A loose retaining ring, a chipped or cracked ball, and a broken spring are common leak sources in ball-valve faucets such as a Kohler washerless faucet. Repair the leak by tightening the retaining ring. If the ball or the spring is the problem, replace it.
A cracked or chipped cartridge and damaged O-rings are common problems in cartridge faucets. Replace the cartridge or the O-rings to repair the faucet. Worn-out seals and a cracked or defective disk mechanism are common leak sources in ceramic disk faucets. Remove the worn-out seals, and replace them with new ones. If the entire disk mechanism is malfunctioning, the only way to fix it is to replace the handle.