Fix a Kitchen Sink Leaking From the Base

A leak from the base of the faucet (not the drain) almost always means one thing: the O-rings or base gasket have failed. This is a DIY fix in 30–60 minutes with basic tools and costs under $20 in most cases. Do not ignore it — water pooling under the sink causes cabinet rot and mold within weeks.

Step 1 — Confirm the Source

Dry everything under the sink completely, then run the faucet and watch carefully. Leak from the faucet base = O-ring/gasket issue. Leak from the drain flange = putty seal issue (different fix — see below). Leak from supply lines = tighten or replace the lines.

Step 2 — Faucet Base Leak Fix (Most Common)

1. Shut off both water supply valves under the sink (hot + cold). Turn clockwise until firm.
2. Turn on the faucet to release pressure and drain remaining water.
3. Remove the faucet handle (usually a set screw under a decorative cap).
4. Unscrew the packing nut and pull out the cartridge or stem.
5. Inspect the O-rings — they will be cracked, flattened, or brittle.
6. Replace O-rings with exact-size matches (bring the old ones to the hardware store or measure diameter).
7. Coat new O-rings lightly with plumber's grease before installing.
8. Reassemble, turn water back on slowly, and test.

Step 3 — Drain Flange Leak Fix

1. If water leaks when you fill the sink and drain it, the drain flange seal is the culprit.
2. Unscrew the drain basket from below using pliers or a drain wrench.
3. Scrape off old plumber's putty from the flange and sink hole.
4. Roll fresh plumber's putty into a rope, press it around the drain flange, and reseat it.
5. Tighten from below, wipe excess putty, and test.

Step 4 — Supply Line Leak

If the braided lines running from the shutoff valves to the faucet are dripping, simply hand-tighten the nuts first. If they still leak, replace the supply lines — they cost $8–12 and are the single most common cause of under-sink water damage.

Pro tip: While you have the water off, check the age of your supply lines. If they are rubber-braided and more than 5–7 years old, replace them proactively — they burst without warning and can flood your kitchen. Stainless steel braided lines last significantly longer.