Toilet Leaking — fill valve

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

1. Check 1

   Stand on a dry surface and locate the first wet point without reaching through water: the floor at the supply line, the tank bottom or fill-valve shank, the tank rim/overflow tube, the bowl/base, or a wall/floor penetration. If water is actively escaping and the toilet stop is accessible and moves normally, turn that stop clockwise to close it; do not force it.

   Expected result: The leak slows or stops at the supply stop, continues from the tank or bowl, appears only after flushing, or cannot be safely reached or controlled.

   Next step: Keep the toilet out of use, protect the floor from further damage, and call a plumber if the stop does not control the leak or the first wet point is concealed.

   Stop if: Stop for sewage, an overflowing bowl, water near electrical equipment, a soft or sinking floor, cracked porcelain, a seized stop, or active water that cannot be controlled.

   Why this matters

   Why: A supply-stop response supports an external supply-side path; continued water from the tank or bowl needs a tank/flush diagnosis. An inaccessible or uncontrolled leak may involve the stop, concealed piping, or a larger plumbing failure.

2. Check 2

   When the area is dry and the bowl is not backing up, look inside the tank without touching the valve. Note whether water continues to enter after the tank reaches its normal level, whether the water rises toward or over the overflow tube, and whether the floor or tank exterior becomes wet at the fill-valve connection.

   Expected result: Water keeps running into the tank, reaches the overflow tube, stops below the overflow, or appears outside at the valve shank/locknut or supply connection.

   Next step: Do not adjust, remove, or replace the fill valve while water is escaping or the connection is wet. Record the exact location and ask a plumber to verify the valve, float setting, gasket, and supply connection.

   Stop if: Stop for water over the overflow, a loose tank, cracked porcelain, corrosion that could break when touched, or water near electrical equipment.

   Why this matters

   Why: Continuous inflow or overflow supports a fill-valve/float-level problem. Exterior wetness at the shank or supply connection is a seal or connection leak, not proof that the internal valve mechanism is faulty. Water below the overflow with no exterior wetness points elsewhere, including the flapper path.

3. Check 3

   If there is no active external leak and the tank can be observed safely, compare the water level with the overflow tube and watch whether the fill valve shuts off after a normal refill. Do not bend a float, remove the valve cap, or turn a small adjustment screw unless the exact toilet instructions expressly identify that user adjustment.

   Expected result: The valve shuts off at a stable level below the overflow, keeps running, intermittently starts, or the water level changes after the toilet has not been flushed.

   Next step: Move to the dye and bowl check if there is no floor/tank exterior leak. If the valve cannot shut off or the level approaches the overflow, close the supply stop and call a plumber.

   Stop if: Stop if the tank overflows, the water cannot be stopped, the porcelain moves or cracks, or a valve adjustment would require tools or contact with a wet fitting.

   Why this matters

   Why: A stable level makes an overflowing fill valve less likely. Continued or intermittent inflow can come from the fill valve/float, supply pressure behavior, or water leaving through the flush seal; the observation alone does not identify a replacement part.

4. Check 4

   To distinguish a silent tank-to-bowl leak from a fill-valve overflow, only when the tank is stable and the bowl is clear, add a few drops of food coloring or a dye tablet to the tank without flushing. Wait 10 minutes, then look for color in the bowl and flush afterward to avoid staining.

   Expected result: Color appears in the bowl during the wait, or the bowl stays clear while the tank level and exterior remain stable.

   Next step: If color appears, report a flush-seal leak to a plumber. If the bowl stays clear but the fill valve runs or leaks outside, report the fill-valve or connection symptoms instead.

   Stop if: Do not perform the dye check with an overflowing or backed-up bowl, active sewage, uncontrolled water, or a tank that may be unstable; stop if color cannot be flushed safely.

   Why this matters

   Why: Color in the bowl indicates water is crossing the flapper or flush-valve seal; it does not diagnose the fill valve. A clear bowl makes a silent flapper leak less likely, so an earlier overflow or connection observation deserves more weight.

5. Check 5

   From a dry position, inspect the visible supply hose, shutoff, tank underside, and floor around the toilet for a repeatable drip pattern. Do not tighten the nut, remove the hose, lift the tank, or wipe a fitting while it is under pressure or actively leaking.

   Expected result: The first wet point is the supply stop/hose, the fill-valve shank through the tank, the tank-to-bowl joint, the bowl base, or a wall/floor penetration.

   Next step: Keep the supply closed if possible and have a plumber repair the identified connection or investigate the concealed path; do not substitute a new fill valve for an unverified leak source.

   Stop if: Stop for sewage, porcelain cracks, tank movement, a soft floor, water entering a wall/ceiling, or any fitting that is corroded, seized, or likely to break.

   Why this matters

   Why: The location separates a supply connection, fill-valve gasket/shank, tank seal, bowl seal, or concealed plumbing path. A leak at the bowl base or wall/floor penetration is not a safe fill-valve replacement diagnosis.

6. Check 6

   Prepare the plumbing-service handoff: note the first wet point, whether it occurs during refill or between flushes, whether the supply stop controls it, tank water level relative to overflow, dye-test result, toilet make/model if visible, and any recent repair or part change.

   Expected result: The leak is externally controlled, an internal fill-valve/overflow symptom, a tank-to-bowl seal symptom, or a concealed/base leak that needs professional isolation.

   Next step: Leave the toilet unused or with its supply closed until the leak is repaired whenever water damage, sewage, overflow, or an uncontrolled connection is possible.

   Stop if: Stop all homeowner work if the source remains unclear, the leak returns after a safe observation, or repair would require removing a tank, disconnecting a pressurized line, or handling damaged porcelain.

   Why this matters

   Why: A time-and-location record prevents a plumber from treating every toilet leak as a fill-valve failure and helps identify whether a conditional valve, gasket, flush seal, tank seal, or supply repair is appropriate.