My Toilet Keeps Running How to Fix (Troubleshooting Guide)

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Quick answer
Confirm the symptom
Tools and prep
Step-by-step troubleshooting
Common causes table
Parts matching
When to call a pro
FAQ
Related guides

Quick answer

A running toilet is usually caused by a faulty flapper or fill valve. Turn off the water supply, inspect the flapper chain, and adjust or replace as needed. Check the fill valve height and float setting to stop continuous water flow.

Confirm the symptom

Toilet continues to run after flushing
Water is constantly flowing into the overflow tube
You hear a hissing or trickling sound from the tank

Tools and prep

Adjustable wrench
Screwdrivers (flathead and Phillips)
Replacement flapper or fill valve
Plumber's putty or sealant
Turn off water supply to the toilet
Allow tank to empty completely before starting

Step-by-step troubleshooting

Inspect the Flapper
Do: Lift the tank lid and flush the toilet. Watch the flapper to see if it seals properly after the tank empties.
Observe: Flapper does not close fully or is damaged
Means: Flapper is faulty or chain is too tight/loose
Next: Adjust or replace the flapper
Adjust the Flapper Chain
Do: Check the chain connecting the flapper to the flush handle. Ensure it has 1/2 inch of slack.
Observe: Chain is too tight or too loose
Means: Improper tension prevents the flapper from sealing
Next: Adjust the chain length
Check the Fill Valve
Do: Look at the fill valve to see if it's set too high, causing water to spill into the overflow tube.
Observe: Water level is above the overflow tube or fill valve is malfunctioning
Means: Fill valve needs adjustment or replacement
Next: Adjust or replace the fill valve
Inspect the Float
Do: Check the float mechanism to ensure it's not stuck or set too high.
Observe: Float is stuck or water level is too high
Means: Float is misadjusted or faulty
Next: Adjust or replace the float
Test the Toilet
Do: Turn the water supply back on and let the tank fill. Flush the toilet and observe for continuous running.
Observe: Toilet runs continuously or water level is incorrect
Means: Further adjustments or part replacements are needed
Next: Repeat steps or replace additional parts
Seal Leaks
Do: Check for leaks around the base of the toilet and at the tank-to-bowl connection.
Observe: Water pooling or dampness around the toilet
Means: Leak is present and needs sealing
Next: Apply plumber's putty or call a professional

Common causes

Cause	Likelihood	Difficulty	Part often needed
Faulty Flapper The rubber seal doesn't close properly, allowing water to leak into the bowl.	Common	Easy	Toilet flapper
Misadjusted Chain A chain that's too tight or too loose prevents the flapper from sealing correctly.	Common	Easy	None
High Water Level Water level set too high causes overflow into the tube, triggering continuous refill.	Common	Easy	Fill valve adjustment
Faulty Fill Valve The fill valve may be worn or damaged, causing it to run continuously.	Sometimes	Easy–Medium	Fill valve
Stuck or Faulty Float A faulty float can't shut off the water supply, leading to overfilling.	Sometimes	Easy	Float or fill valve
Worn-Out Components Over time, parts like the flapper or fill valve can wear out and need replacement.	Sometimes	Easy–Medium	Toilet flapper or fill valve
Leak at Base A leak at the base of the toilet can cause water to continuously run and waste water.	Rare	Hard	Toilet wax ring or professional repair

Parts matching

Common parts needed to fix a running toilet include:

Toilet flapper
Fill valve
Float assembly
Plumber's putty
Adjustment screws for fill valve

Purchase parts that match your toilet model for compatibility and proper function.

When to call a professional

The toilet continues to run after replacing all accessible parts
You notice significant water damage or mold around the toilet
You're unsure about the correct part for your toilet model
The base of the toilet is leaking and you can't stop the leak
You hear unusual noises like gurgling or hammering after repairs

FAQ

How do I know if my flapper is faulty?

If the flapper doesn't close fully after flushing or shows signs of wear, it likely needs replacement.

Can I adjust the fill valve myself?

Yes, most fill valves can be adjusted using the adjustment screw on the valve. If it's damaged, replace it with a new one.

Why is my toilet running even after I fixed the flapper?

Another issue, such as a faulty fill valve or high water level, might still be causing the problem. Check those components next.

How often should I replace my toilet flapper?

Flappers typically last 1–5 years. Replace if you notice leaks or the toilet runs continuously.

What if adjusting the float doesn't stop the running?

The float may be damaged. Try replacing it or the entire fill valve assembly.