Monitoring temperature of your water distribution system is undertaken to check that the facility water distribution system is operating at optimal temperatures to control microbial growth, minimise biofilm development and demonstrate compliance with your water risk management plan (WRMP).
It must be noted that in Queensland, during the warmer months in the south, and for most of the year in tropical regions, the temperature of incoming water from the town water supply is likely to be elevated (in the range from 25-32 degrees C). It is therefore unlikely that cold water could be maintained at temperatures that would suppress Legionella growth (i.e. below 20 degrees C). This puts more emphasis on other operational controls including disinfectant residual and stagnation control.
Effect of temperature on Legionella survival and growth
Legionella can grow and multiply between 20 and 45 degrees C, with optimal Legionella multiplication occurring at approximately 37 degrees C.
Legionella can survive temperatures greater than 45 degrees but is unable to multiply.
After approximately 2 minutes at 65 degrees C, 32 minutes at 60 degrees C and 6 hours at 55 degrees C Legionella is killed.
Immediate disinfection of Legionella occurs at 70 degrees C.
It should be noted that the time for a third degree burn to occur is 1 second at 60 degrees C, 10 seconds at 55 degrees C and 5 minutes at 50 degrees C.
This emphasises the importance of monitoring and maintaining the appropriate water temperature in both water storages and at delivery points within a healthcare and residential aged care facilities.
When to undertake temperature checks
Water temperature checks of cold, warm and hot water outlets and storages should be taken at the frequency as detailed in your WRMP.
Operational exceedances, events or situations that may require more frequent temperature checks should be noted in your WRMP and could include, but not be limited to:
- water temperature outside a set critical limit or range
- extended periods of hot weather (due to heating of cold water supplies)
- extended periods of hot water use (capacity of heater to cope)
- any outlet which has not been used for more than 5 days (as water may have cooled or warmed to undesirable temperatures)
- other disruptions that may cause changes in water temperatures (e.g. plumbing maintenance or an interruption to supply event).
Where to undertake temperature checks
Temperature checks need to be taken that are representative of the system performance. For this reason selecting representative temperature sampling points is important.
Temperature checks should be taken, for hot, warm and cold water, at the most distal points in a water distribution system; at or immediately downstream of hot water storages (to check that temperatures above 60 degrees C are consistently met); and at any location in the cold water distribution system where external heat sources may increase cold water temperatures to levels favourable to Legionella proliferation.
Hot or warm water from a system that has a flow and return loop:
Take a minimum of 3 temperature checks from each loop or building wing. If the building has multiple floors on a single loop, take 3 temperature checks per floor. One temperature check should be taken from an outlet located close to the start of the flow loop exiting from the hot water supply. Another temperature check should be taken from an outlet located approximate mid-point in the flow loop. The final temperature check should be taken from an outlet location close to the end of the flow loop, prior to the return to the hot water supply.
Hot or warm water from a system that has no flow and return loop:
Take a minimum of 3 temperature checks from each hot or warm water system. If the building has multiple floors with single hot/warm water distribution systems, then take 3 temperature checks per floor. One temperature check should be taken from an outlet located close to the hot water supply (proximal sample). Another temperature check should be taken from an approximate mid-point in the system. The final temperature check should be taken from an outlet location close to the furthest point from the hot water supply (distal sample).
Take a minimum of 3 temperature checks from each system or building wing. If the building has multiple floors, take 3 temperature checks per floor. One temperature check should be taken from an outlet location close to the entry point from the mains incoming cold water supply (proximal sample). Another temperature check should be taken from an approximate mid-point in the system. The final temperature check should be taken from an outlet location close to the furthest point from the mains incoming cold water supply (distal sample).
Who should undertake temperature checks
Temperature checks should be undertaken by competent staff. A workplace health and safety officer should be consulted before carrying out temperature checks as personal protective equipment (PPE) may be required (scald protection).
Main steps for monitoring temperature should meet the following criteria:
- For hot water storage heaters, record the temperature of the stored hot water as shown on the heater temperature gauge (if fitted). If no temperature gauge is fitted then the temperature can be checked by operation of the heater’s temperature relief valve. Alternately, locate the nearest hot water outlet fed by the heater to record the temperature.
- For cold water storages, record the temperature by partially opening the tank’s drain valve and record the temperature at the discharge into the drain. Alternately, locate the nearest cold water outlet to the storage tank to record the temperature.
- For tap outlets the procedure is the same for both the hot or cold water supplies:
- Run the outlet for 60 seconds to allow the water to reach a stabilised temperature. Note that some hot water outlets may take longer to reach a stabilised (maximum) temperature.
- To get an accurate temperature run the water into a cup or glass and let it overflow into the sink or basin.
- Put the thermometer into the cup and record the temperature once it has stabilised.
- In some instances hot water supplies may fluctuate in temperature during sampling. This could be due to the type of hot water heater installed (e.g. instantaneous heater), or that tempering or thermostatic mixing valves (if installed) are in need of service or replacement.
- If temperature fluctuations occur, note the maximum and minimum temperatures attained.
- Once completed, ensure the outlet is turned off and any water splash is mopped up.
See control measures information sheet for possible control measures for maintaining water temperature within acceptable limits.
In accordance with your WRMP, when carrying out temperature checks, ensure you record which outlet was checked for temperature (e.g. shower, hot water tap), by whom, the location, date and time and any additional comments (variable temperature).
- Stringent control measures must be implemented to prevent the risk of scalding.
- Throughout the temperature recording process, exposure of staff, patients or residents to aerosols should be minimised.
- Record the locations of temperatures that take longer than 60 seconds to stabilise. These outlets should be checked to ensure that the cause is due to the pipe being a long run and not due to an obstruction in the pipe or faulty equipment (e.g. circulation pumps or faulty heating systems).
- National enHealth guidelines for Legionella control (PDF, 577KB) – section 3.2 (page 25-27).
- UK Department of Health Technical Memorandum 04-1 (2006): The control of Legionella hygiene, “safe” hot water, cold water and drinking water systems. Part B: Operational management.
- UK Health and Safety Executive (2013) L8 Legionnaire’s disease. The control of Legionella bacteria in water systems.
- World Health Organisation (2007). Legionella and the prevention of Legionellosis.
- World Health Organisation (2011). Water safety in buildings.