Moen bathroom faucets use a small cartridge fit inside the handle base to operate the flow of water. In the case of a two-handled bathroom faucet, this cartridge controls just one of the water lines. When turned, the top portion of the cartridge rotates, opening a valve and allowing water through. To get warm water, the user turns the hot and the cold handles slightly. The more the hot is opened and the more the cold is closed, the hotter the water gets.
Kitchen faucets work in a similar fashion. Two-handle faucets each have a cartridge in the handle to turn on the hot or cold water. The two mix inside the spout as the water flows into the faucet from the two supply lines beneath the cabinet. In the case of a single-handle faucet, there is only one cartridge, and both hot and cold water lines flow through it. This cartridge, therefore, has two valves, and, when the handle is lifted and turned, the valves open, allowing either hot or cold water through.
The kitchen faucet sprayer is attached to the main faucet by a hose that connects to the base of the faucet. The water flows through the faucet and to the end of the sprayer when the faucet handle is lifted and turned to the "On" position. However, water only flows out of the spout until the sprayer handle is depressed. When this happens, the sprayer valve opens and the water flows out of the sprayer. If your faucet is a pull-down style, with the sprayer attached to the base of the faucet, there is a hose connected to the head of the sprayer and faucet base. The sprayer is operated by depressing a button on the end of the spray head.
Tub and Shower Faucets
Most Moen tub and shower faucets are a single-handle design, which means only one handle controls the hot and cold water flow rates. This unit also has a cartridge inside the base of the faucet. When the handle is lifted, the cartridge valves open and water flows through. Turning this to one side or the other lets the hot or cold water through because now the hot or cold water valves are lined up inside the cartridge. The faucet installs on the shower wall with a back plate called an escutcheon. It connects to a diverter which is soldered in place on the hot and cold water pipes. This is a Moen diverter, which allows the base of the faucet to be installed on the pipes.