1:5:10:365 EcoTip Blog

November 11, 2008

316: Scald Prevention

Take the 1:5:10:365 challenge: Do one thing – for 5 to 10 minutes – 365 days a year to make our home and planet environment better.

1:5:10:316 EcoTip: Install a scald prevention system. This allows your hot water heater to operate at a high enough temperature to prevent Legionella pneumophilia from growing in your hot water system, but automatically mixes cold water to a preset temperature for safety. A scald prevention valve at each hot water fixture then acts as an extra safety device to shut-off the water flow as a fail- safe should the temper valve stop working.

anti_scald_domesticTemper valve



 Additional Information:

Suggested Review: :146

Anti-scald devices are now required by U.S. law in all new plumbing installations. An anti-scald device shuts the water off when the temperature exceeds 120°F (49°C) but it doesn’t temper the water temperature. This means that in the U.S. the water heater is frequently used to keep the temperature low. 

Lower temperatures save energy and help prevent scalds but they may also lead to the growth of Legionella pneumophilia  in the hot water heater. These conflicting issues are discussed in :146.

According to the Washington based National Coalition to prevent childhood injury tapwater scald injuries are the second most common cause of serious burn injuries and are responsible for over 100 deaths a year in the United States (mostly children under 5 and elders over 65)

According to the Austrailian green plumbing firm Highlander Plumbing the following regulations apply in Austrailia (but the information is valid anywhere):

AS 1056.1
With reference to clause 3.2.2 the thermostat for a storage water heater shall be set at not less than 60°C. This clause then explains that a minimum setting of 60°C is specified on the advice of the Department of Health, NSW, that bacteria Legionella pneumophillia do not survive in temperatures above 55°C.

AS 3500.4
With reference to Clause 1.10.2, Part B, all new hot water installations shall deliver hot water not exceeding 50°C in residential buildings, at the outlet of all sanitary fixtures used primarily for personal hygiene purposes.

Here are the facts:…

  • at 50°C, a deep scald takes 5 minutes in an adult or child;
  • at 54°C, a deep scald takes 35 second in an adult and 10 seconds for a child;
  • at 60°C, a deep scald takes 6 second for an adult and 1 second for a child;
  • at 65°C, 2 seconds for an adult and 0.5 seconds for a child;
  • at 70°C, in a typical factory setting – 1 second for an adult.

Tempered water is compulsory on all new residential developments in NSW. You cannot simply turn the heater down or you will breed Legionella. The tank must stay hot, but the water coming out must be tempered down.

*A tempering valve has on average a 5yr lifespan and cannot be serviced. We recommend replacement after 5 yrs. This valve is a safety valve and cannot be serviced. If the valve fails to operate it is to be replaced.

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