Why is my toilet running constantly after flushing?

A toilet that runs continuously is usually caused by a worn flapper, a faulty fill valve, or a chain that's too tight. This guide will help you stop the phantom flushing.

Category:Plumbing

Difficulty:Easy

Time:15 min

Success:50%

Updated:Jul 6, 2026

quick_referenceQuick Answer

For Why is my toilet running constantly after flushing?, start with "Check and replace the flapper": Turn off the water supply valve behind the toilet. Flush to empty the tank. Unhook the old flapper from the flush lever and overflow tube. Install a new universal flapper, ensuring the chain has about 1/2 inch of slack. Turn the water back on and test. Stop DIY if water is leaking from the base of the toilet onto the floor. This is listed as a easy recovery and usually takes about 15 min.

verifiedGuide Snapshot

Repair areaPlumbing

Estimated time15 min

DifficultyEasy

Stop conditions3

Last updated Jul 6, 2026. Review the stop conditions before continuing.

account_treeRecovery State

DeviceToilet

Current stateRunning

Specific stateContinuous Fill

Failed stepFlapper Wear

Likely failure typeWorn Part

DIY boundaryDIY recovery first

paymentsCost decision

help1. Understand the Problem

A running toilet wastes water and can drive up your utility bill. The most common cause is a flapper that doesn't seal properly, allowing water to leak from the tank into the bowl. A misadjusted fill valve or a float that's set too high can also cause continuous running. This guide covers the three most common fixes.

build_circle2. Try This First

Best First Step

Check and replace the flapper

Turn off the water supply valve behind the toilet. Flush to empty the tank. Unhook the old flapper from the flush lever and overflow tube. Install a new universal flapper, ensuring the chain has about 1/2 inch of slack. Turn the water back on and test.

visibility3. Visual Guidance

See what's happening and how to try the first recovery step.

Check and replace the flapperTurn off the water supply valve behind the toilet. Flush to empty the tank. Unhook the old flapper from the flush lever and overflow tube. Install a new universal flapper, ensuring the chain has about 1/2 inch of slack. Turn the water back on and test.

Adjust the float levelIf the water runs into the overflow tube, the float may be set too high. On a float cup fill valve, pinch the spring clip and slide the float down. On an old ball float, bend the float arm down slightly. The water level should be about 1 inch below the top of the overflow tube.

Clean the fill valveIf the fill valve hisses or doesn't shut off fully, it may have debris. Turn off the water. Remove the fill valve cap and clean the internal diaphragm with a toothbrush and vinegar. Reassemble and test.

Check the chain lengthIf the chain is too tight, it can lift the flapper slightly, causing a leak. Adjust the chain so it has about 1/2 inch of slack when the flapper is closed. Cut off any excess chain.

autorenew4. If That Doesn't Work

Try the next recovery options.

Replace the fill valveIf adjusting the float doesn't stop the running, the fill valve may be worn. Install a universal replacement fill valve following the instructions.

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Frequently Asked Questions

How do I know if the flapper is bad?expand_more

Drop a few drops of food coloring into the tank. Wait 15 minutes without flushing. If the colored water appears in the bowl, the flapper is leaking and needs replacement.

Why does my toilet run intermittently?expand_more

Intermittent running is often caused by a slow leak from a worn flapper or a fill valve that occasionally sticks. The tank slowly loses water, then refills.

Can a running toilet increase my water bill?expand_more

Yes, a running toilet can waste up to 200 gallons of water per day, significantly increasing your water bill. Fix it as soon as possible.

What if the water level is too high?expand_more

If the water level is above the overflow tube, water will constantly trickle into the bowl. Adjust the float lower so the water stops about 1 inch below the tube top.