Hot Water Mixing Valve - Hot Water Tempering Valve Adjustment - Hot Water System Installation Regulations - Tempering Valve Regulations
A hot water tempering valve is a temperature activated 3-way mixing valve used to temper a hot water supply by mixing in cold water with the hot water, delivering reduced temperature water, decreased scalding risk and improved safety.
A tempering valve is an adjustable 2-inlet mixing valve which is temperature activated and used to moderate a hot water flow by mixing the hot water with cold water to achieve ≅50°C (122°F). This reduced temperature water is then delivered to the taps and shower heads around your home. The temperature delivered is set by local building codes.
A hot water mixing valve or tempering valve keeps the tank hot enough to stop bacterial growth (>60°C) and provides a lower hot water tap temperature (≅50°C) to help reduce the risk of accidental scalding.
The hot water system installation regulations include tempering valve regulations that now require hot water tempering valves, to protect against scalding. Your plumber will make a hot water tempering valve adjustment to make sure your tap temperature does not exceed 50°C.
A hot water mixing valve or hot water tempering valve is a safety device that mixes cold water with the hot water, to help prevent scalding. Hot water tempering valve adjustment is done to comply with tempering valve regulations.
Hot water tempering valve regulations require reducing the heat of the hot water to a maximum tap temperature (usually 50°C) for improved safety.
Hot Water Mixing Valve for Scalding Hazard Prevention
Scalding is one of the most serious, painful and long-term injuries for young children. Scalding can happen very quickly, depending on the temperature of the water.
However, with the hot water from tap temperature at 50°C a serious burn wouldn’t typically happen until after 5 minutes, so you can see the benefit of hot water mixing valve in controlling the hot water tap temperature.
Hot Water Mixing Valve Explained - Tempering Valve Regulations Compliance
A hot water mixing valve maintains a high tank temperature whilst simultaneously providing more tepid water for taps, with the temperatures specified by tempering valve regulations. This keeps the tank hot enough to stop bacterial growth (>60°C) and provide a lower hot water from tap temperature (≅50°C) to help reduce the risk of accidental scalding.
A hot water mixing valve works by mixing in cold water with your hot water, before it reaches your taps.
Hot Water Mixing Valve - Tempering Valve: How it Works
A hot water mixing valve or tempering valve works with a temperature sensitive element which adjusts the mix depending on the hot water tempering valve adjustment and the temperature of the incoming water flowing through the valve. The hot water mixing valve mechanism is a sliding valve within the tempering valve that works to vary the ratio of hot and cold water that is allowed to pass. The tempering valve works to control the temperature, typically to within ±3%.
Your plumber sets the hot water tank temperature control to the reach the minimum required 60°C, per the tempering valve regulations. Then your plumber makes the hot water tempering valve adjustment on the hot water mixing valve to not exceed the maximum hot water from tap temperature of 45°C or 50°C.
The hot water mixing valve (tempering valve) works to reduce the hot water demand on the tank. You decrease your hot water usage by mixing cold with hot water.
This video shows how a hot water mixing valve or tempering valve works (there is no audio):
Hot Water System Installation Regulations - Tempering Valve Regulations - Conflicting Requirements
Hot water temperature in Australia, governed by hot water system installation regulations, including tempering valve regulations, is for a minimum of 60°C in a hot water tank and the maximum hot water from tap temperature of 50°C at any personal hygiene tap or showerhead. The maximum hot water from tap temperature is 45°C for hospitals, schools, nursing homes and similar facilities, based on the tempering valve regulations.
The hot water mixing valve must help meet these different goals. The goals require the hot water mixing valve to prevent scalding and dangerous bacteria growth.
The tempering valve regulations come from the Plumbing Code of Australia (PCA), which has two conflicting requirements.
To protect against the growth of Legionella bacteria, the cause of Legionnaires’ disease, it is a legal requirement that the hot water tank temperature adjustment be set at a minimum temperature of 60°C.
However, at 60°C a serious burn can occur in 1 second.
This requirement is as per Australian Standard AS3500.4.2 Clause 1.6.
This applies to all hot water systems with tanks, including solar and heat pumps.
On the other hand, the Code requires that the hot water from tap temperature for personal hygiene purposes (primarily bathroom taps) is not to exceed 50°C.
The maximum hot water from tap temperature is 45°C for early childhood centres, primary and secondary schools, and nursing homes or similar facilities for young, aged, sick or disabled persons.
So, how are both of these requirements met?
Hot Water Mixing Valve Now Required by Hot Water System Installation Regulations
The hot water system installation regulations now requires that hot water mixing valve reduce the hot water from tap temperature to 50°C in bathrooms.
Kitchen and laundry applications are still permitted to bypass the hot water mixing valve and use the hot water directly from a standard electric or gas hot water tank.
Please see the hot water mixing valve flow chart below.
Thermostatic mixing valves are required for the previously mentioned facilities that require a hot water from tap temperature of 45°C.
Thermostatic mixing valves are faster in responding to temperature and pressure changes and typically limit output temperature variances to ±1%.
The exceptions to this rule are tankless continuous flow hot water systems. These are LPG or natural gas powered.
As they have no tank in which Legionella bacteria can breed, they do not have to be set at 60°C.
Typically, they are factory pre-set to 50°C. As a result, no hot water mixing valve is required.
Tempering Valve Adjustment - Hot Water Tempering Valve Adjustment
Let the water run for a minimum of one minute to make sure the input water temperatures have stabilised after the tempering valve adjustment. To adjust temperature, you must remove the protective cap to access the adjustment knob.
Before any hot water tempering temperature adjustment, you plumber will first check to make sure that the tank temperature is set to at least the required minimum of 60°C.
When performing a hot water tempering valve adjustment (tempering valve adjustment), the tap tested should always be the one closest to the hot water source and the hot water flow rate should be at least 4L/min (1 gallon/min). The plumber will turn the knob on the hot water tempering valve adjustment to mix in the cold water with the hot water, until the required hot water tap temperature of 50°C (or as required) is achieved (temperature valve for hot water).
Hot water tempering valve adjustment should only be done by your plumber. It should not be attempted by the homeowner.
Types of Hot Water Mixing Valve
There are different types of hot water mixing valve or hot water tempering valve for hot water temperature control of different types of hot water heaters.
This is the most common type of hot water mixing valve and is used with electric water heaters that typically supply hot water between 65°C and 75°C.
This hot water mixing valve is designed for most types of gas hot water systems, including gas storage and tankless continuous flow models.
This high performing hot water mixing valve is for use with solar hot water and heat pump hot water systems, where the incoming hot water temperature can approach boiling point.
Tankless Continuous Flow Hot Water
Traditional Hot Water Tanks
When it's time to get a new hot water system, two of the most asked questions are:
1. “Should I get a traditional hot water tank or a tankless continuous flow system?”
2. "What size hot water system do I need?"
We review the two hot water system types and compare the pros and cons of both, as well as the prices, to help you make an informed decision.
We also explain hot water heater sizing.
Both types of heaters supply hot water but they do it in different ways.
Let’s look specifically at the points of difference:
Running Out of Hot Water
Traditional hot water tank heaters can only heat a certain number of litres at a time.
Residential hot water heaters are typically in the 135L to 170L range.
Off-peak electric units need to have a much larger capacity, as they have to last through the entire day.
Once all of the hot water in the tank is used up, it takes time to heat up the fresh water entering the tank.
If it runs out right in the middle of a shower, you have an uncomfortable problem.
You can finish with a cold shower or just stay soapy while you wait for the water to reheat.
Neither is a good choice.
With a tankless continuous flow hot water system, the water is heated as you use it.
The unit can maintain the flow rate indefinitely.
So, you basically never run out of hot water, no matter how many people get to the shower before you.
Tankless gas hot water systems only needs to run when the hot water is actually required and wasteful pilot lights are a thing of the past.
On the other hand, with a hot water tank, you have to use energy to maintain the temperature of the stored water 24/7.
The technology and energy saving designs are also very different.
Modern tankless continuous flow models typically have a 6 Star energy rating.
There are even 7 Star units now available.
Tankless systems are available in both natural gas and LPG models.
In contrast, most tank hot water heaters are only rated at 4 or 5 Stars.
This means both the energy consumption and the running costs will be higher.
Tank heaters are available in electric, natural gas and LPG models.
So, while we'd love to sell you more gas, we'd rather have you saving money and energy with the more efficient models.
They are also the best choice for the environment.
Size and Aesthetics
Storage tank hot water heaters are big, especially the electric off-peak models.
Even when installed outdoors, the size can get in the way, particularly with today’s smaller lot sizes.
Having this large object next to your house also does nothing for the appearance of your home.
At about the size of a small suitcase, tankless water heaters are much smaller than a traditional storage tank heater.
Mounted flush against the wall, the smaller tankless units take up less space and are also more aesthetically pleasing, as they don’t dominate the exterior appearance of your home.
Greenhouse gas emissions are reduced through the use of tankless water heaters.
Tankless gas hot water systems produce about 75% less CO2 greenhouse gas emissions, when compared to a storage tank hot water systems powered by coal-fired electricity.
Even when compared to gas storage tank units, tankless units are more eco-friendly.
The 6 to 7 Star tankless models consume less gas and create less CO2.
Traditional storage tank water heaters have a life span of around 10 to 12 years.
Warranties for storage tank units are typically 5 to 10 years.
Tankless hot water systems can last up to 20 years.
Warranties for tankless units are typically 10 to 12 years.
Water from a storage tank water heater may pick up bits of rust and scale that build up within the tank.
Since there's no tank to rust and no water stored with a tankless system, the water stays cleaner and fresher.
When you first turn on the tap, there is typically a delay in getting hot water, as the water in the pipes leading from the water heater to the tap will be cold.
Because it is kept hot, tank systems can be slightly faster in delivering the initial flow of hot water, as the tankless system takes a second or two for the unit to get up to temperature.
However, now there is a new system to eliminate the delay entirely.
The Rinnai Smartstart® Water Saver was developed to reduce water wastage whenever a hot water is turned on. It pre-heats the water in the pipes before you turn on the hot tap.
It is part of the Rinnai Infinity range of tankless systems.
In the past, there was a substantial difference in the price between tankless and storage tank hot water units.
However, the days of super cheap 3 Star storage tank units are long gone.
The difference has now shrunken to the point where there is almost price parity between comparably sized units.
This is especially true if you are comparing 5 Star tank units to the 6 or 7 Star tankless models.
Health & Safety
With storage tank water heaters, there is the potential for bacteria growth within the tank.
The World Health Organisation -- WHO -- recommends that stored hot water be kept at a minimum of 60°C.
Unless a minimum of 60°C is maintained, hot water tanks can be a breeding ground for Legionnaires’ disease, or Legionellosis, that is caused by a bacterium, Legionella pneumophila. It is a respiratory disease that can cause severe pneumonia and is sometimes fatal.
However, Canadian studies have shown, even when the thermostat is set at 60°C, a high percentage -- approximately 40% -- of electric water heaters remain contaminated.
This is because of the lower temperature, of about 30°C to 40°C, at the bottom of the tank.
With tankless systems, the prevention of bacterial growth is not an issue, as there is no stored water in which bacteria can breed.
Tankless systems can also be set at 50ºC, so the risk of scalding is greatly reduced without the need of a tempering valve.
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The information in this article is derived from various sources and is believed to be correct at the time of publication. However, the information may not be error free and may not be applicable in all circumstances