Toilet Won’t Stop Running? Here’s How to Fix It (and Why It Happens)
Reading Time: 6minutes
Published February 25, 2025 | Updated May 11, 2026
If your toilet won’t stop running after you flush, the problem is usually the flapper, chain, float, or fill valve inside the tank. Most of the time, you can figure out which part is causing the problem in about 5 minutes just by removing the tank lid and watching what happens after the flush. In many cases, the repair costs less than $10 and only requires a basic replacement part from a hardware store.
Need Help Fixing a Running Toilet?
Aaron Services provides same-day plumbing service across North Atlanta for toilets that won’t stop running, leaking toilets, shutoff valve problems, and other plumbing repairs.
After the toilet flushes and starts refilling, press down gently on the rubber flapper inside the tank.
If the running stops after pressing the flapper down, the flapper usually is not sealing correctly and likely needs replacement.
That single test solves a huge percentage of running toilet calls.
How to Stop a Toilet From Running
A toilet that keeps running after flushing often has a slow flapper leak or improperly adjusted float. Here’s how you can try to fix a running toilet yourself:
Step 1: Turn Off the Water Supply
Locate the shutoff valve behind the toilet near the floor and turn it clockwise until it stops.
If the valve will not fully shut off the water, do not force it aggressively. Older shutoff valves can break or begin leaking when turned after years of sitting unused.
Step 2: Flush the Toilet
Flush the toilet after shutting the water off.
This empties most of the water from the tank so you can see the internal parts more clearly and work inside the tank without water constantly refilling.
If the toilet tank begins refilling even after the shutoff valve is turned off, the shutoff valve may no longer be working correctly. That is usually a good reason to call a plumber, since it is important to be able to shut water off at plumbing fixtures during emergencies or future repairs.
Step 3: Remove the Tank Lid Carefully
Lift the toilet tank lid straight up and place it on a towel or soft surface nearby.
Toilet lids crack surprisingly easily, especially older porcelain ones.
Step 4: Check the Flapper
The flapper is the rubber piece at the bottom of the tank that lifts during a flush and then seals afterward.
Common problems include:
warped rubber
mineral buildup
chain holding it open
uneven sealing
After the toilet flushes and starts refilling, press down gently on the flapper.
If the running water stops, the flapper is usually the problem.
How to Replace a Toilet Flapper
Most flappers twist or unclip off the overflow tube inside the tank.
Take the old flapper with you to the hardware store so you can match the size and style. Most replacements cost around $5–10.
The chain connecting the handle to the flapper should have a little slack, but not enough to tangle.
If the chain is:
too tight → the flapper may not fully close
too loose → the chain may get caught underneath the flapper
Usually about 1/2 inch of slack works best.
Step 6: Check the Float and Fill Valve
If the flapper looks fine, the next thing to check is the float.
The float controls the water level inside the tank. If it is set too high, water keeps flowing into the overflow tube and the toilet runs continuously.
Lower the float slightly and test the toilet again.
If your toilet keeps running after replacing the flapper, the fill valve may be the real issue.
A common replacement is the Fluidmaster 400A, which is one of the most commonly used residential fill valves.
Why Won’t My Toilet Stop Running?
Worn or Warped Flapper
This is the most common cause by far.
Rubber flappers slowly warp over time from chlorine, hard water, and constant use. Once they stop sealing correctly, water leaks into the bowl continuously.
We see this constantly in older North Atlanta homes where the original toilet parts have never been replaced.
Float Set Too High
If the tank water level rises above the overflow tube, water keeps draining into the bowl and the fill valve never shuts off completely.
Sometimes homeowners accidentally bump the float while cleaning inside the tank.
Faulty Fill Valve
Fill valves wear out over time.
Common signs include:
hissing sounds
intermittent running
inconsistent refill speed
water spraying inside the tank
If adjusting the float does not solve the problem, the fill valve is often next.
Tangled or Misadjusted Chain
Chains sometimes get caught underneath the flapper or become tangled after repairs.
Even a slightly lifted flapper can keep the toilet running nonstop.
High Water Pressure
Sometimes the toilet itself is not the real problem.
Excessively high water pressure can cause fill valves to fail faster and may create repeated running toilet issues throughout the home.
If toilets, faucets, or appliances seem to have recurring valve problems, it may be worth checking your home’s water pressure.
How to Test If Your Toilet Is Silently Running
Some toilets run constantly. Others leak quietly enough that homeowners do not notice for weeks.
A simple dye test helps confirm it.
This simple test can help you determine whether your toilet is running
Put a few drops of food coloring into the toilet tank.
Wait 15–20 minutes without flushing.
If colored water appears in the bowl, the flapper is leaking.
This test is especially useful if your water bill suddenly increases without an obvious reason.
How Much Water Does a Running Toilet Waste?
A running toilet can waste thousands of gallons of water every month.
In some cases:
150–200 gallons per day
more than 6,000 gallons per month
noticeably higher water bills
Many homeowners don’t realize how expensive a small toilet leak can become until the next water bill arrives. You can see how much a running toilet can increase your water bill using our leak calculator.
I Replaced Everything and My Toilet Still Won’t Stop Running
Sometimes a toilet continues running even after replacing the flapper, fill valve, and other internal parts.
At that point, the problem may be:
an older or discontinued toilet model
worn mounting surfaces inside the tank
cracks around the overflow tube
mismatched replacement parts
poor-quality internal components
In some older builder-grade toilets, the internal parts wear unevenly over time and repairs become less reliable.
If the toilet is 15–20 years old and continues having problems after multiple repairs, replacement may be the more practical long-term solution.
Higher-quality toilets from manufacturers like American Standard and Toto generally use more durable internal components and replacement parts that remain easier to find over time.
Still Have a Toilet That Won’t Stop Running?
Aaron Services provides same-day plumbing service across North Atlanta, including Cumming, Lawrenceville, Roswell, Alpharetta, Suwanee, Johns Creek, Buford, and surrounding areas.
Usually because the flapper is leaking, the float is too high, the chain is tangled, or the fill valve is failing. Most running toilets can be diagnosed by removing the tank lid and watching what happens after the flush.
How do I stop a toilet from running?
Start by checking the flapper. If pressing down gently on the flapper stops the running water, the flapper usually needs replacement. If that does not solve the problem, check the chain, float, and fill valve.
Can a running toilet fix itself?
No. In most cases, the problem gradually gets worse over time and wastes more water.
How much does it cost to fix a running toilet?
DIY repairs are often under $10–20 for simple parts like flappers or chains. Professional repairs commonly range from about $175–350 depending on what is failing.
Is a running toilet an emergency?
Usually not a safety emergency, but it can waste a significant amount of water and increase your water bill quickly.
How long can a toilet run before it causes damage?
Some toilets can run for months without visible damage, but hidden leaks and constant overflow can eventually create flooring damage, high water bills, or excessive wear on internal components.
An Extra Plumbing Tip
If you find yourself replacing toilet flappers frequently or dealing with toilets that keep running after repairs, cleaning tablets inside the toilet tank may be part of the problem.
Those tablets do not just break down stains and buildup — they also slowly damage the rubber parts inside the tank, including flappers and gaskets. We see this fairly often in homes where the tablets are used continuously.
While the tablets may save a little cleaning time, they can shorten the lifespan of the toilet’s internal parts and lead to more repairs over time.
