Stop a toilet that keeps running
Find the usual culprit and quiet the tank without replacing the whole toilet.
Home · 20–35 min · Easy
Before you start
Before removing parts, close the toilet supply using the valve's normal closing motion; valve designs differ, so do not assume every handle closes by repeated clockwise turns. If the valve will not move normally or begins leaking at the stem or connection, do not force it—stop and address the valve first.
Tools and materials
- Towel and soft nonabrasive cloth
- Sponge
- Food coloring or leak-detection dye
- Replacement flapper if needed
Check the problem
Find where the water is going
Remove the tank lid and watch a complete refill without touching the controls. Tank water spilling over the overflow-tube rim after the fill valve should have stopped points to a fill-level or fill-valve problem. Water delivered into the tube by the clipped refill hose during a normal refill does not. A no-flush dye test can distinguish a tank-to-bowl seal leak.
Run a flapper leak test
Add a few drops of food coloring to the tank and wait 10 minutes without flushing. Color in the bowl indicates a leak past the flapper or another flush-valve seal; it does not identify the exact failed part. Flush afterward to prevent staining.
Check the float and chain
The float should move freely and the chain should have the slack specified for the installed flapper. A stuck float or tangled chain is an observable fault. Tank water reaching or spilling over the overflow rim after refill supports a fill-level or fill-valve problem, but the exact valve instructions still control the correction.
Steps
Remove the lid and watch a refill
Lift the tank lid with both hands and set it on a towel. Flush once and watch the chain, flapper, float, refill tube, and water level through a complete cycle.
Free the handle and chain
Confirm the handle arm moves freely and the chain is not tangled, caught under the flapper, or pulled tight. Correct obvious interference before replacing parts.
Test for a tank-to-bowl leak
If tank water is spilling over the overflow rim, go to step 7 first; dye cannot isolate a seal leak while water is overflowing. Otherwise, add a few drops of food coloring to the tank and wait 10 minutes without flushing. Color in the bowl indicates a tank-to-bowl leak, not proof that the flapper alone is faulty. Flush afterward to prevent staining. Continue to steps 4–6 only for a suspected flapper or seat leak; otherwise go to step 7.
Shut off and drain the tank
Close the toilet supply using the valve's normal closing motion, flush, and hold the handle down. Remove residual tank water with a sponge so the flapper seat is easy to inspect.
Clean the seat or replace the flapper
Wipe mineral film from the flush-valve seat with a nonabrasive cloth. If the flapper is warped, brittle, or still leaks, unhook it and install an exact-size or manufacturer-approved replacement. If the seat or flush-valve body is cracked, badly pitted, or loose, stop: replacing the complete flush valve is outside this guide.
Set the chain slack
Connect the flapper chain to the flush-handle lever, not the fill valve or refill tube. With the flapper closed, set the slack specified by its manufacturer. Operate the handle: the flapper must lift fully and settle closed without excess chain catching underneath. Do not use a universal link count.
Correct the tank water level
If the level is already correct, leave the adjustment alone. Otherwise, follow the installed valve’s adjustment instructions, including whether to shut off water first. Reopen the supply if closed and observe a complete refill: water should stop at the tank or valve mark, or the level specified in its instructions. Keep the refill tube attached as specified, never submerged or pushed down the overflow tube. If the valve still will not stop filling, close the supply normally and arrange fill-valve service; replacement is outside this guide. The pictured refill arrangement is one example.
Restore water and test twice
Open the shutoff slowly if it is still closed. Flush twice and watch each complete refill: the flapper must seat and water must stop at the correct level, with no external leaks. Repeat the 10-minute no-flush dye test, then flush out the dye. If color still reaches the bowl or filling continues, the repair is not complete; close the supply normally and arrange further repair. Replace the lid only after the checks pass.
Two complete cycles stop at the specified level with the flapper seated and no continued bowl flow.
Tips
Take the old flapper with you
Flappers vary by diameter, hinge style, and valve design. Matching the original part is more reliable than choosing by appearance alone.
Match size and attachment style—not just color.
Use the flapper maker’s chain setting
A chain pulled tight can hold the flapper open; too much slack can catch beneath it. Use the installed flapper's specified slack rather than a universal link count.
The chain should lift cleanly without tugging at rest or falling under the flapper.
Use the manufacturer’s fill reference
Set the finished water level at the tank or fill-valve mark. If no mark is present, use the toilet and fill-valve instructions to establish the required clearance below the overflow tube and the correct refill-tube attachment.
Do not substitute a generic dimension or universal tube arrangement for the actual instructions.
Test with the lid still off
Run two complete flush-and-refill cycles while every moving part is visible, then repeat the dye test before replacing the lid.
Verify the seal and shutoff—not merely that the noise stopped.