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The temperature of water within cold water pipes should not be warmed above 25ºC and ideally not above 20ºC. Adequate measures should be taken to ensure that this temperature is not exceeded.
Defra guidance states that hot water should be stored at a temperature of not less than 60ºC and distributed at a temperature of not less than 55ºC. This water distribution temperature may not be achievable where hot water is provided by instantaneous or combination boilers.
Where practicable it should also reach your tap and be at least 50ºC within 30 seconds after fully opening the tap. This criteria may not be achievable where hot water is provided by instantaneous or combination boilers.
Each month more than 200 children are admitted to an NHS Burns Service following injuries with hot liquids. The majority of burn and scald injuries happen at home, and mainly in the bath. (According to the Children’s Hospital in Bristol about 30 per cent are linked to baths and showers. Find out more from the Children’s Burns Trust.)
One of the main reason scalding occurs is that hot water is stored at 60°C or above to limit the growth of harmful microrganisms, such as Legionella bacteria. But if water comes out of the tap above 60°C, people can suffer third degree burns in just six seconds.
WaterSafe recommends using a qualified plumber who will advise on the use of thermostatic mixing valves (TMVs) with taps or showers to reduce the risk of burns and scalding. These devices should be maintained annually.
TMVs allow water to be stored at a high enough temperature to kill harmful microorganisms, but reduce it to a safe temperature at the point it comes out of the tap or shower, by mixing it with the cold water supply. TMVs also maintain the pre-set, safe temperature even when water pressure fluctuates as other appliances are used. TMVs will shut down the flow if the hot or cold water supply fails.
Note: Care needs to be taken that adding TMVs does not lead to problems with microorganisms, so TMVs should be installed close to where they will be used to minimise the length of pipework the water will pass through at a reduced temperature.
Hot Water Burns Like Fire is a campaign to stop scalding by hot water from taps and showers. Visit their website for more information on how to minimise the risk of burns and scalding.