How To Adjust A Thermostatic Mixing Valve

What is a thermostatic mixing valve?

A thermostatic mixing valve, or TMV, is a device fitted before hot taps in commercial environments. The TMV blends both the cold and hot feeds of water in order to deliver water to the user at a warm, but safe temperature. TMVs are there to ensure that the water leaving the hot tap isn’t going to be so hot that it might scold or burn the end user. 

Where is the TMV located?

Usually, thermostatic mixing valves are located beneath the wash basin or within the vanity unit. Some sophisticated taps also have thermostatic mixing valves integrated into the unit. In some scenarios, you may also find that a thermostatic mixing valve has 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 here. 

How to adjust a thermostatic mixing valve

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

After you have made an adjustment, you must then run the hot tap and use a thermometer to measure the temperature of the water leaving the tap. 

What temperature should my hot water be?

Hot water needs to be stored at a temperature of at least 60ºC in order to kill Legionella and other harmful bacteria. There is obviously going to be some drop in temperature of the water by the time it gets down the pipes and out of the tap, but ordinarily we would expect this drop to be about 10ºC. The advised temperature for hot water in a commercial setting is 50ºC, with healthcare settings sitting slightly higher at 55ºC.

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