How do I calibrate the cartridge on a GROHE thermostatic shower valve?

To adjust the water temperature, access the regulating cap beneath the thermostatic handle. Rotate the cap until the water reaches 100°F, then reinstall the handle, aligning the 100° mark to the 12 o'clock position.

Grohtherm / Grohtemp Valve Calibration:

 

1. Access the Regulating Cap: Begin by removing the thermostatic handle.  This will reveal the regulating cap, which may be black or green, depending on your trim style.
   1. If using the 34331or 34397 valves, the cap will either be a white or brass spline.
2. Locate the Regulating Cap: Refer to the drawing below and identify the regulating cap marked "A".
3. Turn on the Water and Measure: Turn on the water supply to the valve and hold a thermometer under the stream.
4. Adjust the Temperature: Slowly rotate the regulating cap (marked "A") clockwise or counter-clockwise until the water temperature reaches and stabilizes at 100 degrees Fahrenheit.

    

5. Reinstall the Thermostatic Handle: Align the thermostatic handle to indicate 100° when positioned at the 12 o'clock mark and reinstall it securely.

Please note:

If your valve is only dispensing extremely hot or cold water, and no mixing is occurring, there may be an issue with the plumbing:

 

• Reversed Valve Installation: The valve itself might be installed upside down.
  
• Crossed Supply Lines: The hot and cold water supply lines may be connected to the wrong ports.  Ensure the hot water line is connected to the "H" or "W" port, and the cold water line is connected to the "C" or "K" port.

 

To resolve this issue, you can either:

• Re-pipe the Valve: Correct the plumbing by ensuring the valve is installed in the correct orientation and the supply lines are connected to the appropriate ports.
• Use a Reversing Cartridge: If re-piping is not feasible, a reversing cartridge can be installed within the valve to compensate for the incorrect plumbing.