What is a Hot Water Tempering Valve?

A hot water tempering valve is a safety device that controls the temperature of hot water delivered to fixtures like taps and showers. It mixes cold water with hot water to achieve a predetermined temperature, preventing scalding and ensuring comfortable hot water use. It is typically installed on the hot water line, between the hot water heater and the point where hot water enters the home’s plumbing system. It acts as a safety buffer, controlling the maximum hot water temperature before it reaches fixtures.

Hot water tempering valves offer numerous benefits, including:

• Safety: Temperatures exceeding 50 degrees Celsius can cause severe burns. A tempering valve prevents scalding by limiting the maximum hot water temperature.
• Comfort: Temperatures fluctuate naturally in hot water systems. A tempering valve maintains a consistent temperature, ensuring comfortable hot water.
• Energy Savings: Temperatures above 50 degrees Celsius are inefficient and waste energy. A tempering valve reduces energy consumption by limiting the maximum hot water temperature.
• Reduced Bacteria Growth: Hot water storage tanks are often set to 60°C+ to prevent the growth of bacteria like Legionella as per the requirements of the Plumbing Code of Australia 2011 (Volume Three). However, this temperature is too high for safe use. Tempering valves mix hot water with cold, reducing the temperature to a safe 50°C, thus lowering the risk of bacterial growth and associated illnesses like Legionnaires disease.

Pressure-balanced tempering valves rely on a pressure-balancing mechanism to maintain a constant temperature, regardless of pressure fluctuations in the water supply. They typically use a diaphragm or piston to regulate the flow of hot and cold water, ensuring a consistent temperature output even if pressure changes occur. Pressure-balanced valves are generally simple and reliable, making them a popular choice for residential applications.

Thermostatic tempering valves use a thermostat to control the temperature of the mixed water. The thermostat senses the temperature of the mixed water and adjusts the flow of hot and cold water to maintain the desired temperature. These valves offer precise temperature control and are often used in applications where consistent temperature is critical, such as commercial buildings and healthcare facilities. However, their more complex design can make them more expensive than pressure-balanced valves.

Electronically controlled tempering valves utilise an electronic controller to monitor and adjust the water temperature. They typically include sensors to detect the temperature of the mixed water and an electronic controller to adjust the flow of hot and cold water to maintain the desired temperature. Electronic tempering valves offer the most precise temperature control and can integrate with building automation systems, allowing for remote monitoring and control. They are often used in large commercial buildings and industrial facilities where sophisticated temperature control is required.

Choosing the right tempering valve depends on several factors that align with your specific needs and application:

• Flow Rate Requirements: The valve’s capacity, measured in gallons per minute (GPM) or litres per minute (LPM), should match the size of your hot water system and plumbing system’s flow rate to ensure adequate hot water supply. A valve that is too small will restrict flow, while a valve that is too large may not be able to accurately control the temperature.
• Temperature Control Range: The valve’s temperature control range should accommodate the specific temperature needs of your application. Consider the desired temperature setpoint and the acceptable variation in temperature.
• Installation Considerations: Assess the valve’s compatibility with existing plumbing, including pipe size, pressure rating, and connection types. Check for compatibility with existing valves and fittings to ensure a seamless installation.
• Budget: Prices vary among brands and models, ranging from basic pressure-balanced valves to more advanced electronically controlled options. Consider the features and benefits offered by each type and determine the best value for your needs and budget.

The terms “hot water tempering valve” and “thermostatic mixing valve (TMV)” are often used interchangeably, but there’s a subtle difference. A hot water tempering valve is a general term for any valve that controls and limits the temperature of hot water delivered to fixtures. This category includes various valve types with different mechanisms. A thermostatic mixing valve (TMV) is a specific type of tempering valve that uses a thermostat to regulate the temperature of the mixed water. Essentially, all TMVs are tempering valves, but not all tempering valves are TMVs. In practical terms, the difference isn’t always significant. Both types perform the primary function of controlling hot water temperature to prevent scalding and ensure safety. However, specific features and capabilities may vary between different types of tempering valves.

No, a tempering valve can only be changed by a licensed plumber. Tempering valves are essential for hot water safety, and incorrect installation can lead to serious consequences like scalding, leaks, and damage to your plumbing system.

Replacing a tempering valve is a complex task requiring a licensed plumber with expertise in plumbing systems, proper tools, and a thorough understanding of local building codes and regulations. The installation must comply with Australian Standards AS/NZS 3500 and relevant Codes of Practice.

Legally, a tempering valve cannot be set above 50 degrees Celsius to ensure safety. However, if you need to reduce the temperature to protect people in your home or business, a plumber can adjust the valve to a lower temperature, typically between 35 to 50 degrees Celsius. Remember, a minimum 10°C temperature differential is required between the hot water inlet and the mixed water outlet to guarantee proper operation of the thermal shut-off feature, further emphasising the importance of professional installation.

When a tempering valve fails, it can seriously affect safety and comfort. Here are some potential outcomes:

• Scalding: The primary purpose of a tempering valve is to prevent scalding by controlling hot water temperature. If it fails, hot water could reach dangerous temperatures, posing a risk of severe burns.
• Inconsistent Water Temperature: A faulty tempering valve might deliver inconsistent water temperatures; sometimes, the water will only be warm, sometimes there will be no hot water at all, causing discomfort and making it difficult to maintain the desired temperature in showers or baths.
• Water Waste: A malfunctioning valve could lead to excessive water use as it struggles to regulate temperature. This can result in wasted water and higher water bills.
• Plumbing System Damage: A failing valve could lead to leaks, which can damage surrounding structures and cause water damage.
• Increased Energy Costs: Inconsistent temperature control can lead to inefficient energy use as the hot water heater cycles on and off more frequently.

It’s essential to address any signs of a failing tempering valve promptly. If you suspect a problem, contact a licensed plumber for inspection and repair.

There’s no set timeframe for replacing a tempering valve. Its lifespan depends on various factors, including:

• Usage: Frequent use and high water pressure can accelerate wear and tear.
• Water Quality: Hard water containing minerals can lead to mineral build-up and affect valve performance.
• Maintenance: Regular maintenance, like cleaning and inspection, can extend the valve’s life.
• Installation Quality: Proper installation by a licensed plumber contributes to a longer lifespan.

Generally, a tempering valve can last 10-15 years with proper maintenance. However, it’s essential to watch for signs of failure, like:

• Inconsistent Temperature: Noticeable fluctuations in hot water temperature.
• Leaking: Water dripping from the valve or connection points.
• Noisy Operation: Unusual sounds like rattling or grinding.
• Reduced Flow: A decrease in water pressure.

If you notice these signs, contact a licensed plumber for inspection and potential replacement. They can assess the valve’s condition and recommend the best course of action.