What is a Thermal Mixing Valve (TMV) and how does it work?

TMV stands for Thermostatic Mixer Valve, a fitting installed to control the temperature of water coming from a tap or showerhead. It’s an essential component of plumbing installation in a commercial washroom setting that protects users from scalding. 

In all buildings, particularly large locations like hospitals and schools, it can be challenging to maintain a consistent water temperature from one end of the property to the other. By fitting thermostatic mixer valves, the flow of water is regulated to a safe temperature throughout the site. 

The difference between mixer taps and mixer valves

You may have heard the term 'mixer tap' before, which refers to a single tap that provides both hot and cold water. Often, this tap will have a control that allows you to slide the opening between hot and cold water. However, you should not confuse a TMV with a mixer tap. 

While a mixer tap or shower allows you to adjust the temperature of the water coming out of the tap, the TMV is directly responsible for the temperature of the hot water feed before it reaches the tap, regardless of whether it is a mixer or not.

How a Thermostatic Mixing Valve Works

A thermostatic mixer valve works by blending a mains hot and a mains cold feed into a single warm feed. In some cases, one TMV can be used to supply up to three or four outlets; however, it’s essential to note that the further an outlet is from the TMV, the lower the temperature will be.

A TMV can also immediately shut off the hot water flow through the valve if the cold supply ever fails. This is vital as it could save a user from being scalded.

TMV2 or TMV3?

There are two types of thermostatic mixer valves, TMV2 and TMV3. Your common TMV2 is the type of valve commonly used in domestic environments, although it is also sometimes used in small business settings. They work with water pressures from 0.1 to 5 bar.

TMV3 is a commercial-grade mixer valves that work with pressures up to 10 bar. These are specifically designed for commercial environments and are required in hospitals, schools, and healthcare settings. TMV3s are needed to adhere to NHS D08 regulations. While TMV2 still meets two main British standards, it can’t be used in healthcare settings. TMV3s are more robust and influential, making them essential for commercial-grade washrooms, showers, and changing rooms.

Our most popular thermostatic mixing valves are the Intamix and the Bristan Sirrus. Both are regulated to TMV3 standards. For installations with limited space, we recommend the Delabie Compact Nano TMV3 Thermal Mixing Valve.

If you would like more advice on which TMV you need for your washroom or to speak with a member of our team, please get in touch on 01202 650900.