Short definition

A faucet leaking around the base has one of three problems: a worn O-ring at the spout swivel, a loose faucet mounting nut letting water under the body, or a failed putty/gasket at the deck. Each has a distinct fix and they’re easy to tell apart with a quick test.

What it is

Three causes account for almost every base-leak case:

  1. Worn O-ring at the spout swivel. Most common on kitchen faucets more than five years old. Water seeps up between the spout and the body where the spout rotates. Test: lift the spout slightly while running and watch for water emerging from the swivel joint. Fix: pull the spout, replace the O-rings ($1 to $10), lubricate with silicone plumber’s grease, reseat.
  2. Loose faucet jamb nut. The mounting nut under the sink has worked loose; the faucet body has shifted slightly and water from any spillage pools under it. Test: try to wiggle the faucet body — if it moves, the nut is loose. Fix: tighten the jamb nut from below with a basin wrench. Free.
  3. Failed plumber’s putty or deck gasket. Water spilled on the counter migrates under the faucet base and out the bottom. Test: the leak only appears after spilling water around the faucet, not from running it normally. Fix: pull the faucet, scrape old sealant, re-bed with fresh putty or silicone caulk ($5).

Why it matters to a homeowner

This is the second-most-common faucet symptom search after “drips from spout,” and it’s almost always cheaper to fix than people expect. Pro service calls run $90 to $175; the parts and effort are well within DIY range for any of the three causes.

The diagnostic order matters. Tighten the jamb nut first (free, fixes a surprising number of cases). If that doesn’t fix it, do the lift-while-running test for the spout swivel. If that’s not it either, the deck seal is the suspect — and re-bedding a faucet base is a 30-minute job.

Common variants

  • Leak around base (this entry). Three causes above.
  • Drip from spout (when off). Different problem entirely. See faucet-drips-from-spout.
  • Leak under sink at supply riser. Different problem. Fix at the riser or angle stop, not at the faucet.