Why 50 or 60 Degrees? Hot Water Temperature Rules Explained
Hot water temperature in Australia comes down to two numbers. One stops Legionella. The other stops scalds. They are not the same number, and that is the whole story.
In Australia, hot water delivered to bathroom outlets in a home must be no hotter than 50 degrees, while a storage hot water tank must keep its water at 60 degrees or more to stop Legionella bacteria growing. The 50 degree rule protects skin. The 60 degree rule protects lungs. A storage system has to satisfy both, so it heats to 60 and uses a tempering valve to bring the bathroom supply back to 50. An instantaneous or continuous flow unit stores no water, so most can simply be set to 50 and skip the valve. Your plumber applies the exact rules for your state and your building.
Want your exact size? Our instant hot water sizing calculator works out the kW or litres a minute you need in winter, checks single or 3-phase power, then shows the units that fit.
Why bathroom hot water is capped at 50 degrees
Bathroom hot water is capped at 50 degrees in Australian homes because water hotter than that burns skin fast, and the people burnt most often are small children and older adults. The plumbing standard (AS/NZS 3500.4) sets the 50 degree limit for outlets used for personal hygiene in new and replacement installations.
The burn times are the reason nobody argues about it. These are the figures safety groups commonly quote for adult skin. Children's skin burns in a fraction of the time.
| Water temperature | Time to a serious burn (adult skin, approx.) |
|---|---|
| 70°C | under 1 second |
| 60°C | about 1 second |
| 55°C | about 10 seconds |
| 50°C | about 5 minutes |
Approximate figures, commonly cited by Australian child safety organisations. Children and elderly people burn much faster.
One second versus five minutes. A toddler who turns the hot tap in the bath has time to be pulled out at 50 degrees. At 60 they do not. That is the entire argument, and it is a good one.
Schools, childcare centres, aged care and hospitals usually go lower again, typically 45 degrees, often through a thermostatic mixing valve. Your plumber or hydraulic consultant sets that, not the heater box.
Why storage tanks must store water at 60 degrees
A storage hot water tank must hold its water at 60 degrees or above because Legionella bacteria multiply in warm, still water between roughly 20 and 45 degrees and are killed off at 60. A tank kept at 50 is a warm incubator sitting in your backyard.
So a storage system has a problem. It must store at 60 for hygiene but deliver no more than 50 to the bathroom for safety. Heat pump, electric storage and gas storage tanks all live with this conflict. The fix is a valve.
What a tempering valve does on a hot water system
A tempering valve blends hot water with cold water so the water leaving it for the bathrooms never exceeds 50 degrees, whatever temperature the heater stores or produces. It sits on the hot water line near the heater and is set and sealed by the plumber.
- Where it goes: on the hot line feeding bathrooms and ensuites. The kitchen and laundry are often left on the hotter, unmixed supply.
- Cost: the valve itself is usually a modest part of the install, but it adds labour and it needs checking.
- Maintenance: tempering valves wear. Most manufacturers recommend a check by a licensed plumber every 5 years or so. A failed valve can drift hot or cold.
A tempering valve is not the same as a thermostatic mixing valve (TMV). A TMV holds the temperature more tightly and shuts off hot water if the cold supply fails. TMVs are the usual choice in care settings. Homes generally use a tempering valve.
Instant hot water at 50 degrees: no tempering valve needed
An electric instantaneous or gas continuous flow heater preset to 50 degrees generally needs no tempering valve, because it stores no water for Legionella to grow in and it never produces water hotter than the bathroom limit. That removes one part, one install step and one future service call.
Most of the units we sell are built around this. The table shows the maximum outlet temperature of each one, straight from the spec sheets.
| Unit | Type | Temperature setting | Tempering valve? | Price |
|---|---|---|---|---|
| Midea M20, 50°C preset | Gas continuous flow | Preset 50°C, 38 to 48°C with optional controller | Not for the 50°C preset | $749 |
| Midea M26, 50°C preset | Gas continuous flow | Preset 50°C | Not for the 50°C preset | $849 |
| Stiebel Eltron DHC-E 8/50 | Electric, single phase | 40, 45 or 50°C | No | $915 |
| Stiebel Eltron DEL 27 Plus | Electric, 3 phase | 20 to 50°C | No | $1,399 |
| Midea M20, 70°C preset | Gas continuous flow | Preset 70°C | Yes, required | $749 |
| Stiebel Eltron DHE 27 | Electric, 3 phase | 20 to 60°C | Depends on setting and outlets served | $1,545 |
Prices current as of October 2026, AUD including GST, unit only. Installation not included.
If the unit only feeds showers and basins, buy a 50 degree model and be done with it. There is no prize for owning more temperature than the law lets you use in a bathroom.
When 60 or 70 degree hot water makes sense
60 or 70 degree hot water makes sense when the unit feeds a kitchen, laundry or commercial sink that genuinely needs hotter water, or when it serves as a booster that has to reach storage temperature. For a normal house bathroom it is the wrong choice.
- Commercial kitchens and cafes. Hotter water for washing up and cleaning. The bathroom side still gets tempered to 50.
- Kitchen sink only, point of use. The Stiebel Eltron DHC-E 8/60 runs 38 to 60 degrees on single phase for exactly this job, at $915.
- Precise 3 phase control. The Stiebel Eltron DHB-E 18 LCD sets 20 to 60 degrees on a digital display, at $1,139.
- Multi zone houses. A 70 degree gas unit feeding the kitchen hot, with a tempering valve on the bathroom branch.
The 70 degree Midea models are the ones people buy by accident. The M20 70°C preset costs the same $749 as the 50°C preset, and it requires a tempering valve. Order the wrong one for a bathroom only install and your plumber either adds a valve or sends the unit back. Check the variant before checkout.
Boiling water units sit outside the 50 degree rule
An undersink boiling water unit feeds a dedicated boiling water tap, not a bathroom outlet, so the 50 degree bathroom limit does not apply to it. The Stiebel Eltron HOT 2.6 N heats a small tank for near boiling water at the kitchen sink, priced at $878. These taps need a child safety feature and a sensible install position. They are a kitchen appliance, not a hot water system.
Getting the temperature wrong: the usual mistakes
The most common hot water temperature mistakes are turning a storage tank below 60 to save power, ordering a 70 degree unit for bathrooms, and expecting a 50 degree heater to fill a bath faster than it can. All three come up on our phone line every month.
- Turning the storage tank down to 50. It saves a little power and grows Legionella. Leave the tank at 60 and let the tempering valve do its job.
- Buying 70 degrees for a shower. More temperature does not mean more hot water in the shower. The valve mixes it back to 50 anyway.
- Blaming the 50 degree cap for weak winter showers. A shower runs about 40 degrees. A 50 degree limit is plenty. A lukewarm winter shower is a flow rate problem, not a temperature setting problem. Our guide to hot water flow rate in litres per minute explains why.
If you are weighing up whether to keep a storage tank at all, the trade offs are in our instant hot water vs storage tank comparison.
Frequently asked questions
Why is hot water limited to 50 degrees in Australia?
Hot water is limited to 50 degrees at bathroom outlets in Australian homes to prevent scalds, because water at 60 degrees can cause a serious burn in about one second while water at 50 degrees takes about five minutes. The limit applies to new and replacement installations under the plumbing standard AS/NZS 3500.4.
Why does a hot water tank need to be 60 degrees?
A hot water storage tank needs to be kept at 60 degrees or above to kill Legionella bacteria, which grow in warm, still water. A tempering valve then mixes the water down to 50 degrees before it reaches the bathroom.
Do I need a tempering valve on an instantaneous hot water system?
You generally do not need a tempering valve on an instantaneous or continuous flow hot water system that is preset to 50 degrees and feeds bathrooms, because it stores no water and never exceeds the bathroom limit. Units preset to 60 or 70 degrees, such as the Midea M20 70 degree model, do need one. Your licensed plumber confirms the requirement for your installation.
Can I set my hot water system to 50 degrees to save money?
You can set an instantaneous hot water system to 50 degrees or lower, but you should not set a storage hot water tank below 60 degrees, because a tank stored below 60 risks Legionella growth. Any energy saving from turning a tank down is small compared with the health risk.
What temperature is hot water in childcare and aged care in Australia?
Hot water in childcare centres, aged care, schools and hospitals in Australia is usually delivered at a maximum of 45 degrees at personal hygiene outlets, typically controlled by a thermostatic mixing valve. The exact requirement is set for each site by the plumber or hydraulic designer.
Get the right temperature model first time
Tell us which outlets the heater will feed and whether it is a home or a business. We will tell you whether a 50 degree model does the job or whether you need a hotter unit and a tempering valve. Browse the full instant hot water systems range or the Stiebel Eltron electric range.
Ask us which temperature model suits your home →
This guide is general information for Australian households and is not a substitute for advice on your specific home and site. Temperature requirements are set by AS/NZS 3500.4 and by state and territory plumbing regulations, which vary and change over time. Burn times are approximate. Gas continuous flow units must be installed by a licensed gas fitter and plumber. Electric instantaneous units must be installed by a licensed electrician, and 3 phase units need a 3 phase supply. Tempering valves must be installed and set by a licensed plumber. Confirm the temperature setting, valve requirements and installation costs with us or your installer before you buy.