

How They Work

Salt is added to the pool or spa to establish a 3,000-parts-per-million (ppm) concentration. This is equal to only 7 percent of the salinity level in sea water, which is 35,000 ppm. The pool user cannot taste the salt at 3,000 ppm, as this level is below the normal taste-threshold, and less than the human body’s salt concentration of 4,000 ppm. One of the best features of this electrolytic process is that the salt continuously recycles itself. Adding salt is infrequent–normally about two or three times a year in outdoor pools and even less in indoor pools. Indoor air quality immediately improves as well when the salt system is utilized. (Pure food-grade salt is added at 50 pounds per 2,000 gallons of pool water to meet the 3,000 ppm standard.)

An electrolytic cell or cells is installed in the recirculation system after the filter and heater. As the filtered water flows through the cell, a small amount of DC current is applied to the cell blades, which under electrolysis, produces hypochlorous acid, hydrochloric acid, sodium hydroxide and hydrogen gas. The electrolytic process reaches break-point chlorination, destroying bacteria and chloramines, which are the source of chlorine odor, red eyes and most of the negative reactions blamed on chlorine. The process repeats itself, based on the chlorine demand in the pool or spa.

Chlorine Demand Factors

There are eight factors that affect chlorine demand:

1. Volume and surface area of the pool

2. Average water temperature

3. Level of cyanuric acid (CYA) maintained. CYA slows the destruction of chlorine by the sun’s ultraviolet

rays in outdoor pools.

4. Bather load. As the number of bathers increase, so does sanitizer demand.

5. Amount of direct sunlight/UV exposure. More sunlight exposure increases the rate at which sanitizer is consumed.

6. Exposure to vegetation and airborne debris. Dense landscaping increases nitrates and phosphates, which are the nutrients that enhance algae growth, thus requiring additional chlorine usage.

7. Chemical dilution due to rainfall, backwashing, etc. Loss of water also creates loss of sanitizer.

8. Main filter runtime and pool circulation patterns. Sanitizer is only introduced when the pump is running. Waterfalls and other water features increase the demand for sanitizer.


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