Troubleshooting a Toilet That Keeps Running (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, flush the toilet, and check the flapper or fill valve. Adjust or replace parts as needed to stop the continuous water flow.

Confirm the symptom

Water runs continuously after flushing
Toilet makes gurgling or hissing sounds
High water bill despite low usage
Tank refills frequently without flushing

Tools and prep

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

Step-by-step troubleshooting

Turn Off Water Supply
Do: Locate and turn the shut-off valve clockwise to stop water flow.
Observe: Water stops entering the tank.
Means: You can safely work on the toilet without flooding.
Next: Step 2
Flush and Inspect
Do: Flush the toilet and observe the tank and bowl.
Observe: Water level in the tank and movement of the flapper or fill valve.
Means: Identifies if the issue is with the flapper, fill valve, or water level.
Next: Step 3
Check Flapper Seal
Do: Lift the flapper manually and check for wear or debris.
Observe: Flapper closes tightly when released.
Means: A worn or dirty flapper may not seal properly, causing water to leak.
Next: Step 4
Adjust or Replace Flapper
Do: Adjust the chain length or replace the flapper if it doesn't seal.
Observe: Flapper closes completely without sticking.
Means: Improves the seal and stops water from leaking into the bowl.
Next: Step 5
Inspect Fill Valve
Do: Check the fill valve for proper operation and water level.
Observe: Fill valve shuts off when the tank is full.
Means: A faulty fill valve can cause overfilling and continuous water flow.
Next: Step 6
Adjust or Replace Fill Valve
Do: Adjust the float or replace the fill valve if it doesn't shut off properly.
Observe: Water stops at the correct level in the tank.
Means: Corrects overfilling and stops the toilet from running.
Next: Step 7
Test the Toilet
Do: Turn the water supply back on and flush the toilet.
Observe: Toilet fills and stops without running.
Means: The issue is resolved and the toilet functions properly.
Next: Complete

Common causes

Cause	Likelihood	Difficulty	Part often needed
Worn or damaged flapper The flapper doesn't seal properly, allowing water to leak into the bowl.	Common	Easy	Toilet flapper
Incorrect chain tension A too-tight or too-loose chain can prevent the flapper from closing fully.	Common	Easy	None
Faulty fill valve The fill valve doesn't shut off when the tank is full, causing overfilling.	Common	Easy–Medium	Fill valve
High water level in the tank Water overflows into the overflow tube, causing continuous running.	Sometimes	Easy	None
Clogged or dirty flapper seat Debris on the flapper seat prevents a tight seal.	Sometimes	Easy	Toilet flapper
Worn internal components Internal parts like the float or ballcock may wear out over time.	Sometimes	Medium	Fill valve or float assembly
Improperly adjusted float The float is set too high, causing the tank to overfill.	Sometimes	Easy	None
Leaking toilet bowl Cracks or gaps in the bowl allow water to escape continuously.	Rare	Hard	Toilet bowl or wax ring

Parts matching

Common parts needed to fix a running toilet:

Toilet flapper: $5–$15
Fill valve: $20–$40
Adjustable wrench: $10–$30
Plumber's putty: $5–$10
Replacement wax ring: $5–$10

Purchase parts compatible with your toilet model for the best results.

When to call a professional

The toilet continues to run after replacing the flapper and fill valve
You notice water leaking from the base of the toilet
The toilet tank cracks or breaks during repairs
You're unsure about the correct part or installation process
The issue persists despite multiple attempts to fix it

FAQ

How do I know if the flapper or fill valve is the problem?

If the flapper doesn't seal, water leaks into the bowl. If the fill valve doesn't shut off, the tank overflows. Check both to identify the issue.

Can I fix a running toilet without turning off the water?

No, always turn off the water supply to avoid flooding and make repairs easier.

How often should I replace the toilet flapper?

Replace the flapper every 1–2 years to prevent wear and leaks.

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

The issue might be with the fill valve or water level. Check these components next.

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

The fill valve may be faulty and need replacement.