Still running after flapper replacement

Fill valve not seating Replace fill valve; check for sediment in valve seat

Tank fills but water trickles into bowl

Flapper chain too short or kinked Lengthen chain to ½ in slack; ensure no kinks

Float adjustment slipping Tighten float screw; replace fill valve if adjustment won't hold

Slow flapper leak Replace flapper; clean flush valve seat; check for hairline cracks in overflow tube

Debris in fill valve Remove fill valve cap; rinse diaphragm under running water; reassemble

BathroomBeginner

Time

15–30 min

Steps

Pre-check

4 items

Skill

Beginner

Diagnose and stop a continuously running toilet by checking and repairing the flapper, fill valve, float, and overflow tube.

Read before starting

Turn off supply valve before replacing parts; tank water is clean but wipe spills promptly to avoid slips; avoid over-tightening plastic fittings.

4 items · complete before you start

Locate the supply valve behind the toilet base and confirm it turns
Required
Identify flush mechanism type: flapper-and-chain or canister seal
Required
Have replacement flapper or fill valve kit matching your toilet brand (universal fits most)
Towels and a small bucket or cup for residual tank water

0 / 32 complete

Remove tank lid; set on towel to protect
Listen: hissing = fill valve not shutting off; silent trickle = flapper not sealing
Add a few drops of food coloring to tank water; wait 10 min without flushing — if color appears in bowl, flapper is leaking
Check water level: if water is flowing into the overflow tube, the float or fill valve is the issue

Press flapper down with your finger while toilet is running
If running stops, flapper is warped or has mineral buildup
Inspect flapper for cracks, warping, or slime; feel the seating surface for roughness
Clean the flapper seat (rim of flush valve) with a cloth to remove deposits

Turn off supply valve clockwise; flush to empty tank
Sponge or cup out remaining water
Unhook old flapper ears from flush valve pegs
Hook new flapper onto same pegs; reconnect chain to handle lever
Set chain length: ½ in slack when flapper is closed — too tight prevents seal, too loose prevents full lift

If water level is above overflow tube, the float is set too high
Ball float: bend the rod down slightly, or turn the adjustment screw on top of the fill valve
Cup float: pinch the spring clip and slide the float down the rod
Target water level: ½–1 in below the top of the overflow tube (most tanks have a stamped line)

Turn off supply; flush and sponge tank dry
Disconnect supply line from bottom of tank (have bucket ready)
Unscrew locknut under tank; lift out old fill valve
Insert new fill valve; adjust height so overflow is 1 in below tank top per instructions
Hand-tighten locknut + ¼ turn with pliers (no more — plastic cracks)
Reconnect supply; attach refill tube to overflow with included clip

Open supply valve slowly
Let tank fill completely; water should stop on its own
Flush 3–4 times; confirm tank refills and stops each time
Re-check food coloring test to confirm flapper seal
Listen for 30 seconds of silence after fill — any hissing means further adjustment needed