Thermostatic Mixing Valve

A thermostatic mixing valve installs in-line between the hot and cold supply lines and a fixture, blending the two inputs to a consistent output temperature that doesn't drift when water is drawn elsewhere in the house — the classic scenario of a shower going suddenly cold when a toilet flushes elsewhere is exactly what this valve is designed to prevent.

The internal thermostatic element expands and contracts with temperature changes, automatically adjusting the hot/cold blend ratio to hold the output steady even as supply pressure or temperature fluctuates on either the hot or cold side. This is a mechanical, self-regulating process — no electronics or power source involved.

The valve body is brass, threaded for standard 1/2-inch supply line connections, and the output temperature is adjustable via a set screw during installation so it can be dialed to the desired setting once rather than needing readjustment at the fixture itself.