By Thomas M. Lachocki, Ph.D.

Recreational water treatment is similar in many ways to municipal or point-of-use (POU) drinking water treatment. Because of these similarities, and despite the differences, organizations that provide services and products to the drinking water industry may find opportunities to tailor their products to the recreational water field. The first step to identify opportunities is to understand recreational water treatment. This article summarizes some of the topics relevant to the care of commercial (public) and residential swimming pools and spas. Fortunately, there are more than 1,000 classes for operators or service personnel offered each year that provide in-depth information.

Defining recreational facilities
The recreational water field can be broken into two major segments: residential and commercial. Residential swimming pools and spas, which are more numerous, usually have smaller water volume, are less sophisticated and less regulated. In contrast, commercial pools and spas on average are bigger, have higher bather loads, and fall under the jurisdiction of local health departments. Recreational water venues are regulated by state and local health codes that establish higher standards for commercial facilities and the people who care for these facilities. Since pool operator classes are taught by local instructors, they provide information about local codes. Of course, federal rules covering pesticide registration, “right-to-know,” hazard communication, and hazardous material transportation also apply to the recreational water field.

Commercial or public recreational water facilities include hotels, motels, health clubs, therapy facilities, schools, universities, hospitals, municipal facilities, competition pools, YMCA/YWCA, Boys & Girls Clubs, Jewish Community Centers, and water parks with many unique water environments. As the size of the facility increases, it becomes more common that trained professionals are on site to operate the facility. In other cases, the facility is visited and serviced by a company that has certified personnel. Although this article focuses on commercial venues, many of the concepts also apply to residential applications.

Disinfectants must be suitable for human contact. In addition, disinfectant residuals must be constantly maintained to ensure sanitary conditions and prevent disease outbreaks. The most common disinfectants release chlorine (hypochlorous acid) into the water. In spas, bromine-releasing chemicals (hypobromous acid) are commonly used. Water balance is maintained to protect the facility and circulation system components from damage due to corrosion or scaling. Additional care must be taken in recreational water to minimize irritation to eyes and mucous membranes. The water balance parameters include pH, total alkalinity, calcium hardness, temperature and, to a lesser extent, total dissolved solids (TDS).

New chemical treatment technologies are finding use in recreational water. For example, ozone as a supplemental oxidizer and disinfectant is used in selected pool and spa applications. Ultraviolet light is used in some commercial facilities. In addition, electrolytic cells convert salt (sodium chloride) into chlorine. In these systems, salt is added to the water to establish an approximate 3,000 milligrams per liter (mg/L) level.

Other common traits
Similarities between drinking and recreational water treatment include factors associated with chemistry, microbiology, engineering, facility management and application technology. In either application, the water is ingested, contacts people’s skin, and can emit vapors that can be inhaled.

The physical facilities have some common factors as well. For example, filtration removes contaminants in both applications. The filters used to purify recreational water include high-rate sand, cartridges or grids that are coated with diatomaceous earth. Pumps are used to transport and circulate water. A variety of products help improve water quality and clarity. Automatic chemical feeders maintain disinfectant residuals and pH. An increasing number of facilities use sensors or probe technologies to monitor water quality and control the addition of chemicals to the water. Recently, wireless, web-based monitoring and control technologies have been introduced.

Water in any container—a bucket, bath tub, lake, stream, pool or spa—poses a drowning hazard. Important design criteria including barriers, self-closing and self-latching gates, warning signs, and caregiver education for children prevents tragic loss of life. Particular care must be taken when children are in the vicinity.

General differences
The differences between drinking and recreational water are driven by customers’ needs. Basic business texts commonly review mankind’s hierarchy of needs and show that physiological survival and physical safety take precedence over higher level needs of belonging, esteem and self-actualization. Drinking water satisfies the most basic physiological survival need of mankind—although innovative marketers have positioned certain water products to satisfy higher-level needs with “prestige” products. In contrast, a swimming pool or spa focuses on higher-level needs like belonging with family and friends, esteem, prestige and self-fulfillment. As a result, products and technologies must consider how they help satisfy these specific needs. As the population ages and sedentary lifestyles become more common, recreational water’s role is changing to satisfy basic physiological needs as an environment to maintain or recover physical health and fitness.

Drinking water and recreational water differ in how the water is maintained in a sanitary state. Once drinking water is filtered, disinfected and transported in the distribution system, water quality is largely maintained. Recreational water has a greater challenge to maintain a constant disinfectant concentration because the water is often exposed to outdoor environments and frequently contaminated. In addition to microbial contaminants from washed off skin, saliva and the environment, it’s estimated that 0.1 grams of fecal matter is introduced from each bather.1 Organic and inorganic contaminants from the environment, cosmetics, and flora and fauna further complicate the system.

Most commercial pools use hypochlorite-based chlorine, releasing chemicals like sodium or calcium hypochlorite. Elemental chlorine gas is used in a relatively few facilities, and the number is decreasing. Since many pools and spas are exposed to sunlight, cyanuric acid has been used since the 1960s to extend chlorine’s half-life, which is about one hour in the absence of the cyanuric acid “stabilizer.” In addition, chlorinated isocyanurates, which release chlorine and cyanuric acid, are commonly used to treat recreational water.

There remains a need to find ways to protect people from recreational water diseases. For example, as shown in Figure 1, the Centers for Disease Control and Prevention (CDC) reported that recreational disease outbreaks have been increasing over the last 10 years.2 The biggest increase is due to chlorine-resistant pathogens like Cryptosporidium. Although some research is ongoing in this area,3 the opportunity exists to explore possible solutions from the drinking water industry. The amount of research and number of talented individuals and companies working in the drinking water industry far exceeds those in recreational water.

The physical systems used in recreational and drinking water differ in the potential hazards they pose. Since swimmers can come into direct contact with plumbing lines under vacuum, injury or drowning due to entrapment or hair entanglement is possible in pools and spas. Fortunately, research has identified facility design criteria, and anti-entrapment covers are available that eliminate the entrapment risk.4 Another difference is that pool and spa water is circulated over and over. As a result, contaminants can build up over time.

Many pools and all spas include a heater in the circulation system. It’s important to maintain balanced water to prevent heat exchanger corrosion, calcium carbonate (CaCO3) scale deposits or etching. The high temperature and aeration in spa water reduces the carbonate buffer capacity of water by driving off carbon dioxide. In addition, the high bather-to-water-volume ratio in spas further exacerbates disinfectant loss, often requiring the use of scale inhibitors.

There’s an excellent opportunity for companies that provide services or products to the drinking water field to pursue opportunities in recreational water. This opportunity is based on the many similarities between these fields. The key to exploring recreational water opportunities is understanding how the differences would require services or products to be tailored to satisfy the needs of recreational water facilities or people who use those facilities. This article provides a brief review of some of the similarities and differences between recreational and drinking water. A more in-depth knowledge can be obtained through an operator training class.


  1. Gerba, C.P., “Assessment of Enteric Pathogen Shedding by Bathers During Recreational Activity and its Impact on Water Quality,” Quantitative Microbiology, 2:33-68, 2000.
  2. Lee, S.H., et al., “Surveillance for Waterborne-Disease Outbreaks – United States, 1999-2000,” Mortality and Morbidity Weekly Report, SS-8, Nov. 22, 2002.
  3. NSPF issued a two-year grant to the CDC to research ways to reduce disease outbreaks due to chlorine-resistant pathogens.
  4. Rowley, W.N., “Suction Entrapment & Hair Entanglement/Entrapment,” National Swimming Pool Foundation Safety Compendium, In Press, 2004.

About the author
Dr. Thomas M. Lachocki is the chief executive officer of the National Swimming Pool Foundation® (NSPF®). Before joining the foundation last year, Dr. Lachocki was responsible for product development for a leading recreational water treatment company. He has performed research, presented findings and published papers in diverse fields including recreational water treatment, surfactant science, synthetic lubricants, industrial catalysts, solvents and combustion chemistry. He has been granted six U.S. patents that have been issued and are practiced in at least eight countries. He earned his doctorate in organic chemistry from Louisiana State University and a bachelor’s degree from Lock Haven University. He can be reached at (719) 540-9119, (719) 540-2787 (fax) or email: [email protected]


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