Water appears while the sink is unused
A pressurized connection, another fixture or water traveling from elsewhere may need inspection.
Notice next: With the cabinet left undisturbed, note whether droplets form at a visible valve or tube.
United States guidance50 states + DC context
Plumbing answer · Under-sink water
Where is water under my sink coming from?
Dry the cabinet only if it is safe, stop using the sink and observe when fresh moisture returns. Water appearing while the faucet is off points to a different inspection path than water appearing only while the basin drains, but neither pattern proves a diagnosis.
If water is continuous, a supply tube or valve is visibly spraying, the cabinet is deteriorating, or electricity is nearby, shut off the accessible fixture supply and arrange prompt help. Do not force a stuck or corroded valve.
Put safety before diagnosisA wet cabinet can conceal electricity, sharp damage and mold-prone materials. Do not reach around powered equipment or force plumbing controls that may break.
Need a plumber?Confirm request and continue to callLocation changes the boundary, not the evidence
Where is the property?
Choose a state and optionally add a city and ZIP. This does not create a separate location page; it makes the limits of the answer visible.
U.S. national guidance
What changes after you choose a location?
Choose a state to make the geographic boundary explicit.
A ZIP helps identify possible utilities and service areas, but it does not prove jurisdiction, address-level coverage or an available plumber.
Applies nationallyThe safety and observation sequence on this page is general U.S. guidance.
Must be confirmed locallyUtility ownership, permits, trade licensing, rental responsibility, codes, prices and provider availability require current evidence for the exact property.
Start with observable differences
Which pattern best matches the home?
Water appears while the faucet runs
The faucet body, connections and water splashing past the sink rim are distinct possibilities.
Notice next: From above the cabinet, note whether water is also collecting around the faucet base or counter.
Water appears as the basin drains
This timing makes the drain assembly an inspection target but does not identify a particular seal or fitting.
Notice next: Stop the test after the first fresh moisture and record its highest visible point.
Safe observation
What should you record before the call?
A short, factual description helps the next professional choose the right first inspection without treating a symptom as proof.
Timing can narrow the inspection sequence, but water may travel across tubing and cabinet surfaces, so it cannot confirm the failed part.
What to record
- Whether moisture returns with the faucet off, while water runs or only while the basin drains.
- The highest visible fresh droplet or wet surface.
- Whether a dishwasher, filter, disposal or refrigerator line shares the cabinet.
- Condition of the cabinet base, nearby wall and flooring.
- Whether accessible fixture shutoffs change the leak without being forced.
Stop and get appropriate help
- Stop and isolate electrical power through a safe, dry control if water is near a disposal, outlet or powered appliance; otherwise call qualified help.
- Do not operate a garbage disposal while inspecting water beneath the sink.
- Stop using the sink if the drain releases dirty water into the cabinet.
- Request urgent help if a valve or supply connection sprays or will not close safely.
Short answers
Questions people ask before the call
Can I assume the P-trap is leaking?
No. Drain fittings are one possibility, but faucet connections, supply tubing, appliances and water from above can collect in the same cabinet.
Should I keep running water to locate the drip?
Stop once fresh moisture is observed. Repeated testing can add damage and is inappropriate near electrical equipment.
Can I force a shutoff valve that will not turn?
No. A stuck or corroded valve can fail when forced; use the main shutoff only if you know it is safe, or call a plumber.
Sources and boundaries
What supports this guide?
- U.S. EPA WaterSense — Home MaintenanceLeak, toilet, faucet, fixture and household water-maintenance observations. Scope: national. Confirm address-specific requirements with the relevant local authority or qualified professional.
- U.S. CDC — Safety Guidelines: Reentering Your Flooded HomeStanding-water, sewage and electrical safety boundaries. Scope: national. Confirm address-specific requirements with the relevant local authority or qualified professional.
Educational information only: this page cannot inspect the property, diagnose hidden work, provide legal advice, quote a repair or promise service availability.
Sources support the general guidance shown here. Address-specific rules, responsibility, price and availability still require current local confirmation.
If conditions are unsafe or rapidly worsening, stop troubleshooting and contact the appropriate emergency service or qualified local professional.