See our animation of a working TMV. Using the diagram opposite to identify the active components, click the appropriate link below to view the animation.

The animation shows a HORNE thermostatic mixing valve (TMV) in section. The internal mechanism is revealed showing the flow paths of hot and cold water supplies entering the TMV and mixing around the thermostat element before passing to the outlet.

Changes in the hot or cold water supply pressures or temperatures will result in expansion or contraction of the thermostat element which, in turn, creates movement of the slide valve. The movement of the slide valve between the hot and cold faces will simultaneously alter the proportion of hot and cold water entering the TMV, thus maintaining the mixed water temperature.

A cold water supply failure shows how the thermostat element will rapidly expand to move the slide valve to close on the hot face thereby closing off the hot water supply to the outlet.

All Horne TMVs, the Optitherm thermostatic tap and the TSV1 shower valve operate on this principle.