Moen Bathroom Faucet – Moen generalized faucets are so called because the handles are separated by the beak without being visibly joined. The water supply lines connect to each individual handle, and the handles are attached to the peak by flexible hoses hidden under the sink. Cartridges located on each handle control the flow of water. When the key leaks, the fault is usually with worn rubber O-rings or seals on the cartridges or valve inlets. You can correct leaks by removing the cartridge.
Disconnect the water to the faucet, turning off the angle-stops. That are closing the valves protruding from the wall under the cabinet. And then, remove the handle by unscrewing the nut. On some models, this is located on the top of the handle. Unscrew the retaining nut that holds the cartridge in place with the channel locking pliers. Grip the stem of the cartridge valve with the pliers and pull it straight out.
Examine the rings around the cartridge and replace them if they are worn. Use a screwdriver to pry the seal around the inlet hole. Insert the cartridge, or a replacement, in the same orientation was when it was removed. Open the tap, then re-activate the angular stop. Turn off the key and check for leaks.