To determine which parts are needed to repair a leaky bathroom sink faucet, determine the type of faucet that is installed and troubleshoot for causes of leaks common to that construction type. Once the source of the leak is determined, replace the faulty part.
Most commonly, a leak in a compression faucet is due to a badly seated washer. This type of leak is repaired by replacing the washer and O-ring. If the faucet continues to leak, the seat may have become pitted. This is repaired by grinding the stem smooth with a valve-seat dresser. Leaks in a ceramic disk faucet can generally be repaired by removing sediment around the seals or replacing the seals and O-ring. If the faucet continues to leak, the cartridge may need replacing. Leaks in cartridge faucets are most frequently repaired by replacing and properly sealing the O-ring. If the faucet still leaks, a replacement cartridge is needed. Because of the complexity of ball-type faucets, it is recommended that this type of faucet is replaced entirely if it leaks.
Before troubleshooting or making repairs to a bathroom faucet, turn off the water supply. Closing the sink drain and covering it with a cloth makes it easier to retrieve dropped parts, and covering the jaws of wrenches with duct tape prevents scratches on the faucet fixtures.