Faucets leak for a variety of reasons from loose or broken supply tubes, to a worn out ceramic disk. If you have a leaking faucet, you can diagnose the origin of the leak based on where the faucet is leaking from.
Faucet Base is Leaking
If the faucet’s base is leaking the problem is with the cartridge. This is the valve that moderates the flow of water into the spout. The water is flowing up into the base of the faucet, and coming out through a crack in one of the disks in the cartridge.
Solution: Replace the cartridge and O rings.
Spout Leaks or Drips Constantly
If the spout drips or leaks constantly the problem is also with the cartridge. The cartridge seal is broken and water is passing up into the spout. Even a small crack in the cartridge or a scratch from a grain of sand will cause a spout to leak constantly.
Solution: Replace the faucet cartridge.
Supply Lines Drip or Stream Water
If the supply lines are dripping or streaming water a few things may be wrong. The cartridge might be broken and water is simply leaking out and down the faucet’s base and along the supply lines. If this is the problem, your faucet base gasket or plumber’s putty seal is also faulty and needs replacing.
Solutions: Replace cartridge, base gasket.
Another possibility is a loose supply hose connector. Just tighten the connector with a basin wrench, to fix this problem.
If tightening the connector does not stop the leak, your supply line connector might be stripped, or the supply tube could be damaged. Either way, you need to replace the supply by shutting off the water and removing the old one in exchange for a new one.
Solutions: Tighten or replace supply tubes.