Temperature plays an important role in legionella bacteria control and management as the legionella bacteria can proliferate between 20-50°C and has even been known to grow at 54°C, with legionella’s most favoured temperature being 37°C (body temperature) which is why it can be dangerous to humans once contracted causing illness such as legionnaires disease, pneumonia, Pontiac fever, and the common cold and flu. In many ways monitoring data to ensure you fall into these water quality parameters is one of the best ways to ensure your water systems meet regulations.
Temperatures must be reached within a specific timeframe. This allows us to ensure temperature testing remains consistent and allows us to determine the frequency of use of the outlet and potential areas of stagnation or risk.
Temperatures are required to be taken from all heat sources and the sentinel points of a water system. Sentinel points are the monthly temperature points at the nearest and furthest outlets of each water system. For example, taking the sentinel points from a cold-water storage tank would consist of taking the temperature from the nearest tap to the tank and the furthest away. For heat sources, this means taking the temperatures nearest and furthest from all heat sources. This may be a cylinder, electric water heater, boiler or otherwise. However, in the case of an instant water heater with a single outlet such as a shower, the outlet becomes the nearest and furthest so one temperature would be all that can be taken.
Hot temperature – 1 minute
Cold temperature – 2 minutes
Hot outlet – 50°C (55°C in healthcare)
Cold outlet – <20°C
TMV* outlet – 38-43°C (ranges vary for showers/baths)
Scalding – 44°C
Cylinder and flow – 60-65°C
Cylinder return – 50°C (55°C in healthcare)
Combination water heater – 60-65°C
Boiler – 50-60°C (55°C minimum in healthcare)
Electric water heater – 50-60°C (55°C minimum in healthcare)
Instant water heater – 50-60°C (55°C minimum in healthcare)
*TMV – thermostatic mixing valve, blends hot and cold to create a reduced, non-scalding temperature. Often required for vulnerable persons and in healthcare.