Grohe manufactures several signature lines of faucets for high end homes and residential properties. Grohe faucets rely on a replaceable cartridge system that you must replace every three to five years or as needed. The Grohe cartridge controls water pressure for the faucet as well as the mixture of hot and cold water. As the faucet cartridge ages and builds up with lime and other minerals, the faucet may leak or start dripping while the faucet is in the "off"position.
Shut the handles for the water main off. Locate the handles (either one or two) connecting to rigid copper piping or flexible metal tubing, and turn these (left) counterclockwise 1/4 turn to reach the "off"position. The water main is located underneath the cabinets of the room you are working in. (See Warnings.)
Insert the allen wrench into the star-shaped aperture located beneath the Grohe faucet spigot. Turn the wrench counterclockwise until the handle comes off fthe spigot (4 to 6 rotations).
Remove the faucet handle from the assembly. This will allow you to access the cartridge system located directly beneath the handle.
Grasp the cartridge firmly with your pliers, turning it counterclockwise until you hear a clicking sound, signaling that you have unlocked it from the cartridge assembly.
Remove the cartridge. You may need to use the pliers for leverage to remove the cartridge. (See Tips.)
Insert the new cartridge into the assembly, using your pliers to turn the cartridge 1/4 turn clockwise, locking it into place.
Reattach the Grohe faucet handle, using the allen wrench (clockwise) to tighten it into place. Make sure it is as tight as you can make it by hand without stripping it or using a tool, which may damage the faucet.