Solar Hot-water Heaters and Legionella Bacteria
By law, commercial solar hot-water heaters have to be fitted with a temperature sensor inside the tank. When the system detects that Legionella bacteria may be present, a valve automatically closes so that water cannot be removed from the tank. Alternatively, an external heater can be triggered to heat the water enough to kill the bacteria.
Recent Legionella outbreaks in Australia
A recent Legionella outbreak in Brisbane has highlighted the importance of carefully monitoring temperature variations in hot water systems.
One patient died and a number of patients had to be transferred to other hospitals following the outbreak. It is suspected that lowering the temperature of hot-water systems in line with Workplace Health and Safety to prevent burns occuring to patients has contributed to an increase in Legionella outbreaks throughout the world.
To remove the bacteria from the water pipes it was necessary to increase the water pressure, raise the hot-water temperature to 65 degrees and run all the taps and showers in the hospital for 10 minutes! Check the table in the Explore section. Is this enough?
Can you find any news reports of other cases of Legionella outbreaks in Australia and elsewhere?
The System Being Studied at La Trobe
The solar hot water heater in this FARLabs experiment is also being studied by university students at La Trobe. Below are the notes which guide the students through their experiments. You may find them of interest. The task involves some programming, but is within reach of an interested year 11 or 12 student. The notes also contain useful background information which both teachers and students might find useful.