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.

The research conducted by Eskom involved taking water samples from a number of sources, which included ‘hot water technology sources’ such as electric element geysers, solar water heaters and heat pumps; and ‘actual water sources’ such as borehole water, municipal water and storage tanks. The water samples were then sampled at different temperature ranges and their microbiological and chemical properties tested.

Findings:• Water source points currently used for drinking water contained Legionella.

• Legionella is present in water in hot water systems at temperatures between 49°C and 55°C, but decreases over time when the water is kept at this temperature.

• The most effective treatment against Legionella is to keep cold water cold and hot water, above 55°C.

The incidence of contracting legionella-borne infections is between 1% and 5% and, therefore, very low.

By taking basic precautions households can protect themselves against the risk of water-borne bacterial infections.

Full information on Eskom’s rebates and incentives on energy saving solutions for the homeowner – including solar geysers and heat pumps - is available at www.eskom.co.za/idm.

Eskom research findings and recommendations:

• Water temperature in hot water tanks should be kept at a minimum of 55°C (for heat pumps), optimally at 60°C.

• Water at the outlet points of hot water cylinders should be above 50°C within a minute.

• Cold water should be less than 20°C.

• At each outlet point it should be below 20°C within 2 minutes of running the water.

• Tanks should be insulated and closed.

• Shower heads and hoses should be dismantled and cleaned to remove scaling.

• Any unit, such as a shower head not used regularly, should be flushed and purged with water before use. Water must run freely through the shower head with hot water for a few minutes before getting in the shower to ensure that the shower head and pipes have been flushed effectively.

• Borehole water must be sterilised or filtered to prevent Legionella and bacteria growth in drinking water.

Recommendations:

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www.eskom.co.za/idmIssued by Eskom Integrated Demand Management June 2012 Eskom Holdings SOC Limited Reg No 2002/015527/06