Introduction Hot water bacteria: the simple facts What is hot water bacteria? Hot water bacteria, Legionella pneumphila, are bacillus shaped and non-spore forming, and survive and grow at water temperatures ranging from 20°C to 45°C; bacteria growth is enhanced by low concentrations of iron, zinc and potassium in water, and stagnant or low flow water areas encourage it. In its most virulent form it can cause Legionnaire’s disease - its discovery occurred in 1976, when attendees of the American Legion Convention in Philadelphia in the USA contracted the disease. However, research indicated that only about 1% to 5% of people exposed to the bacteria get infected. People contract Legionnaire’s disease through the inhalation of contaminated droplets of water which results in pneumonia-like symptoms. Once inhaled, it enters the lungs, settles and grows in surrounding tissue. Contraction of the disease is influenced by sex - men are more susceptible than women; age - people older than 50 are more susceptible; addictions - smokers and people who abuse alcohol and drugs are more at risk; and existing health conditions – immune-compromised people with Aids and/or TB are at high risk. The symptoms: • Similar to flu, including − High fever − Chills − Headaches − Muscle pain − Dry cough − Difficulty in breathing − Diarrhoea − Vomiting − Confusion or delirium Where is the bacteria found? • Legionella is present in natural water environments and soil. • It can also be found in evaporative condensers, spa baths and hot and cold water systems such as showers. It can also be found in/on: − Hot and cold water tanks. − Warm water at temperatures between 20°C and 45°C. − Pipes with little or no water flow. − Slime and dirt on pipes feeding showers. − Taps. − Tank surfaces. − Rubber and natural fibres in washers and seals of plumbing materials. − Water heaters and hot water storage tanks. − Scale in pipes, showers and taps. In an effort to reduce electricity usage and save money, many South Africans have been turning their attention to optimising the use of electric geysers - the appliance that accounts for up to 50% of electricity consumed in an average household. Savings have been achieved by either switching the geyser off for long periods or adjusting the thermostat. This led to many homeowners questioning whether these two practices could, possibly, contribute to hot water bacteria growth in geysers, potentially harmful to people. Eskom undertook extensive research to ascertain the facts.