The ideal temperature setting for your hot water cylinder is 60°C, to kill bacteria, any higher is a waste of energy.
The New Zealand Building Code states that in the home the maximum water temperature at the tap for showers, baths and handbasins is 55°C so you may need a tempering valve installed. In some places the temperature must be no higher than 45°C at the tap.
Hot water cylinder temperature
Many people set the temperature of their hot water cylinder too high. The ideal setting is 60°C. It is important that the water in the cylinder is this hot to kill bacteria such as legionella but higher temperature settings only increase your power bill and can scald you (it only takes one second at 70°C).
You can find the thermostat under the protective lid on the side of or underneath the cylinder. It can usually be adjusted with a screwdriver. Many thermostats are not very accurate so you should test that the water comes out of the tap with a thermometer.
In most instances the maximum temperature of hot water supplied to sanitary fixtures provided for personal hygiene (e.g. showers, baths, hand basins) is 55ºC. This can be achieved by fitting a tempering valve to your cylinder. However, hot water to the kitchen and laundry may be at cylinder temperature.
The Building Code states that the maximum temperature at the tap is 45ºC for places such as childcare centres; schools; old people’s homes; etc. If there are young children in your home you might want to consider adjusting your tempering valve on your hot water cylinder to lower the temperature to 45°C at the tap. This is a safe water temperature for children, ensuring they don’t get burned. Ask your local energy supplier or a licensed plumber for advice on how to adjust it, if necessary. Always ensure that the thermostat and element covers are in place on your cylinder to prevent electric shock.