Why there are two temperatures
Stored water has to be hot. The building regulator says Legionella growth is reduced significantly when water is held at 60°C and above, and that turning the tank down will promote it.
Water at the shower has to be safe. For bathroom fixtures used for personal hygiene, the National Construction Code caps delivery at 50°C. Kitchens and laundries sit outside that rule.
The cap drops to 45°C in the residential part of aged care buildings, patient care areas of health-care buildings, parts of early childhood centres and schools used by children, and facilities for people with a disability.
NCC 2025 also suggests a lower temperature be considered in a home where the occupants are older adults or young children. That's guidance, not a rule.
Which device meets which limit
| 50°C limit | 45°C limit | |
|---|---|---|
| Tempering valve | Allowed | Not allowed |
| Temperature limited heater | Allowed | Not allowed |
| Thermostatic mixing valve | Allowed | Allowed |
| Thermostatically controlled tap | Allowed | Allowed |
When the heater is replaced: state by state
| Temperature control device needed? | |
|---|---|
| NSW | Yes, whatever the heater's type or location, like-for-like included. Not when only a solar collection panel is replaced. |
| Victoria | Not confirmed. NCC 2022 had a Victorian like-for-like exemption, and NCC 2025 has no Victorian variation for heated water. Ask the plumber. |
| Queensland | Yes. A temperature control device must be fitted to all new and replacement systems. |
| South Australia | Only where one was already in place, except solar: every new or replacement solar water heater needs one. |
| Western Australia | Yes, when a heater is replaced or relocated, except at basins in most building classes, houses included. |
| Tasmania | Yes, except for a single storage unit within a bank of heaters. |
| ACT | Not confirmed. NCC 2025 commenced on 1 May 2026 but isn't mandatory until 1 May 2027. |
| Northern Territory | Not confirmed. Ask the plumber. |
What the national code says
NCC 2025 requires a temperature control device when a hot water heater is replaced, regardless of its type or location. The only exemption is replacing some, but not all, of the heaters in a bank.
NCC 2022 was softer: a heater could be replaced in the same spot without one if the original installation didn't need it. Each state applies these with its own variations, which is why the table above differs. Victoria's Plumbing Regulations 2018 moved to a new version on 1 May 2026, and we haven't been able to confirm what that means for replacements there.
Fitting or swapping a valve is plumbing work. Ask for the plumber's licence number and check it: our licence guide shows where.
Signs the valve needs a plumber
- Bathroom water that runs hotter than it used to.
- Showers that swing between hot and cold.
- Water dripping from the valve body.
- Weak hot flow at the bathroom taps but not at the kitchen.
- A new system went in and nobody mentioned temperature control.
What a plumber will do
A plumber will measure the temperature at the bathroom outlets, then service, adjust or replace the valve, and note the setting. On a replacement heater, they'll tell you whether your state requires a device for that job and fit the right type.
Your checks, their adjustments
You can
- Notice when the shower temperature changed, and tell the plumber.
- Look for the valve on the hot pipe near the heater, so you can point it out.
- Leave the tank at its storage setting.
- Ask about a lower delivery temperature if young children or older people live with you.
Leave to a licensed plumber
- Adjusting, servicing or replacing the valve.
- Changing the tank thermostat. In Queensland, Queensland Health says a licensed electrician should do it.
- Repairing a thermostatic mixing tap. In Western Australia, it's left off the list of tap repairs homeowners may do.
- Fitting a valve as part of a replacement.
Questions to ask
- Is a temperature control device required for this job in our state?
- Which device will you fit, and where?
- What temperature will it deliver to the bathroom?
- How will I know when it needs servicing?
- Will it be on the compliance paperwork?
What we would do
Never fix a scalding shower by turning the tank down: you swap a burn risk for a Legionella one. Get a plumber who specialises in hot water to check or fit the right valve and set it. If you're replacing the heater, ask them to tell you in writing whether your state requires a temperature control device for the job.