Wikipedia Prevention of diseases in swimming pools and spas
Disease prevention should be a part of every water quality management program for pool operators, just like the prevention of drowning, injuries, and sunburn.People are less likely to be exposed to polluted water at swimming pools and spas that are monitored regularly and audited for health hazards. The pool water has to be continuously disinfected by desinfectants so that the concentrations set by standards are maintained throughout the pool water, and also the pH, the clarity and the total alkalinity of the water has to be maintained in accordance with the requirements set by standards.Don't swim in locations where the pool water is not continuously disinfected, or do not use or have a defective filtration system.
The education of parents of small children and other recreationists with regard to good hygienic behavior at swimming pools is also important for improving health safety at swimming pools and spas. People should also be cautioned about swimming in pools if they are suffering from gastroenteritis or other illnesses where viral pathogens might be transmitted from swimmer to swimmer via pool water.
Since most swimmers are exposed to pathogens by swallowing the water, people will be less likely to get sick if they swim without submerging their head