Things You'll Need
Flat-bladed and Phillips-head screwdrivers
Moen bathroom faucet cartridge
Moen has been a manufacturer of bathroom and kitchen faucets for more than 50 years. They pioneered the familiar single-handled faucet so prevalent in kitchens and bathrooms. But no matter which Moen faucet you use, they all have one thing in common: the Moen 1225 cartridge. This cartridge works by helping to regulate the water temperature and pressure, so you always get what you want when you turn on the faucet. Occasionally these cartridges wear out and stop working. If you notice that the water pressure in your bathroom sink is below par, it's time to replace the faucet cartridge.
Turn off the water supply to the bathroom faucet you will replacing. The shutoff valves are usually located beneath the sink. Turn the knobs clockwise to shut off the water. Open up the faucet and allow any water present to drain out.
Remove the Moen bathroom faucet cover. Use the flat-bladed screwdriver to gently pry off the top of the faucet.
Unscrew the faucet screw with (in most Moen models) a Phillips-head screwdriver. Pull up on the faucet head to remove it from the cartridge body.
Use an adjustable wrench to unscrew the container nut that holds the Moen faucet cartridge in place. Lift it up and out of the faucet body. Use a pair of pliers if the cartridge is difficult to remove.
Insert the new faucet cartridge into the opening. Thread the cartridge retainer nut back on the cartridge and tighten in place with the adjustable wrench.
Place the faucet handle back on top of the cartridge. Secure in place with the screw.
Replace the faucet cap. Tap it in gently with the base of the screwdriver to secure in place.
Moen makes a special cartridge remover tool that you can use if you find it hard to remove the cartridges. Check on the Moen website or at a nearby plumbing store to see whether they have any in stock.
The above steps are just a guideline. Always follow the instructions for replacing the faucet cartridge for your particular Moen bathroom faucet.