Using IoT LoRaWAN to monitor hot and cold water services in medical centres

What is legionella?

Legionella bacteria is commonly found in water. The bacteria multiply where temperatures are between 20-45°C and nutrients are available. The bacteria are dormant below 20°C and do not survive above 60°C.

Legionnaires’ disease is a potentially fatal type of pneumonia, contracted by inhaling airborne water droplets containing viable Legionella bacteria. Such droplets can be created, for example, by hot and cold water outlets, showers etc.

Anyone can develop Legionnaires’ disease, but the elderly, smokers, alcoholics and those with cancer, diabetes or chronic respiratory or kidney disease are at more risk.

What you need to do

Healthcare providers should carry out a full risk assessment of their hot and cold water systems and ensure adequate measures are in place to control the risks.

Using temperature control

The primary method used to control the risk from Legionella is water temperature control. Water services should be operated at temperatures that prevent Legionella growth:

·         Hot water storage cylinders (calorifiers) should store water at 60°C or higher *see note 1

·         Hot water should be distributed at 50°C or higher (thermostatic mixer valves need to be fitted as close as possible to outlets, where a scald risk is identified). *see note 1

·         Cold water should be stored and distributed below 20°C. *see note 1

‘Sentinel’ outlets must be identified (furthest and closest to each tank or cylinder) for monthly checking of the distribution temperatures.

You should also check the hot water storage cylinder temperatures every month *see note 1

You should also check the cold water storage tank temperatures at least every six months. *see note 1

Stagnant water favours Legionella growth. To reduce the risk you should remove dead legs/dead ends in pipe-work, flush out infrequently used outlets (including showerheads and taps) at least weekly and clean and de-scale shower heads and hoses at least quarterly. Cold-water storage tanks should be cleaned periodically and water should be drained from hot water cylinders to check for debris or signs of corrosion.

Design systems to minimise Legionella growth, by:

·         keeping pipe work as short and direct as possible;

·         adequately insulating pipes and tanks;

·         using materials that do not encourage the growth of Legionella;

·         preventing contamination, eg by fitting tanks with lids and insect screens.

Additional controls

Water samples should be analysed for Legionella periodically to demonstrate that bacteria counts are acceptable. The frequency should be determined by level of risk, in accordance with the risk assessment.

Other control methods

Other methods to control Legionella include copper and silver ionisation and biocide treatments (eg chlorine dioxide). To ensure that they remain effective their application will need suitable assessment as part of the overall water treatment programme including proper installation, maintenance and monitoring. *see note 1

Hot Water Storage Cylinder

·         The cylinder should deliver outgoing water at a temperature of at least 60°C and a gauge should be fitted at the outlet of the cylinder to ensure this is being achieved *see note 1

·         The hot water circulation loop should be designed to give a return temperature to the cylinder of at least 50°C and a gauge should be fitted at the return to the cylinder to ensure this is being achieved. *see note 1


Hot and Cold Water Distribution System

·         The water temperature at the hot outlets should be measured, at least monthly, to ensure it reaches at least 50°C within a minute of running the water. If thermostatic mixing valves are fitted the temperature of the hot inlet pipe, just prior to the TMV, should be measured to ensure it reaches at least 50°C. *see note 1

·         The water temperature at the cold outlets should be below 20°C after running the outlet for up to two minutes *see note 1



It is essential that the control measures identified are maintained long term to minimise bacterial growth. In addition:

·         records of temperatures at cylinders, tanks and sentinel outlets (i.e. nearest and furthest outlets on each loop or run) should be kept. *see note 1


Note 1 - Click this link to see details on our LoRaWAN easy to install temperature probe. No cables required and batteries typically last for up to 5 years with hourly temperature readings recorded. 

External Temperature Probe

This temperature probe has many applications. It can be bonded to pipework to monitor hot and cold liquid temperatures, heating, refrigeration, milk etc or deployed in air to monitor freezer conditions.

Example uses:

  • Hot water cylinders, bonded/strapped to the cylinder or flow pipework.

  • Process pipe work. Flow & return temperature. fitted into stainless steel sensor pocket or strapped to pipework

  • End of Line pipework temperature monitoring  


About Ver Facil Limited

With many years experience in designing, installing and maintaining Building Management Systems with comprehensive hot & cold water monitoring system, Ver Facil Limited is using the latest LoRaWAN technology to radically lower the installation costs for End of Line (EoL) temperature monitoring.