Whenever I install a control pad to an instantaneous gas hot water system for a customer who has never had one before, the first thing they want to know is what temperature they should set it at for showering. Trial and error will quickly determine that for them but as a rough guide I say 48° in winter and 42° in summer.

I’ve run into several customers who have been cursed with a hot water unit preset to deliver water no hotter than 50° and it drives them bananas. While this is plenty hot enough for showering, it isn’t satisfactory for dishwashing.

The Australian national plumbing code introduced rules relating to the temperature of water delivered from every hot tap in Australia while I was doing my apprenticeship in the mid 90s. I don’t personally know anybody who ever got burnt by water coming out of a hot tap, but evidently scalding and burning is enough of a problem that the standards committee decided to implement changes to the plumbing code to reduce the incidence of burns and scalds in Australia. These hot water tempering requirements have affected every house built in Australia ever since and I sometimes get asked by people about why they have a tempering valve or why the hot water in the kitchen isn’t hot enough to wash dishes.

The reason why people end up with a kitchen hot tap that will not deliver water hotter than 50° is because their hot water installation is both technically compliant and cheap and nasty. The code requirement stipulating that hot water shouldn’t exceed 50° at outlets used for ablutions is found in AS 3500.4:2003 clause 1.9.2 shown below.

AS3500.4:2003 clause1.9.2

AS3500.4:2003 clause1.9.2

Some plumbers submit to the unrealistic cost cutting wishes of customers and make every hot water outlet in the house unable to deliver more than 50° because it saves the cost of supplying and installing a temperature control pad in the case of instantaneous hot water systems. If you’ve become stuck with an instantaneous hot water unit preset to 50° serving your whole house, you’ve been dudded big time and your only solution is to replace the unit and install temperature control pads if your water heater is restricted to heat only to 50°.