How to Stop a Running Toilet

Step-by-Step

1. 1

   Step 1: Take Off the Tank Lid and Watch a Flush

   Lift the ceramic tank lid straight up and set it flat on a folded towel. Flush once and watch the tank refill so you can see where water is escaping.

   Pro tip

   Setting the lid flat on the floor rather than upright keeps it from tipping and cracking.

   Watch out

   Tank lids are heavy and brittle. Use both hands.
2. 2

   Step 2: Identify Which Kind of Running You Have

   If water trickles into the bowl between flushes, the flapper is leaking. If water runs continuously into the overflow tube, the water level is too high or the fill valve is not shutting off.

   Pro tip

   A dye test settles it: add food coloring to the tank, wait 15 minutes without flushing, and check the bowl for color.
3. 3

   Step 3: Check the Flapper Chain

   Look at the chain between the flush lever and the flapper. It should have a small amount of slack — enough to let the flapper seal completely, but not so much that it slips under the flapper and holds it open.

   Pro tip

   Move the chain one link at a time and test after each change.
4. 4

   Step 4: Inspect and Clean the Flapper Seat

   Press the flapper down with a finger and see whether the running stops. Wipe the flapper and the seat it rests on to remove mineral buildup or grit that could break the seal.

   Pro tip

   If the flapper feels stiff, warped, or brittle, it likely needs replacing.

   Watch out

   Shut off the supply valve before removing the flapper.
5. 5

   Step 5: Set the Water Level Correctly

   Adjust the float so the tank stops filling slightly below the top of the overflow tube, or at the fill line marked by the manufacturer. Depending on the valve, this is a screw, a clip on a rod, or a sliding collar.

   Pro tip

   If water is spilling into the overflow tube, the level is too high no matter how the toilet was set originally.
6. 6

   Step 6: Test the Fill Valve

   Flush and watch the fill valve. It should refill the tank and shut off cleanly. If it keeps hissing or cycling on and off after the level is set correctly, the fill valve is worn and should be replaced.

   Pro tip

   Note the brand printed on the valve before shopping for a replacement.
7. 7

   Step 7: Replace Only the Failing Part

   If adjustment did not solve it, shut off the supply valve, flush to empty the tank, and replace the specific part that failed — usually the flapper or the fill valve. Match the replacement to your toilet model.

   Pro tip

   Bring the old part to the store; flappers and valves are not universal.

   Watch out

   If the shutoff valve is stuck, corroded, or leaking, stop and call a plumber.
8. 8

   Step 8: Reassemble and Confirm It Holds

   Turn the water back on, let the tank fill, and watch for several minutes with the lid off. Confirm no water is entering the bowl or the overflow tube, then replace the lid.

   Pro tip

   Check again a few hours later — slow leaks can take time to show.

Tips

• Set the tank water level slightly below the top of the overflow tube, or to the fill line marked by the manufacturer.
• Add a few drops of food coloring to the tank and wait without flushing: color appearing in the bowl means the flapper is leaking.
• Take a photo of the parts before removing anything so reassembly is straightforward.
• Bring the old part with you when buying a replacement, since flappers and valves are not universal.

Common Mistakes

• Replacing parts before identifying which one is failing.
• Leaving the chain so long it slips under the flapper, or so short the flapper cannot close.
• Setting the water level above the overflow tube, which guarantees continuous running.
• Forcing a corroded supply shutoff valve instead of stopping and calling a plumber.

Frequently Asked Questions

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