What this leak is telling you
A spout drip means the valve isn't shutting off. A leak around the handle means water is getting past a seal that's supposed to keep it inside the faucet body. The parts involved are small: usually an O-ring, a packing nut, or the cartridge itself.
Notice when it happens. If water appears only while the faucet is running, the seal around the stem or cartridge is the likely cause. If it seeps when the faucet is off too, the cartridge may be cracked or loose in its seat.
The usual causes
Worn O-rings
The rubber rings around the cartridge or stem dry out and flatten with age. This is the most common cause, and the parts cost very little.
A loose packing nut or retaining nut
The nut that holds the cartridge in place can work loose over years of turning the handle. Sometimes it just needs to be seated properly, with new seals fitted while things are open.
Mineral buildup
Scale on the stem chews up the O-ring every time the handle turns. Cleaning the parts and replacing the seals solves it.
A cracked cartridge
Often the result of a handle being forced when it was stiff. This is why a hard-to-turn handle is worth fixing early.
What you can check first
- Dry the faucet completely, then run it and watch closely. Confirm the water is coming from the handle area and not running down from the spout or up from the base.
- Look for a small set screw under a cap on the handle. If the handle is loose, the screw may have backed out.
- Check under the sink for water. A handle leak can run down the back of the faucet and show up as a wet cabinet, which is covered in fixing a leak under the sink.
How the repair goes
The water gets shut off at the valves under the sink. The handle comes off, then the retaining nut, then the cartridge or stem. The O-rings get replaced, the seat gets cleaned, and everything goes back together with the parts seated correctly. On a two-handle faucet, only the leaking side usually needs the work.
The tricky part is removing a cartridge that's been in place for years without damaging the faucet body. Cartridge pullers exist for this reason. Twisting hard on a stuck cartridge is how bodies get cracked.
Don't ignore a handle leak
Water running down the outside of a faucet gets under the base and onto the sink deck. Over time it can work through to the cabinet below and damage the countertop edge or the particleboard underneath. It's a small repair now and a bigger one later.
For leaks somewhere else on the faucet, see leaking faucet repair. For handles that are stiff, loose or broken, see faucet repair.