Fill valve still running after replacing the seal: what to check

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

1. Check 1

   Remove only the toilet tank lid and flush once. Keep hands clear of the float and linkage, then watch whether water enters through the fill valve, whether the tank reaches its normal level, whether water is visibly flowing into the bowl, and whether the fill sound stops.

   Expected result: The water level keeps rising, the tank reaches its level but the bowl receives a steady trickle, the valve cycles on and off, or the valve continues filling after the tank is full.

   Next step: If the tank is approaching the overflow or water is spraying, close the local supply valve. Otherwise continue with the water-loss test and seal-fit checks; do not hold the float up as a permanent repair.

   Why this matters

   Why: Water entering the bowl or a tank level that falls after filling makes a flush-valve seal, flapper, chain, or overflow path more likely. Water that remains at the correct level while the fill valve keeps flowing makes the fill-valve float, height, debris, or valve body more likely.

2. Check 2

   Mark the tank waterline with a pencil after the fill cycle, close the toilet's local supply valve without forcing it, and wait about 25–30 minutes without flushing. Check whether the tank level moved and where the bowl water is relative to its normal level.

   Expected result: The tank level drops with the supply closed, the level stays stable, or the tank empties toward the flush seal or overflow path.

   Next step: If the level drops, inspect only accessible chain, flapper, seal seating, and visible overflow routing. If it stays stable, reopen the supply slowly and continue with the fill-valve checks; call a plumber if the shutoff leaks or will not operate.

   Why this matters

   Why: A falling tank confirms water is leaving the tank independently of the fill valve; a stable tank shifts attention toward the fill valve not shutting off, its float/height, debris, or the replacement seal's internal installation.

3. Check 3

   Inspect the replaced seal and its surrounding flush-valve surface only with the supply closed and tank mostly empty. Compare the seal shape and valve style with the toilet or valve manufacturer's instructions; look for wrong size, twisting, debris, mineral buildup, cracks, or a chain holding the flapper open.

   Expected result: The seal is not the matching style, is folded or nicked, has residue on its seating surface, the chain is tight, or the sealing surface is cracked or warped.

   Next step: Use only the exact model-specific seal or flapper specified by the manufacturer and clean only accessible residue with the supply off. Stop and arrange plumbing service for cracks, warping, a seized assembly, or uncertainty about the valve style.

   Why this matters

   Why: A wrong or poorly seated seal, debris, chain tension, or damaged flush-valve seat can let tank water bypass the repair and make the fill valve cycle. A damaged seat or flush valve is not corrected by changing a fill-valve seal.

4. Check 4

   With the tank lid off and no leak hazard present, check that the fill valve sits below the overflow-tube top, its height adjustment is locked, the float can move freely without rubbing the tank, and the refill tube is clipped as intended rather than pushed down into the overflow tube.

   Expected result: The valve is too high, its adjustment is unlocked, the float catches on the tank, or the refill tube is submerged in the overflow tube; alternatively, all visible positions are correct.

   Next step: Make only the model-directed external height or tube correction, then observe one refill cycle. Do not remove the valve cap or supply connection while pressurized; if the valve still runs, close the supply and obtain service or use the exact manufacturer procedure.

   Why this matters

   Why: Incorrect valve height can prevent shutoff or risk overflow, a rubbing or stuck float can keep the inlet open, and a submerged refill tube can siphon tank water into the bowl. Correct visible positioning with continued running makes debris or a failed valve more likely.

5. Check 5

   Look around the tank bottom, supply connection, shutoff valve, bowl base, and floor while the supply is reopened slowly. Use a dry tissue on the outside of joints to identify fresh water; do not place hands inside the valve or tighten a fitting aggressively.

   Expected result: Water appears at the tank-to-bowl area, supply connection, shutoff stem, tank porcelain, or floor, or the exterior remains dry while the valve runs internally.

   Next step: Close the local supply for any external leak, cracked porcelain, or failed shutoff and arrange a plumber. If the exterior is dry, proceed only with the single safe cycle test and do not leave the toilet running unattended.

   Why this matters

   Why: An external leak is separate from a running fill-valve symptom and can worsen when the supply remains on. A dry exterior with internal running keeps the diagnosis centered on tank water loss, water level, or the fill valve itself.

6. Check 6

   After the seal and visible adjustments are confirmed, perform one supervised flush and record whether the fill valve stops at the same tank level, whether the bowl receives refill water only during the cycle, and whether the symptom returns after the toilet is idle.

   Expected result: The valve stops and stays quiet, it cycles on again while idle, it continues running at a full tank, or the symptom returns with an unexplained level drop.

   Next step: Do not keep flushing for evidence. Close the supply and call a plumber if one supervised cycle fails, water approaches overflow, the valve cannot shut off, or the cause remains uncertain.

   Why this matters

   Why: A stable full tank with no bowl flow supports a successful seal repair. Idle cycling with a falling tank points to a remaining flush-valve leak; continuous flow at a stable full tank points to fill-valve shutoff, float, debris, or valve-body trouble.