Legionella Control in Hot and Cold Water Systems

Hot and Cold Water Systems

Hot and cold water systems in buildings supply fresh water for cooking and cleaning and other functions such as heating.

Systems that supply hot and cold water range in size scale and complexity.

Water is usually distributed throughout buildings through a pipework system.

Hot and cold water systems need careful management, particularly in public buildings such as healthcare premises to reduce the risk exposure to legionella.

Legionella bacteria is responsible for Legionnaires’ disease, an uncommon but serious lung condition.  It can be caught by inhaling droplets of water from hot tubs, shower heads or heating systems.

Temperature control of hot and cold water systems plays an important part in reducing the risk of legionella bacteria within the system.

Where possible, cold water systems should be maintained at a temperature below 20°C.  Stored hot water temperatures should be at least 60°C.  Guidelines for temperature control state that hot water distributed from stores should reach the outlets within one minute and be at a temperature of 50°C or 55°C for healthcare premises.

Cold Water Systems

Storage tanks should be checked to make sure there is a continuous flow of cold water to avoid stagnation.  Ideally, the volume of water stored should be sufficient for one day’s usage.

Water temperatures flowing into storage tanks should be checked to make sure the temperature remains less than 20°C.  A convenient place to measure this is at the ball valve outlet to the cold water tank.  Comark’s legionella testing kits have special probes that fix round pipes with Velcro.  This makes it easy to get accurate and consistent measurements very time.

Hot Water Systems

Taps and showerheads can be tested by running water for two minutes at sentinel taps.  The water temperature should be below 20°C.  This is a useful annual check that should be taken to to ensure that the supply and flow of cold water remains at a temperature that will not encourage the growth of legionella.  Outlets throughout the system should be covered over a period of time to ensure a full assessment of the system.

For hot water storage, visual checks can be undertaken to check the quality of the stored water.  This will help make an assessment of the tank cleanliness and whether there is any sludge, scale or other contamination present.

In order to kill legionella bacteria, hot water should be stored at a minimum of 60°C.  Again, temperatures should be checked as part of a system assessment.

In the United States of America, monitoring water quality parameters are set by state regulations or codes so you should check the recommended testing temperatures for your area.