The World Health Organization
The World Health Organization has published international guidelines for the safety of swimming pools and similar recreational-water environments, including standards for minimizing microbial and chemical hazards. The U.S. Centers for Disease Control and Prevention also provides information on pool sanitation and water related illnesses for health professionals and the public. The National Swimming Pool Foundation provides a Certified Pool/Spa Operator certification which is accepted by many state and local health departments.
Pathogenic contaminants are of greatest concern in swimming pools as they have been associated with numerous recreational water illnesses (RWIs). Public health pathogens can be present in swimming pools as viruses, bacteria, protozoa and fungi. Diarrhea is the most commonly reported illness associated with pathogenic contaminants, while other diseases associated with untreated pools are Cryptosporidiosis and Giardiasis. Other illnesses commonly occurring in poorly maintained swimming pools include otitis externa, commonly called swimmers ear, skin rashes and respiratory infections.
Modern digital equipment when used in conjunction with automatic chemical feeders results in stable pH and chlorine levels. Check with your local jurisdiction if you are adding chemicals by hand to the water, since there is generally a wait time within the health code so that swimmers are not injured.
Chemical parameters include disinfectant levels according to regulated pesticide label directions. pH should be kept between 7.2-7.8. Human tears have a pH of 7.4, making this an ideal point to set your pool.  More often than not, it is improper pH and not the sanitizer that is responsible for irritating swimmers’ skin and eyes. Total alkalinity of 80-120 ppm and calcium hardness between 200 – 400 ppm Good hygienic behaviors at swimming pools is also important for reducing health risk factors at swimming pools and spas. Showering before swimming can reduce introduction of contaminants, and showering again after swimming will help to remove any. Those with diarrhea or other gastroenteritis illnesses should not swim within 2 weeks of an outbreak, especially children. Cryptosporidium is chlorine resistant. To minimize exposure to pathogens, swimmers should avoid getting water into their mouths and never swallow pool or spa water.
Maintaining an effective concentration of disinfectant is critically important in assuring the safety and health of swimming pool and spa users. When any of these pool chemicals are used, it is very important to keep the pH of the pool in the range 7.2 to 7.8-according to the Langelier Saturation Index, or 7.8 to 8.2- according to the Hamilton Index; higher pH drastically reduces the sanitizing power of the chlorine due to reduced oxidation-reduction potential (ORP), while lower pH causes bather discomfort, especially to the eyes. However, according to the Hamilton Index, a higher pH can reduce unnecessary chlorine consumption while still remaining effective at preventing algae and bacteria growth.
To help ensure the health of bathers and protect pool equipment, it is essential to perform routine monitoring of water quality factors (or “parameters”) on a regular basis. This process becomes the essence of an optimum water quality management program.