How to Fix a Leak in a Bathroom Sink (DIY Troubleshooting Guide)
A dripping bathroom sink wastes water and can damage your vanity over time. Here’s a practical, homeowner-friendly way to find the source and fix the most common leaks.
Before you start: safety + quick checks
Turn off the water if you’ll be loosening any connections. Put a towel and a small bucket under the sink, and keep a flashlight handy.
Step 1: Identify where the leak is coming from
Dry everything under the sink, then run the faucet for 30–60 seconds and watch closely. Most leaks come from one of these spots:
The drain (P-trap, slip nuts, or drain flange)
The faucet supply lines (hot/cold braided hoses)
The shutoff valves (angle stops)
The faucet base or handles (leaking above the countertop)
Step 2: Fix a leak at the P-trap or slip nuts
If the leak is at a slip nut (the plastic or metal ring where pipes join), try this first:
Hand-tighten the slip nut. If it’s already snug, give it a small additional turn with channel-lock pliers (don’t over-tighten).
If it still leaks, loosen the nut, check that the washer is seated correctly, then re-tighten.
Replace the washer if it’s cracked, flattened, or missing.
Tip: If you see corrosion or the trap is misaligned, replacing the P-trap kit is often faster than fighting a bad seal.
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Step 3: Fix a leak at the drain flange (sink drain)
If water appears around the top of the drain or drips down the tailpiece, the drain flange seal may be failing.
Remove the P-trap and tailpiece.
Loosen the locknut under the sink and remove the drain body.
Clean old putty/silicone from the sink and drain.
Apply fresh plumber’s putty (or silicone if required by your drain type), reinstall, and tighten evenly.
Step 4: Fix a leak at the supply lines
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If the braided hose connection is dripping:
Turn off the shutoff valve for that line.
Tighten the connection at the faucet and/or shutoff valve (usually 1/8–1/4 turn).
If it still leaks, replace the supply line. They’re inexpensive and often fail with age.
Step 5: When to call a pro
Call a plumber if you see cracked pipes, a leaking shutoff valve that won’t fully stop water, signs of mold/rot, or if the leak is inside the wall.
Need help finding a local pro?
Browse local service providers and get help fast here:
https://www.readyjan.com/
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Quick checklist
Dry the area and pinpoint the leak source
Tighten slip nuts and reseat/replace washers
Reseal the drain flange if needed
Tighten or replace supply lines
Call a pro for shutoff valve or in-wall leaks
