How to Fix a Toilet That Won't Stop Running

How to Fix a Toilet That Won't Stop Running

A toilet that runs non-stop — not just after flushing, but continuously — is wasting up to 200 gallons of water per day. This is almost always caused by a failed flapper or a fill valve that won't shut off. Here's how to fix it fast.

Emergency First Step: Adjust the Float

If you need to stop the running immediately while you get parts, try this first:

• Remove the tank lid
• If water is flowing into the overflow tube, bend the float arm down (ball float) or slide the float down (cup float)
• This may temporarily stop the running by lowering the water level below the overflow tube

Diagnose the Cause

Test 1 — Flapper test: Press down on the flapper with your finger. If the running stops, the flapper isn't sealing. Replace it.

Test 2 — Fill valve test: Lift the float arm up. If the running stops, the fill valve isn't shutting off properly. Replace it.

Test 3 — Food coloring test: Add food coloring to the tank. If color appears in the bowl within 15 minutes without flushing, the flapper is leaking.

Fix 1: Replace the Flapper

👉 Universal toilet flapper

1. Turn off the water supply valve behind the toilet
2. Flush to drain the tank
3. Unhook the old flapper from the overflow tube ears, disconnect the chain
4. Snap on the new flapper, reconnect the chain with ½ inch of slack
5. Turn water back on, let tank fill, test

Fix 2: Replace the Fill Valve

👉 Fill valve and flapper repair kit — replace both for a complete fix

1. Turn off water supply, flush, sponge out remaining water
2. Disconnect the supply line from the bottom of the tank
3. Unscrew the fill valve locknut from below (counterclockwise)
4. Remove old fill valve, insert new one, adjust height per instructions
5. Reconnect refill tube to overflow tube, reconnect supply line
6. Turn water on, let tank fill, adjust water level to 1 inch below overflow tube top

When Both Are Fine But Toilet Still Runs

If replacing the flapper and fill valve doesn't stop the running, check:

• Flush valve seat: The surface the flapper sits on may be warped or corroded. Run your finger around it — if it feels rough, the seat needs replacement or the entire flush valve assembly needs to be replaced.
• Tank cracks: Inspect the inside of the tank for hairline cracks that could be letting water escape.

Bottom Line

A toilet that won't stop running is almost always fixed by replacing the flapper, fill valve, or both. The complete repair kit covers both parts, takes 30 minutes, and stops the water waste immediately.