Toilet Keeps Running After Flushed: How to Fix (Troubleshooting Guide)

On this page

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

Turn off the water supply and flush the toilet. Check the flapper for damage or misalignment. Adjust the float or replace the fill valve if the water level is too high. Replace the flapper if it doesn't seal properly.

Confirm the symptom

Water continues to run after flushing
Tank refills frequently without use
Gurgling or hissing sounds from the tank
High water bill with no obvious leaks

Tools and prep

Adjustable wrench
Screwdrivers (flathead and Phillips)
Plumber's putty or silicone sealant
Replacement flapper or fill valve
Bucket or towel
Turn off water supply valve behind the toilet
Wear rubber gloves to avoid contact with water and waste

Step-by-step troubleshooting

Turn Off Water Supply
Do: Locate and turn clockwise the shut-off valve behind the toilet base.
Observe: Water flow stops into the tank.
Means: You can safely work on the toilet without leaks.
Next: Flush the toilet to drain the tank.
Inspect the Flapper
Do: Check the flapper for cracks, warping, or mineral buildup.
Observe: Flapper doesn't seal tightly against the flush valve.
Means: A faulty flapper is causing the leak.
Next: Replace the flapper if damaged.
Adjust the Float
Do: Lower the float by bending the float arm or adjusting the clip on the fill valve.
Observe: Water level is about 1 inch below the overflow tube.
Means: The float was set too high, causing overfill.
Next: Test the toilet by flushing.
Check the Fill Valve
Do: Inspect the fill valve for wear or debris.
Observe: Water continues to leak into the overflow tube.
Means: The fill valve is faulty and needs replacement.
Next: Replace the fill valve.
Test the Toilet
Do: Turn the water supply back on and flush the toilet.
Observe: Tank fills and stops without running.
Means: The repair was successful.
Next: Monitor for 24 hours to ensure the issue is resolved.
Seal Leaks
Do: Apply plumber's putty or silicone sealant around the base if there are leaks.
Observe: Water no longer seeps from the base.
Means: The toilet is properly sealed.
Next: Final inspection for any remaining issues.

Common causes

Cause	Likelihood	Difficulty	Part often needed
Faulty Flapper The flapper doesn't seal properly, allowing water to leak into the bowl.	Common	Easy	Toilet flapper
High Water Level Water overflows into the overflow tube, causing continuous refilling.	Common	Easy	Float adjustment or fill valve
Worn Fill Valve The fill valve fails to shut off, leading to constant water flow.	Common	Easy–Medium	Fill valve
Mineral Buildup Calcium and lime deposits prevent the flapper or valve from closing properly.	Sometimes	Easy	Vinegar or descaling solution
Damaged Chain A chain that's too short or tangled prevents the flapper from closing fully.	Sometimes	Easy	Adjustable chain or new flapper
Faulty Float A stuck or damaged float can't regulate water level correctly.	Sometimes	Easy	Float or fill valve replacement
Worn Out Toilet Tank Components Aging parts like gaskets or seals can cause leaks and running water.	Rare	Medium	Toilet tank kit

Parts matching

Common parts needed for a running toilet fix:

Toilet Flapper: $5–$15
Fill Valve: $15–$30
Float Assembly: $10–$20
Adjustable Chain: $2–$5
Toilet Tank Kit: $20–$50
Plumber's Putty or Sealant: $3–$10

Purchase parts specific to your toilet model for the best fit.

When to call a professional

The toilet still runs after replacing all parts
You notice significant water damage or mold
You're unsure about the correct parts for your toilet model
The problem involves the wax ring or toilet base leaks
You hear gurgling from drains or other plumbing issues

FAQ

How do I know if the flapper is the problem?

If the flapper doesn't close tightly or shows cracks, it's likely the cause. Add food coloring to the tank and wait 30 minutes; if color appears in the bowl, the flapper is leaking.

Can a high water level really cause the toilet to run?

Yes. If the water level is above the overflow tube, it will continuously refill. Adjust the float to keep the level 1 inch below the overflow.

How often should I replace the flapper?

Replace the flapper every 1–2 years to prevent wear and leaks. Check it if you notice running water or frequent refilling.

What if adjusting the float doesn't work?

If the float is stuck or damaged, replace it or the entire fill valve. Some modern toilets use ballcock valves that require specific adjustments.

Is it normal for the toilet to make noise after fixing?

Some gurgling or hissing is normal as air escapes, but constant noise means a leak or misalignment. Double-check all connections and parts.