Some Grohe shower faucets feature anti-scald technology, also known as a shower thermostat or a thermostatic mixer. These specialized shower valves not only limit the maximum water temperature that will exit the showerhead but also help keep your shower water at a consistent temperature. This prevents you from getting a surprising surge of hot or cold water when someone else turns on a faucet or the dishwasher kicks off.
Thermostatic valves need to be calibrated during installation for the best results. Fortunately, Grohe has made its anti-scald shower faucets user-friendly for easy adjustments after installation as well. You will need a thermometer and possibly a flat-head screwdriver.
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Adjusting GrohTherm 1000 Grohe Faucet
Grohe's thermostatic mixer shower faucets come in several different styles. One option — like the GrohTherm 1000 — is shaped like a horizontal bar or cylinder. Turning one handle toward you will increase the temperature, whereas the other handle controls the water volume. To start the adjustment procedure, turn the temperature handle so that the "38 degrees" label lines up with the dot on the other side.
Then turn the water on, and make sure the diverter is pushed down so that water flows through the faucet (remove the showerhead attachment if your model does not have a diverter). Allow the tip of the thermometer to sit in the stream of water until the line stops moving, taking care not to get your hands wet in the process just in case the water is too hot. If the thermometer indicates that the water is hotter than 38 degrees Celsius (or hotter than your preferred temperature), you'll need to adjust the thermostatic valve.
To access the adjustment mechanism, pull the end cap off the temperature handle and remove the screw with a flat-head screwdriver. Then pull off the decorative handle cover. Turn the water on again and keep the thermometer in the stream of water. Slowly rotate the black adjustment knob away from you until you're satisfied with the temperature, and then reinstall the faucet cap.
Adjusting GrohTherm SmartControl Thermostatic Valve
Many of Grohe's faucet trim sets feature the GrohTherm SmartControl design, which includes a series of push-button diverters and pressure valves plus a large central knob that controls the water temperature. If you're in the process of installing one of these styles, you can adjust the temperature before any of the decorative knobs or escutcheons are in place. You can also easily adjust the temperature at any time after installation.
With just the cartridge in place, push in one of the diverter buttons to turn on the water. Hold the tip of the thermometer in the stream of water until the line stops moving. If the temperature reading is too hot, turn the bottom stem to the right. If it's too cold, turn it to the left.
With the trim already fully installed, turn the temperature control all the way to the left and pull the cap off. Pull the gray plastic adjuster out slightly so that it is able to turn the inner mechanism but not the outer knob. Turn the water on, read the temperature, and turn the gray adjuster to the left for more heat or to the right for less heat. Pull the adjuster all the way out, reposition it so that the long, curved side is at the top and reinstall it by pushing it all the way in.