The key factor in preventing legionella is the temperature of the water in your installation. With central heating systems, hot-water pipes must reach 60°C. Cold-water pipes must remain below 20°C. The return pipe to the heater must ensure a water temperature of at least 50°C.

Possible issues include:

• insufficient insulation of pipes

• hot and cold water circuits placed too close together

• long distance between the heating point and the draw-off point

• insufficient capacity of the boiler or storage tank

• insufficient circulation flow rate in circulating circuits

• storage tanks, boilers, shower heads and tap heads not cleaned or descaled regularly

• water stagnation in pipes.

The high temperature of the hot-water circuit requires the general use of thermostatic taps.

Flushing the pipes with hot water is an effective method. The bacteria die quickly (around 3 minutes) at 70°C. Therefore, it is recommended to flush the circuit with water at 70°C for 5 minutes, or with water at 60°C or higher for 20 minutes – meaning effectively between 60°C and 70°C at the draw-off point.