Water Leak Under Sink: Quick Fix Guide (Troubleshooting Guide)

On this page

Quick answer
Confirm the symptom
Tools and prep
Step-by-step troubleshooting
Common causes table
Parts matching
When to call a pro
FAQ
Related guides

Quick answer

First, turn off the water supply valves under the sink. Place a bucket to catch dripping water. Check for obvious leaks from the supply lines or drain. Tighten connections or replace damaged parts as needed.

Confirm the symptom

Water pooling under the sink
Damp or wet cabinets
Musty odor under the sink
Visible water dripping from pipes or connections
Water damage on the floor or baseboards

Tools and prep

Adjustable wrench
Slip-joint pliers
Bucket and towels
Flashlight
Replacement parts (if needed)
Turn off water supply valves under the sink
Ensure the area is well-lit
Clear the space under the sink for easy access

Step-by-step troubleshooting

Access the Area
Do: Clear out items from under the sink to access the plumbing.
Observe: Check for visible leaks or water damage.
Means: Use a flashlight to inspect hard-to-see areas.
Next: Identify the source of the leak.
Identify the Leak Source
Do: Check the water supply lines, drain lines, and connections.
Observe: Look for dripping water, corrosion, or moisture.
Means: Feel for dampness with your fingers if it's not obvious.
Next: Determine the cause of the leak.
Tighten Loose Connections
Do: Use an adjustable wrench to tighten any loose connections.
Observe: Ensure connections are secure but not over-tightened.
Means: Avoid using excessive force to prevent damage.
Next: Check if the leak has stopped.
Replace Damaged Parts
Do: If tightening doesn't work, replace damaged supply lines or fittings.
Observe: Ensure new parts match the old ones in size and type.
Means: Use slip-joint pliers for better grip on fittings.
Next: Reassemble and test the plumbing.
Check the Drain
Do: Inspect the drain pipe for leaks or cracks.
Observe: Look for water pooling around the drain.
Means: Use a bucket to catch water while testing.
Next: Replace the drain pipe if necessary.
Test the Repair
Do: Slowly turn on the water supply valves.
Observe: Check for any remaining leaks.
Means: Use towels to catch drips if needed.
Next: Monitor the area for a few hours to ensure the leak is fixed.

Common causes

Cause	Likelihood	Difficulty	Part often needed
Loose connections Vibrations or wear and tear can loosen fittings.	Common	Easy	None (tightening only)
Corroded pipes Old pipes can corrode over time, leading to leaks.	Sometimes	Medium	Replacement supply lines
Damaged supply lines Kinks or cracks in the lines can cause leaks.	Sometimes	Easy–Medium	New supply lines
Faulty drain Cracks or damage to the drain pipe can lead to leaks.	Sometimes	Medium	New drain pipe
Clogged drain Blockages can cause water to back up and leak.	Sometimes	Easy	Drain cleaner or snake
Faulty garbage disposal Leaks can occur from the disposal seal or connections.	Rare	Medium	New disposal or seals

Parts matching

Ensure you have the right parts before starting the repair. Match the new parts to the old ones in size and type.

Supply line hoses
Pipe fittings and connectors
Drain pipes
Plumber's tape (Teflon tape)
Pipe joint compound
Replacement drain assembly
Garbage disposal seals

Take the old part to the hardware store to ensure a perfect match.

When to call a professional

If the leak is severe and causing significant water damage
If you cannot identify the source of the leak
If the plumbing system is complex and you're unsure about the repair
If the leak persists after attempted repairs
If you suspect a hidden leak behind walls or under floors
If you're not comfortable performing the repair yourself

FAQ

How do I turn off the water supply to the sink?

Locate the valves under the sink and turn them clockwise to shut off the water.

Can I use duct tape to fix a leak?

Duct tape is not a reliable long-term solution for plumbing leaks. Use plumber's tape or replace the damaged part.

What if the leak is coming from the wall?

A leak from the wall may indicate a more serious issue. Turn off the main water supply and call a professional plumber.