Home Forums General Discussion Hot water temperature recommendations Reply To: Hot water temperature recommendations

Ian McChesney

Hi Michael
Very interesting question you pose, and can be quite tricky to get the ‘best’ solution. As Scott says, we need to be particularly careful with delivery temperatures for elderly and the very young. Indeed the delivery temps for early childhood centres, schools, old people’s homes, hospitals is 45 degrees, not the 55 degrees for homes. And in many countries the delivery temp for homes is 48 degrees. Above 55 degree the burning risk goes up exponentially with temperature, so for any at-risk part of the population this is not a trivial matter.

Fitting tempering valves would likely be a very expensive option as noted, so the thermostat adjustment would be the first approach. But many older hot water systems that are low pressure and/or have small cylinders rely on high HW cylinder temperatures to get (a) sufficient hot water storage, and/or (b) a satisfactorily warm shower. As Phil notes, you may find that reducing the HW cylinder temperature compromises hot water services.

Tempering valves also have technical requirements for minimum operating pressures and minimum temperature differentials between the cylinder and the outlet. In some houses it may be quite difficult to achieve the minimum pressure requirement. And, ironically, you may have to turn up the temperature in the HW cylinder to achieve the minimum temp differential.

I would recommend you suss out a highly recommended local plumber or two and go and talk to him/her about the options. They should have some good, practical advice to offer.

A final point about energy saving from turning down temperatures. In general, for smallish temperature changes, turning down the temperature saves little. There will be some reduction in standing losses from the HW cylinder, but the difference from 60 to 55 degrees will likely be around 120kWh/yr for an unwrapped B or C cylinder (maybe $30/yr?), and less for wrapped or A grade. Regarding hot water use – given that most hot water end-uses are actually for warm water around 35-50 degrees and so rely on some mixing with cold water, unless the total amount of warm water use changes, one just ends up changing the mixing ratio of hot:cold water to achieve the same end-use, and the energy use will be the same.