PHAM NEWS | FEBRUARY 2026 20 Pipes, Fittings& Valves


TMVs – a closer look at their inner workings


Altecnic’s Ed Morris delves into the inner workings of the thermostatic mixing valve. While it may seem like a small and inconspicuous part, TMVs play a signifi cant role in maintaining safety, comfort and effi ciency.


to ensure safe and comfortable hand washing, shower and bath water temperatures, reducing the risk of scalding. The controlling element


A


of the TMV is a temperature sensor which is fully immersed in the mixed water outlet port. This expands or contracts to continually maintain the correct proportion of hot and cold water entering the valve. Let’s look in more detail how


each internal component works to ensure the TMV functions correctly.


Internal components 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 fl ow 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. It is important that strainers are cleaned during TMV servicing to prevent potential blockages from a build-up of debris. Information on the frequency of servicing can be found in the manufacturer’s instructions.


Check Valves: Inside the TMV, there are check valves on both the hot and cold water inlets. These valves allow water to fl ow in only one direction, preventing backfl ow and maintaining the integrity of the hot and cold water supplies. By ensuring that water fl ows only from the inlets towards the mixing chamber, check valves help to prevent


TMV blends cold water with hot water and maintains this at a set constant outlet temperature


 TMV mixes incoming 60°C hot water (red) and 10°C cold water (blue) via inlets, regulating fl ow through central valve to output safe 41°C mixed water (purple)


 CHECK VALVES on hot/cold inlets prevent backfl ow, ensuring one-way fl ow to mixing chamber and avoiding cross-contamination


cross-contamination between hot and cold water lines.


Flow Conveyor: The fl ow 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 fl ow conveyor and the ratio of hot to cold water fl ow determine the outlet temperature of the TMV.


Ed Morris Technical manager at Altecnic


Thermostat: At the heart of the TMV lies the thermostat, a temperature-sensitive element that regulates the fl ow of hot and cold water to maintain a constant outlet temperature. The thermostat reacts to changes


Mixing valve cut-away


in the outlet temperature by adjusting the position of the valve within the fl ow conveyor. 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, eff ectively lowering the temperature. Conversely, if the outlet temperature drops below the set point, the thermostat will increase the fl ow of hot water to raise the temperature.


Safety in numbers By combining these internal components, TMVs ensure that the water delivered to taps, showers, or other fi xtures remain at a safe and comfortable temperature, regardless of fl uctuations 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 exemplifi es a commitment to safety, comfort, and effi ciency.


Choice of models


Altecnic have various models of TMVs that have been specifi cally designed and manufactured to meet the requirements of domestic and commercial applications. The Series 5213 Merchant Mixing Valve, for example, has been approved to TMV2 and TMV3 standard, and is both Kiwa and WRAS Regulation 4 approved. The 5213 failsafe design shuts off the mixed


The FLOW CONVEYORmixes hot and cold water streams in a chamber to achieve the desired outlet temperature


BALL VALVE ISOLATION & STRAINER on TMV inlets enable isolation for safe maintenance and servicing


THERMOSTAT regulates hot/cold fl ow, adjusting valves to maintain constant outlet temperature


water fl ow automatically in the event of disruption in the hot or cold-water supply to the valve, making it particularly benefi cial for protecting vulnerable people from serious scalding injuries. ◼ phamnews.co.uk/226/26


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