Things You'll Need
The Moen 7400 faucet series of kitchen faucets is part of the fixture maker's Chateau collection. The 7400 features chrome finish, a single-handle mixing valve controlled by a lever, a rotating spout and an optional spray attachment. Like all Moen faucets, those in the 7400 series have removable cartridges. Although the cartridges are designed for durability, they do eventually wear out. A persistent leak, insufficient water flow or an inability to control water temperature are all signs that it may be time to replace it with a new Moen 1255 cartridge.
Turn off the water to the faucet by turning off the angle stops, or shut-off valves, located under the sink. Open the faucet to allow water to drain.
Pry off the cap that hides the screw holding the handle to the valve stem from the front of the faucet with a slot screwdriver. It is located just under the lever.
Unscrew the screw with an Allen wrench and pull the handle off the top of the faucet. Lift off the dome to reveal the retaining nut that holds the cartridge in place.
Unscrew the retaining nut with a pair of slip-lock pliers. If it is stuck, spray a little lubricant into the threads and allow it to work for five minutes, then try again. When you have removed the nut, discard it with the old cartridge. You must use a new nut to hold the replacement cartridge. It is supplied with the cartridge.
Grip the stem on the top of the cartridge with the pliers and pull upward to remove the cartridge from the valve seat. Note the orientation of the cartridge before you remove it.
Drop a new cartridge into the valve seat in the same orientation as the old one and screw on the new retaining nut. Replace the dome, then screw on the handle and push the plug that covers the screw into place with your fingers. Turn on the angle stops and test the faucet.
When the faucet is removed, you have a good opportunity to inspect the rubber seals around the valve seats and replace them if they are worn.
Be sure to turn off the water before you unscrew the nut that holds the cartridge. You can be scalded by hot water if you forget to do this.