How To Adjust A Thermostatic Mixing Valve (TMV)

What is a thermostatic mixing valve?

A thermostatic mixing valve, or TMV, is installed in the hot water feed pipework in commercial environments. The TMV blends the cold and hot water feeds to deliver water to the user at a warm but safe temperature. TMVs ensure the water leaving the hot tap isn’t so hot that it might scald or burn the end user.

How to adjust a thermostatic mixing valve

A TMV has three pipe attachments: one for the hot and cold feed coming into the TMV and a mixed, ‘warm’ feed leaving the TMV and feeding the tap. You will also see a cap sticking up from the small unit on the thermostatic mixing valve. Once you remove this cap, you’ll see a small Allen key opening that can be turned left or right. This is to adjust how warm or cold you would like to blend in the warm exit feed. 

After adjusting, you must run the hot tap and use a thermometer to measure the temperature of the water leaving the tap.

Where is the TMV located?

Typically, thermostatic mixing valves are located beneath the wash basin or within the vanity unit, adjacent to a shower, in a commercial setting. Some sophisticated taps and showers also feature thermostatic mixing valves integrated into the unit's body. In some scenarios, a thermostatic mixing valve may have been used to service more than one wash basin, in which case the TMV may not be directly beneath the hand wash area. If you are installing TMVs as part of a new refurbishment project, you can see our guide on how to install a TMV. 

What temperature should my hot water be?

Hot water must be stored at a minimum temperature of 60 °C to kill Legionella and other harmful bacteria. There will be a drop in temperature by the time it reaches the pipes and exits the tap, but ordinarily, we would expect this drop to be about 10 °C. The recommended temperature for hot water in a commercial setting is 50 °C, with healthcare settings typically set slightly higher at 55 °C.

A TMV will blend the hot and cold water to a safe 40-42 degrees and should be installed as close to the tap or shower outlet as possible to minimise any heat loss through the pipes.

If you would like further advice on thermostatic mixing valves or managing hot water supply, contact one of the Commercial Washrooms team on 01202 650900.