Sink Running in an Upstairs Bathroom: Separate No Flow from Water That Will Not Stop

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

1. Check 1

   From a dry position, write down what “not running” and “not stopping” mean at this sink. Observe each hot and cold handle or control separately, and identify whether water is absent, drips, streams from the spout with the control closed, or leaks below the basin.

   Expected result: Both sides have no flow, only one side has no flow, water streams with the control closed, or water is leaking below the sink while the spout is dry.

   Next step: Keep the control in its normal closed position, do not leave the water running to reproduce the symptom, and continue with scope and shutoff observations.

   Stop if: Stop immediately for rapid flow, water entering the wall or floor, standing water, or water near electrical equipment.

   Why this matters

   Why: No flow and uncontrolled flow are different paths. A missing hot or cold side favors a supply or faucet-side restriction, while a stream with the control closed favors a faucet flow-control problem or a supply that has not been isolated.

2. Check 2

   Check another fixture in the upstairs bathroom and one fixture on a different floor without changing any plumbing. Note whether cold and hot water are available elsewhere and whether other drains or fixtures are also affected.

   Expected result: Only this sink is dry or uncontrolled, both upstairs fixtures are affected, hot and cold are affected differently, or the whole home has weak or absent water.

   Next step: Leave the affected sink unused and record the scope. Do not open fittings or repeatedly operate fixtures to chase the symptom.

   Stop if: Stop for ceiling stains below, active leakage, sewage backup, or any need to enter a wet area or concealed space.

   Why this matters

   Why: A single-sink symptom points toward local shutoffs, hoses, faucet, or drain. Two fixtures on the same floor suggest a branch or local supply issue; a wider loss suggests the home supply, main shutoff, or utility.

3. Check 3

   From outside the cabinet, locate the sink's hot and cold shutoff valves and observe whether each appears open, closed, wet, damaged, or connected to a kinked hose. Do not force a valve or use a tool on a connection.

   Expected result: A valve is clearly closed, a hose is kinked, the valve or hose is leaking, both valves appear open, or the valves cannot be reached safely.

   Next step: If the area is dry and the valve works normally, restore a clearly closed valve once and observe. If a valve leaks, spins, or will not operate, leave it alone and call a plumber.

   Stop if: Stop for spray, a seized or spinning valve, a cracked hose, water in the cabinet, or electrical equipment in the wet area.

   Why this matters

   Why: A closed local supply can explain no flow; a wet or damaged valve or hose can explain uncontrolled water. Apparently open valves do not prove the faucet or branch is clear.

4. Check 4

   If water continues from the spout or a supply leak after the local valves are closed, observe whether the flow decreases. From a dry, safe location, close the home's main shutoff only if the local valves do not isolate the leak and the main valve is clearly accessible.

   Expected result: The flow stops at the local valves, slows but does not stop, or continues unchanged after local isolation.

   Next step: Keep the isolated valve or main shutoff closed, protect the rooms below, and contact a licensed plumber. Do not dismantle the faucet or pipe while pressure or flow remains.

   Stop if: Stop for uncontrolled flow, a main valve that will not close, water entering a wall or ceiling, or any electrical hazard.

   Why this matters

   Why: A local shutoff that works narrows the fault to the sink fixture or its local supply. Continued flow may indicate a failed valve, an upstream connection, trapped water, or a separate source.

5. Check 5

   With the local supply isolated and the area dry, inspect the faucet outlet, handle or sensor area, base, underside connections, basin rim, and cabinet for the first wet point. Do not remove the handle or body.

   Expected result: The first wet point is the spout or control, faucet base, supply connection, basin rim, or no visible sink point while water appears below.

   Next step: Photograph the first wet point and provide the faucet model to the builder, manufacturer, or plumber. Keep the supply isolated until the correct repair is confirmed.

   Stop if: Stop if finding the source requires opening the wall, lifting the basin, forcing the faucet, or handling contaminated water.

   Why this matters

   Why: A spout or control that drips or streams while closed can involve the faucet's internal flow-control component. A base or underside leak may be a seal or connection. Water below without a visible sink source may be traveling from a concealed pipe or nearby fixture.

6. Check 6

   If the sink has a touchless, sensor, or powered control, observe its indicator and power status without reaching into the control box or moving cables. If it has an ordinary handle, use the handle position and the first wet point instead; do not apply sensor guidance to a non-sensor faucet.

   Expected result: A sensor faucet shows an alert or erratic behavior, a powered control is unresponsive, an ordinary handle is fully closed but water continues, or the faucet type is unknown.

   Next step: Record the exact faucet type and model, keep the water isolated, and use only the manufacturer's instructions or a plumber. Do not reset repeatedly or disconnect powered controls under the sink.

   Stop if: Stop for wet electronics, a damaged cord, heat, smoke, or any need to access wiring or a control box.

   Why this matters

   Why: Electronic controls can create model-specific open or close behavior, while a conventional faucet that streams when closed may have an internal cartridge or valve issue. Unknown type means the model manual is needed.

7. Check 7

   Observe the drain, P-trap, wall-side drain, and ceiling or wall below from outside the cabinet only. If the sink has no active supply leak and the floor is dry, run a very small amount of water once to see whether the drain path is the source; stop at the first sign of backup or leakage.

   Expected result: Water appears only while draining, the basin backs up, the trap or wall connection is wet, or water is present below without an active sink supply.

   Next step: Stop using the sink, keep the affected area isolated, and call a plumber. Do not pour chemical cleaner, open the wall, or continue testing upstairs water over a room below.

   Stop if: Stop for dirty backup, sewage odor, ceiling damage, water near electrical equipment, or any concealed leak.

   Why this matters

   Why: A drain, branch, or concealed pipe can mimic a faucet that will not stop, especially when water travels inside the cabinet or floor. A drain problem does not justify changing the faucet cartridge.

8. Check 8

   Prepare a service record with the exact wording of the symptom, both fixture observations, hot and cold results, valve positions, first wet point, timing, photos, and whether the local or main shutoff changed the flow. Keep the upstairs sink unused until the source is resolved.

   Expected result: The issue is isolated to the faucet, local supply, branch, drain, main supply, or remains uncertain after safe external checks.

   Next step: Call a licensed plumber and, if the home is new or under warranty, notify the builder or property manager with the same evidence. Do not assign responsibility or buy a part before the source is identified.

   Stop if: Stop all homeowner diagnosis when the source is hidden, flow cannot be isolated, damage is spreading, or repair would require opening plumbing or a wall.

   Why this matters

   Why: A clear record lets a plumber separate no flow from uncontrolled flow and identify whether the two reported symptoms are connected or are two faults occurring in the same bathroom.