HOT WATER COMPLIANCE
Thermostatic mixing valve vs tempering valve: the difference
A tempering valve and a thermostatic mixing valve both keep delivered hot water at a safe temperature, but they are not the same device and they are not used in the same places. Here is the difference, plainly.
The shared job: delivered temperature
Both devices exist to stop scalding. Heated water is stored hot to keep it safe from bacteria, then a valve blends it down so what reaches the tap is no hotter than the limit set for that situation. Getting that delivered temperature right is the point of both.
The tempering valve
A tempering valve is the common residential device. It blends hot and cold to hold the outlet temperature near a set point, within a wider tolerance. It is mechanical, robust, and suited to ordinary homes where the standard delivery limit applies.
The thermostatic mixing valve (TMV)
A thermostatic mixing valve holds the delivered temperature far more tightly and reacts faster to changes in supply. That precision is why a TMV is required in higher-risk settings: places like healthcare, aged care, and early childhood, where the people using the water are most vulnerable to a scald and the temperature has to be controlled closely.
Which one, and the records
For a standard domestic job, a tempering valve is usually the device. For a setting with vulnerable occupants, a TMV is required and also carries an ongoing service and testing obligation that generates its own records. Match the device to the setting, not to habit. For the temperature rule itself, see the hot water temperature rules.
What to photograph
Capture the valve in place, its markings, and the setting, plus a delivered-temperature reading at the fixture at commissioning. Elemetric keeps that with the job record.
Common questions
Can I use a tempering valve instead of a TMV?
Not in settings that require a TMV. A tempering valve suits ordinary residential work; healthcare, aged care, and early-childhood settings require a thermostatic mixing valve, which controls temperature far more tightly and is tested on an ongoing basis.
Do TMVs need ongoing testing?
Yes. Thermostatic mixing valves carry a periodic service and test requirement, which generates records best kept against the install.
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Download on the App Store →General information for licensed tradespeople, not legal or regulatory advice. The licensed plumber remains solely responsible for compliance. Refer to the current AS/NZS 3500 standards and the Building and Plumbing Commission (formerly the VBA) for authoritative requirements.