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13) Water Services

The main areas of risk are with scalding from hot water and Legionella infection from stored hot water. Hot water

temperatures that do not cause scalding are ideal for the Legionella bacteria to grow in a water system, but hot water temperatures that kill the Legionella bacteria will cause scalding.

The risk increases rapidly as water temperature increases above 45°C, for example, partial thickness burns will occur within 30 seconds at 55°C, reducing to less than five seconds

at 60°C and above.

What are the maximum water temperatures for safe use in healthcare premises, care homes, schools

and leisure facilities?

  • For an unassisted bath 44°C
  • For an assisted bath 46°C
  • For shower applications 41°C
  • For wash basin applications 41°C
  • For bidet applications 38°C

What are Legionella bacteria?

These are naturally occurring organisms present in many water systems. If humans are exposed to large quantities of these organisms they can cause the development of Legionnaires’ Disease, causing respiratory problems which can be potentially fatal.

Legionella bacteria will not multiply in temperatures below 20°C so the temperatures of cold water in storage

cisterns should not be allowed to exceed that temperature.

The bacteria proliferate between 20°C and 45°C, but will die at temperatures above 60°C. Water supplies should be distributed to the point of mixing at below 20°C for cold and above 55°C for hot supplies, and hot water should be stored at or above 60°C.

What should be the objective of the controls on a hot water system?


A. To store the water at above 60°C, distribute the water at 55-60°C, yet deliver the water at safe discharge


The most effective means is to store and distribute the hot water at high temperatures and use thermostatic mixing

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