Sink Leaking After the Water Was Shut Off in a New House

Use only checks that match the exact appliance or system and its official guide.

1. Check 1

   Keep hands and the floor dry, move stored items only if they are safe to handle, and close the sink's local hot and cold valves if they are clearly identified and reachable without entering water. If water is spreading or a valve will not stop it, close the home's main water shutoff from a dry location.

   Expected result: The leak slows or stops at a local valve, continues despite local valves being closed, or is close to an outlet, disposal wiring, or other electrical equipment.

   Next step: Stop the inspection for electrical exposure, uncontrolled flow, smoke, burning odor, or shock. Otherwise keep the isolated valve closed and continue with dry external observation.

   Stop if: Do not touch wet electrical equipment, repeatedly operate a stuck valve, or stand in water to reach a shutoff.

   Why this matters

   Why: A local valve that isolates the leak points toward the sink fixture or its supply; continued flow suggests a valve, upstream connection, trapped water, or concealed line. Water near electricity is an immediate safety problem.

2. Check 2

   Blot the cabinet floor and place separate dry towels around each angle stop, hot and cold supply hose, faucet base, faucet outlet, drain strainer, P-trap, and wall-side pipe. Mark which towel becomes wet first and whether the wetness grows while the sink is idle.

   Expected result: The first wet point is a shutoff valve or supply hose, faucet or base, drain joint, or the wall-side connection; the leak is idle, faucet-on, or drain-only.

   Next step: Follow the matching branch without tightening every fitting or assuming the lowest puddle is the source. Photograph the first wet point before any repair attempt.

   Stop if: Stop if locating the first wet point requires removing a panel, opening a wall, moving a fixed appliance, or entering a wet or contaminated area.

   Why this matters

   Why: An idle leak favors a pressurized supply or valve connection. A leak only while draining favors the strainer, trap, branch, or wall connection. A faucet-on leak favors the faucet body, hose, or outlet path.

3. Check 3

   Inspect each new-house shutoff valve and supply hose externally for a wet stem, valve body, compression connection, kink, damaged washer, or hose end. Do not use a wrench on a wet or rotating valve, and do not force a connection that is still pressurized.

   Expected result: Moisture begins at the valve stem or body, the hose end, or the connection where the hose meets the faucet or house piping, and the leak changes when that valve is isolated.

   Next step: Leave the affected valve closed, retain photos and the installation date, and notify the builder or warranty contact and a licensed plumber. Replace or tighten only when the exact installation instructions authorize it and the area is dry and depressurized.

   Stop if: Stop for a valve that spins without isolating water, a cracked hose, a spray, corrosion, or water entering the wall or floor.

   Why this matters

   Why: The supply-side installation is implicated. A new installation can still have a loose, misaligned, damaged, or defective connection, but the correct repair depends on the actual fitting and local code.

4. Check 4

   Check the faucet and basin externally for water at the spout, handle or body, deck gasket, base, and the underside of the faucet connections. Keep the local valves closed while checking; do not remove the faucet or use a tool simply because the home is new.

   Expected result: The faucet base or connection is wet while supply is available, the outlet only drips briefly after shutoff, or water appears to run along the counter into the cabinet.

   Next step: Keep the valves closed, dry the area, and have the builder or plumber verify the faucet mounting, seals, and hose connections against the exact fixture instructions.

   Stop if: Stop if the faucet body is cracked, the water cannot be isolated, or the leak reaches an electrical device or hidden cavity.

   Why this matters

   Why: A brief residual drip can be water draining from the faucet, but continuing moisture at a base or connection indicates a fixture seal or supply issue. Water tracking from the countertop can mimic a pipe leak.

5. Check 5

   If no supply point is wet, make one brief drain observation only when the cabinet and floor are dry and there is no electrical or sewage hazard. Pour a small amount of cold water into the basin, then watch the strainer, tailpiece, P-trap, and wall connection from outside the cabinet.

   Expected result: Water appears only while the basin drains, backs up in the sink, or emerges at the wall-side drain; or the drain remains dry while the sink is idle.

   Next step: Stop using the sink if it backs up or leaks at the wall, keep the water isolated, and arrange plumbing service. Do not pour chemical drain cleaner into a new-house system or disassemble a line containing chemicals.

   Stop if: Stop for dirty backup, sewage odor, ceiling or wall staining, cabinet damage, or water near electrical equipment.

   Why this matters

   Why: A drain seal, trap, branch, or concealed drain connection is more likely than a supply leak. A wall-side leak may be hidden behind the cabinet or wall and is not a reason to keep testing.

6. Check 6

   After the area is dry and the source is documented, restore water only once and only from a safe location if the leak was fully isolated and no hazard is present. Watch the same marked points as pressure returns, then close the local valve again if moisture reappears.

   Expected result: The leak returns immediately when water is restored, appears only after the faucet or drain is used, or does not return while the sink and house are idle.

   Next step: Do not repeat the cycle. Give the builder and plumber the photos, timing, valve positions, and first wet point; ask them to verify the installation and any warranty response.

   Stop if: Stop immediately for spray, rapid pooling, hidden moisture, a stuck shutoff, smoke, burning odor, or any electrical symptom.

   Why this matters

   Why: Immediate recurrence supports a pressurized supply or fixture connection; use-related recurrence supports the faucet or drain path. No recurrence does not prove the installation is sound if there is trapped water or a concealed leak.

7. Check 7

   Record the home's age and occupancy date, when the water was shut off, which valve was used, whether any plumbing work preceded the leak, the first wet point, photos, and whether the leak returned after water was restored. Do not assign fault solely from the phrase new house.

   Expected result: The evidence identifies a fixture connection, supply valve or hose, drain, or concealed path; or the source remains uncertain after safe external checks.

   Next step: Keep the affected valve or main supply closed as needed and contact the builder's warranty channel and a licensed plumber. Request a written diagnosis and preserve damaged materials and photos.

   Stop if: Stop DIY work when the source is concealed, the leak persists, or the repair would require opening walls, changing house piping, or working on a pressurized connection.

   Why this matters

   Why: A clear location helps separate a builder or fixture installation issue from a drain or house-piping problem, while an uncertain source needs professional tracing rather than guesswork.