Altecnic: Inside a Thermostatic Mixing Valve (TMV)

Ed Morris, Technical Manager at Altecnic, delves into the inner workings of a crucial component in plumbing systems – the thermostatic mixing valve (TMV). While it may seem like a small and inconspicuous part, TMVs play a significant role in maintaining safety, comfort, and efficiency in various settings, from domestic systems to commercial buildings.

What is a TMV?
A Thermostatic Mixing valve blends cold water with hot water and maintains this at a set constant outlet temperature to ensure safe and comfortable hand washing, shower and bath water temperatures, reducing the risk of scalding.

When a TMV is fitted in the domestic setting, this is in a bath or sink, the TMV uses its temperature sensor, which is fully immersed in the mixed water, to control the temperature. When this sensor expands or contracts, the correct proportion of both hot and cold water is maintained in the valve.

Internal Components of a TMV

Ball Valve Isolation & Strainer:

A TMV typically includes ball valve isolators on the hot and cold water inlets. These valves allow for easy maintenance and servicing by enabling the isolation of the TMV from the rest of the plumbing system. When closed, they stop the flow of water into the TMV, ensuring safe access for maintenance or repair work.

Before water enters the TMV, it passes through a strainer. The strainer removes any debris or particles present in the water, preventing them from entering and potentially damaging the internal components of the valve. This helps to ensure the longevity and proper functioning of the TMV.

Check Valves:

Inside the TMV, there are check valves on both the hot and cold water inlets. These valves allow water to flow in only one direction, preventing backflow and maintaining the integrity of the hot and cold water supplies. By ensuring that water flows only from the inlets towards the mixing chamber, check valves help to prevent cross-contamination between hot and cold water lines.

Flow Conveyor:

The flow conveyor is a component responsible for mixing the hot and cold water streams to achieve the desired outlet temperature. It consists of a chamber where the hot and cold water streams meet and mix together. The size of the flow conveyor and the ratio of hot to cold water flow determine the outlet temperature of the TMV.


At the heart of the TMV lies the thermostat, a temperature-sensitive element that regulates the flow of hot and cold water to maintain a constant outlet temperature. The thermostat reacts to changes in the outlet temperature by adjusting the position of the valve within the flow convector. For example, if the outlet temperature rises above the set point, the thermostat will adjust the valve to allow more cold water into the mix, effectively lowering the temperature. Conversely, if the outlet temperature drops below the set point, the thermostat will increase the flow of hot water to raise the temperature.

By combining these internal components, TMVs ensure that the water delivered to taps, showers, or other fixtures remain at a safe and comfortable temperature, regardless of fluctuations in the incoming hot and cold water supplies. This not only enhances user comfort but also helps to prevent scalding injuries, making TMVs a crucial component in any plumbing system, especially in environments where vulnerable individuals, such as children or the elderly, are present.

As plumbing standards continue to evolve and safety regulations become increasingly stringent, the importance of TMVs cannot be overstated. Whether in residential homes, healthcare facilities, or commercial buildings, the inclusion of TMVs in plumbing systems exemplifies a commitment to safety, comfort, and efficiency.

Altecnic have various models of TMVs that have been specifically designed and manufactured to meet the requirements of domestic and commercial applications. The Series 5213 Merchant Mixing Valve, for example, has been approved to TMV 2 and TMV3 standard. The 5213 failsafe design shuts off the mixed water flow automatically in the event of disruption in the hot or cold-water supply to the valve, making it particularly beneficial for protecting vulnerable people from serious scalding injuries.

The Mixcal Careflo Plus® TMV from Altecnic also meets the requirements of BS 7942:2000 and the NHS model engineering specification D08 for use in healthcare settings, hospitals, care homes and schools. The TMV has all the functions of a conventional TMV, such as blending hot and cold water and a failsafe function and is also equipped with a unique thermal override function to allow for thermal disinfection right to the outlet.

For more information on Altecnic’s TMV range, visit www.altecnic.co.uk or head to stand 5E30 at InstallerSHOW.
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