Plumbing – this plumbing “temperature regulator” called, and how to adjust it


I was told the below restricts/governs how much hot water can make it to my tub/shower. I'd like to know what it's called, and how I can adjust it to get hotter water.

enter image description here

I'm attempting to twist the "cap" (the beige-ish color) to the right, but am meeting more resistance than I would have expected (having no knowledge of how it works). I'm afraid to attempt to turn too hard for fear that it is not what I'm supposed to adjust, and I could break/crack the pipe.

Or do I need to find an alan wrench or similar to adjust just the little silver deal at the top?

Best Answer

Thermostatic Mixing Valve

According to the installation instructions (PDF)

enter image description here

  1. Let the water flow for at least two minutes to allow supply temperature to stabilize.
  2. Calibrate the mixed water outlet temperature by placing a thermometer in the mixed water stream.
  3. To adjust the setting of the valve, loosen locking cap screw with hex wrench, see Figure 4. Cap must be lifted 1/4" to adjust temperature. To increase the temperature, turn counter clockwise. To decrease temperature turn clockwise.
  4. Lower handle and tighten screw.
  5. Check outlet temperature.