Although manufacturer's usually set water heaters at 60C, you can reduce your carbon footprint and save money by adjusting your boiler's hot water thermostat. Each four degree reduction in water temperature could save you around three to five per cent in energy costs. Setting your hot water temperature to 50C at the tap also reduces the danger of scalding.
Inhaling water vapour contaminated with Legionellosis bacteria causes pneumonia-like symptoms that can kill you if left untreated. A hot water setting of 60C in hotels, hospitals and other large public buildings can control Legionnaires' disease. However, there is less danger of bacterial growth in smaller domestic hot water tanks. Consequently, the minimum water heater outlet temperature in residential systems should be set at 54C to produce a tap temperature of at least 49C.
Test water temperature
Water heater thermostats are not very accurate and there is some heat loss between the hot water tank and the tap. Place a deep glass under the hot water tap farthest from the heater. Run the water for a minute or two to heat up the pipes and the glass. When the water reaches maximum temperature, drop a cooking thermometer into the glass to get an accurate reading. Reduce the thermostat setting on your water heater by the appropriate amount. For example, if the delivery temperature is 53C, lower the thermostat by 4C to 5C.
Set your thermostat
Electric storage tank type hot water heaters are often fitted with two thermostats -- one at the top, and one at the bottom of the tank. Turn the power to the hot water heater off by tripping the relevant breaker switch on your home's electrical fuse box. Remove the upper and lower metal inspection covers with a screwdriver and push the insulation aside to reveal the thermostats. Insert a flat screwdriver into the screw surrounded by a temperature dial and adjust it to the desired setting. Replace the inspection plates and restore the power. Hot water tanks supplied by a gas boiler are usually fitted with an exposed adjustable knob, but this could also be hidden behind an inspection plate. Turn the knob until the arrow points to the desired temperature. Drain off some hot water to get the heater working again, and retest the taptemperature after an hour.