Why Do I Need A TMV or Tempering Valve? 1

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Why Do I Need A TMV or Tempering Valve? 2

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Every week we have clients asking why we are required to install a TMV or tempering valve to their hot water system. The short, simple answer is because it’s the law.

The longer answer is because it’s about safety. A TMV or tempering valve reduces the risk of scalding. This is because storage type gas, electric, solar and heat pump systems are storing hot water at between 60° C and 75° C. You need to be aware a severe hot water burn can occur in one second when the water is delivered at 60° C or higher. Hot water burns like fire because:

  • At 60°C, a severe burn can happen in 1 second
  • At 55°C, a severe burn would take 10 seconds
  • At 50°C, a severe burn would happen after 5 minutes

What is a TMV?

TMV or thermostatic mixing valve installed by Whywait Plumbing Services Gold Coast

TMV or thermostatic mixing valve installed by Whywait Plumbing

A TMV is a thermostatic mixing valve but is commonly referred to as a TMV. The role of a TMV is to mix hot and cold water together to provide you with hot water delivery at your tap that is at a consistent temperature.

When we install your TMV, we set the temperature to deliver the hot water in all bathrooms at 45°C in aged care or childcare facilities or 50°C in all other bathrooms.

A TMV is compulsory for use when used in common areas for aged care or childcare. A TMV is very accurate and very responsive to fluctuations in incoming water temperatures keeping the temperature to within 1° C of the temperature that it has been set at when we install it.

Accuracy of temperature in the TMV is delivered by a thermally sensitive element which expands and contracts in response to the temperature fluctuations of the incoming cold and hot water. This expansion and contraction regulate the temperature by controlling how much cold water mixes with the hot water. An added safety feature of a TMV is that if cold water flows become too low, they shut down to prevent 60°C plus water being delivered.

What is a Tempering Valve?

illegal tempering valve installation replaced by Whywait Plumbing

Non-compliant tempering valve installation connected with flexihoses replaced by Whywait Plumbing

A tempering valve’s role is also to mix hot and cold water together to provide you with hot water delivery at your tap that is at a consistent temperature.

The tempering valve is a simple three-way valve that is temperature actuated to mix the hot and cold water. These days most come preset at 50°C and when we install them, we test them by measuring the temperature of the water from your hot taps in the bathroom.

A tempering valve is commonly used in residential homes as a one-off valve at the hot water service. A tempering valve is slower to respond to temperature fluctuations compared to a TMV plus it will deliver water to within 3°C of the temperature that it has been set at when we install it.

Which Valve do you Require?

The Plumbing Code of Australia in AS/NZS 3500.4:2018 is very specific about water temperature is section 1.11, which states:

  • To avoid the likelihood of legionella bacteria growth, an installation shall store water at a temperature of not less than 60°C
  • All new heated water installations shall deliver heated water not exceeding 45°C for the aged, the sick, children or people with disabilities in healthcare, aged care, early childhood, schools and nursing homes. For all other situations, heated water shall be delivered not exceeding 50°C.

Ultimately when we are installing a temperature control device, we are legally obliged to comply with the requirements above and much more as they are prescribed in AS/NZS 3500.4:2018.

Overall a TMV is more expensive to install initially compared to a tempering valve. However, a TMV has a much longer working life span compared to a tempering valve as they are more accessible to service and replace the working parts. A tempering valve, by comparison, is usually just replaced when it stops working as they are not easy to service or replace parts in.

In Queensland, all work undertaken on a TMV or tempering valve is reportable to the QBCC and must have a compliant Form 4 submitted. For your protection always demand a copy of your Form 4.

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