How to Find the Source of an Under-Sink Leak

Understand the job

Water can travel along a pipe or cabinet surface before it drips, so the wettest spot is not always the source.

What to inspect first

Empty and dry the cabinet completely. Check supply valves and hoses first, then faucet connections, drain joints, disposal flange and dishwasher connection if present.

Step-by-step approach

Use dry paper towels at each connection and run one test at a time: hot water, cold water, full sink drain and disposal or dishwasher as applicable.

Common warning signs

Swollen cabinet bottoms, soft flooring, active supply leaks or corrosion at shutoff valves may require prompt repair and drying.

Final checks

After repair, dry everything and repeat the same test sequence before putting stored items back.

Tools and materials to plan for

The exact list depends on the product and site. Plan for accurate measuring tools, suitable personal protection, manufacturer-approved fasteners or fittings, cleanup supplies and a reliable way to verify the finished work.

Common mistakes to avoid

• Replacing parts before identifying the cause
• Skipping measurements or manufacturer instructions
• Using fasteners, sealants or materials not rated for the application
• Closing the repair before checking for hidden damage
• Failing to test the completed work before calling it finished

Should you DIY or hire help?

Straightforward inspection and maintenance may be reasonable for a careful homeowner. Hire qualified help when access is difficult, the repair crosses multiple trades, permits or licensing may apply, structural or electrical conditions are involved, or the problem keeps returning after a basic repair.