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When you think about it, many of us really do take hot water for granted. We turn on our hot water tap and water at the correct temperature is released from the faucet almost every time and when it’s not, we are pretty annoyed about it… just think about when cold water comes out of the showerhead when you turn on the hot tap.

One of the little additions to ensure that the water being used in your home is at the correct temperature at all times is a tempering valve. If you haven’t heard of them before, or aren’t sure how they work, you are not alone! That is why our hot water experts have collected some information to help you out – if you have any questions, give Brisbane Plumbing and Drainage a call on 1300 616 203 and we would be happy to assist further.

What is a tempering valve on a hot water heater?

A tempering valve, otherwise known as hot water mixing valve or a hot water tempering valve, is either a 2-inlet or 3-inlet adjustable mixing valve which is activated by temperature. It regulates the temperature that hot water is released from outlets throughout your home, by mixing both hot and cold water together to achieve a particular temperature.

How does a tempering valve work?

The way that a tempering valve works is not as complex as it may appear. A tempering valve contains a temperature-sensitive element, whose job is to focus on adjusting the mix of hot/cold water depending on:

  • What the tempering valve adjustment is
  • What the water temperature is for any incoming water flow

The mixing valve is a sliding component that is contained within the tempering valve, ensuring the correct ratio of hot to cold water is being let through, and a tempering valve usually controls the temperature within ±3%. This video explains the workings of a tempering valve:

What temperature is a tempering valve normally set at?

In Queensland, hot water must be heated to a minimum of 60°C to prevent the growth of bacteria such as Legionella, and a tempering device ensures that hot water is delivered to taps at a maximum temperature of 50°C.

What are the different types of tempering valves?

There are four different types of hot water mixing valves:



  • High performing
  • Best for heat pump and solar hot water systems
  • Suited for heaters where the incoming hot water can be close to boiling


  • Suited to most gas hot water systems
  • Remember, 50°C factory models that are pre-set generally do not need a tempering valve


  • Suited to systems that are low-pressure gravity feed and/or large capacity

Why does your hot water heater need a tempering valve?

For two major reasons:

  • Safety: To ensure that the water coming out of your taps isn’t too hot, so it doesn’t cause injuries such as scalding
  • Regulations: To comply with the relevant Australian Standards (A3500) when it comes to water coming out of your household outlets

How long does a tempering valve last?

Tempering valve generally has a lifespan of 5-8 years. After this time, they will generally require replacing.

TMV vs Tempering Valve – what’s the difference?

‍Tempering valves and TMVs (thermostatic mixing valves) get mixed up regularly, and they do have some similarities due to the fact they both mix hot/cold water together, but the main differences between the two are :

  • To install a TMV, a plumber must have a TMV licence
  • TMVs respond quicker to temperature changes than tempering valves. Places like schools and hospitals must have TMVs only, due to this point
  • TMVs are more expensive than tempering valves, but last longer
  • TMVs are generally repaired, not replaced

Who decides what temperature the water in your hot water system needs to be?

Your local building codes and government are the bodies that determine the relevant water temperatures.

The tempering valve specialists in Brisbane

If you have any further questions regarding tempering valves or would like to arrange for one of our qualified Brisbane plumbers to check a tempering valve in your home, give Brisbane Plumbing and Drainage a call on 1300 616 203 and we can help. ‍


Queensland Government (Department of Housing and Public Works – Hot Water System Requirements): https://www.hpw.qld.gov.au/construction/Sustainability/SustainableHousingLaws/Pages/ElectricHotWaterSystemReplacement.aspx