The Mixet company is no longer in business, but thousands of their shower valves are still in operation. When repairs are needed, it is a fairly easy and inexpensive job to replace the internal cartridge with one offered by an aftermarket manufacturer, designed to match the original part. Simply look for a replacement cartridge specified to fit the Mixet faucet model you own.
Signs that a Mixet cartridge is wearing out include:
- Stiff diverter: It becomes difficult to divert the temperature from hot to cold on the temperature control.
- Dripping: The valve is dripping or takes a lot of tightening to close the valve fully and stop dripping.
- Temperature imbalance: The hot and cold water are not balancing properly.
- Frequent repairs: The plastic handle has needed repeated adjustment or repairs.
Equipment / Tools
- Tongue-and-groove pliers
- Utility knife (as needed)
- Replacement cartridge for Mixet faucet
- Plumber's stem grease
- Tub and tile caulk
Turn off the Water and Drain the Pipes
Shut off the water to the shower at the nearest branch shutoff (if available) or use the home's main shutoff valve. Turn on a bathroom sink faucet all the way to relive pressure and drain remaining water from the pipes. Remove the new cartridge from its package.
Remove the Handle, Temperature Knob, and Escutcheon
Remove the screw in the center of the handle and then pull the handle straight out and off. Remove the temperature knob by partially unscrewing the screw in the top of the knob. You may need to shake it back and forth and side to side to loosen it for removal.
Loosen the setscrew holding the escutcheon plate, then pull the plate off. If the plate is sealed with caulk, cut through the caulk bead with a utility knife to release the plate.
Remove the Old Cartridge
Use tongue-and-groove pliers to loosen the mounting nut securing the faucet cartridge. Turn the nut counterclockwise until it comes all the way off. The cartridge will remain inside of the valve body after the nut is removed.
Grip the flat ridges of the cartridge with the pliers, then turn the cartridge side to side while pulling straight out to remove it from the faucet body.
Some Mixet models have a retaining clip that holds the cartridge in place in addition to the nut. Remove this clip with needle-nose pliers before pulling out the cartridge.
Install the New Cartridge
Apply a thin layer of plumber's stem grease to the O-rings on the new cartridge. Align the cartridge for the proper insertion. There is usually a red mark on the cartridge indicating which side is up. If your temperature knob was in the down position, put the cartridge in with the red mark facing up. However, if your temperature knob was in the up position, the red mark down should face down.
Push the cartridge all the way in. If necessary, wiggle it with pliers as you push it in. Make sure the two brass rings are correctly positioned inside the mounting nut, then reattach the nut to the faucet body. Tighten the mounting nut firmly, but periodically check to make sure the cartridge can still be rotated side-to-side. If the cartridge is too stiff you can loosen the nut a bit.
Install the Temperature Knob and Handle
Fit the escutcheon plate back into place (or install a new one if you have it). Install the temperature knob, making sure the little nipple is in the groove of the cartridge before you tighten the screw. Put the handle back in place and secure it with its screw. Turn on the water and test the faucet to make sure it works properly.
Dry the area thoroughly with a rag. Caulk around the rim of the escutcheon plate to create a watertight seal and prevent water from getting inside the wall cavity. Let the caulk dry for 24 hours before using the shower.
Did You Reverse the Temperature?
It's a common mistake to install a Mixet cartridge so that the temperature controls are reversed—so that the hot is to the right and the cold is to the left. But this is easy to correct. Remove the handle and temperature knobs again, and open the water flow with the handle. While water is flowing through the spout, spin the cartridge in place 180 degrees. Reinstall the temperature knob and handle.