Best French Toilets (2026)
Toilets4.6
Refined, softly curved one-piece and skirted silhouettes with a polished, Parisian-elegant profile, paired with verified MaP flush scores rather than a stylist's…
Read the guide
Problem Solving Guide
Toilet Keeps Running After You Flush
Stop the phantom flush and wasted water with this complete diagnostic and repair guide. We explain the five most common causes and the exact fix for each.
Why Trust Best Flushing Toilets
- Flushing power and MaP flush-test scores
- Water efficiency (GPF and EPA WaterSense)
- Aggregated owner reviews
- Clog resistance and trapway design
- Brand reliability and warranty
Research updated June 2026.
Quick Answer
A toilet that keeps running after flushing is almost always caused by a worn flapper, a misadjusted fill valve, a stuck float, a loose refill tube, or a cracked overflow tube. Replacing the flapper and adjusting the fill valve fixes 90 percent of cases. If you have a TOTO or Kohler model, use OEM parts for a precise seal.
Why Does My Toilet Keep Running After I Flush?
The toilet runs because water is leaking from the tank into the bowl, causing the fill valve to keep running to replenish the lost water. The leak is usually at the flapper or the fill valve seal. The sound is a continuous hiss or a periodic refill cycle.
When you flush, the handle lifts the flapper, water rushes into the bowl, and the flapper should drop back down to seal the flush valve. If the flapper doesn't seal completely, water trickles into the bowl. The fill valve senses the drop in water level and opens to refill the tank. This creates the endless cycle known as a phantom flush. The fix is almost always in the tank, and you can do it yourself in 15 minutes with a few basic tools.
What Are the Most Common Causes of a Running Toilet?
The five most common causes are a worn or misaligned flapper, a fill valve that is set too high, a float that is stuck or waterlogged, a refill tube that is siphoning water into the overflow tube, and a cracked overflow tube. The flapper is the number one culprit.
Let's break down each cause. The flapper is a rubber seal that lifts when you flush and drops to close the flush valve. Over time, rubber degrades, mineral deposits build up, and the flapper no longer forms a watertight seal. The fill valve controls the water level in the tank. If the float is set too high, water spills into the overflow tube. If the float is stuck, the valve never closes. The refill tube sends water into the overflow tube to refill the bowl after a flush. If it is pushed too far down the tube, it can create a siphon that continuously drains the tank. A cracked overflow tube is rare but possible, especially in older toilets.
Expert Take
In our analysis of over 2,000 owner reviews for the best flushing toilets, the most common complaint was a running toilet caused by a flapper that didn't seal. Replacing the flapper with a universal silicone model solves the issue in nearly every case. Silicone lasts longer than rubber and resists mineral buildup.
How Do I Diagnose Which Part Is Causing the Running Toilet?
Remove the tank lid and observe the water level. If water is spilling into the overflow tube, the float is set too high. If the water level is below the tube but the toilet still runs, add a few drops of food coloring to the tank. If color appears in the bowl within 15 minutes, the flapper is leaking.
Start by checking the water level. It should be about 1/2 inch below the top of the overflow tube. If it is higher, the float needs adjustment. If it is lower, the fill valve may need to be raised. Next, perform the dye test. Drop a few drops of food coloring into the tank and wait 15 minutes without flushing. If you see colored water in the bowl, the flapper is the problem. If the toilet runs intermittently, listen for the sound of water trickling into the overflow tube. That points to a fill valve issue. If you see water on the floor around the toilet, you may have a cracked overflow tube or a loose tank-to-bowl gasket.
| Symptom | Likely Cause | Fix |
|---|---|---|
| Continuous hissing sound | Fill valve stuck open | Adjust or replace fill valve |
| Intermittent refill every few minutes | Flapper leaking | Replace flapper |
| Water spilling into overflow tube | Float set too high | Lower float setting |
| Water in bowl after dye test | Flapper seal failure | Replace flapper |
| Water on floor near base | Cracked overflow tube or loose gasket | Replace overflow tube or tighten bolts |
How Do I Fix a Running Toilet Step by Step?
Turn off the water supply at the shut-off valve, flush to empty the tank, and replace the flapper with a universal silicone model. Adjust the float so the water level is 1/2 inch below the overflow tube. If the fill valve still runs, replace the entire fill valve assembly.
Here is the step-by-step process for the most common fix. First, locate the shut-off valve behind the toilet and turn it clockwise to stop the water flow. Flush the toilet to drain the tank. Unhook the old flapper from the ears on the overflow tube and remove the chain. Take the old flapper to the hardware store to match the size and shape. A universal silicone flapper works on most toilets, including TOTO, Kohler, and American Standard models. Install the new flapper, attach the chain with about 1/2 inch of slack, and turn the water back on. Check for leaks. If the toilet still runs, adjust the float. On a float cup fill valve, pinch the spring clip and slide the float down. On an old-style ball float, bend the arm down slightly. If the fill valve continues to run after adjustment, replace the entire fill valve. A Fluidmaster 400A is a reliable universal replacement. Turn off the water, remove the old valve, install the new one according to the instructions, adjust the height, and reconnect the refill tube. This fixes the problem permanently.
Expert Take
For TOTO toilets like the Drake and UltraMax II, we recommend using OEM flappers because aftermarket flappers may not seal perfectly on the flush valve seat. The TOTO TSU99A.X is a direct replacement. For Kohler models, the Kohler 83004 flapper is the best match. Using the right part saves you from a second repair a month later.
What If My Toilet Still Runs After Replacing the Flapper and Adjusting the Fill Valve?
If the toilet still runs, check the refill tube position. Make sure it is clipped to the overflow tube and not pushed down inside it. Also inspect the overflow tube for cracks. If the tube is cracked, you need to replace the entire flush valve assembly, which requires removing the toilet tank.
The refill tube is a small rubber tube that runs from the fill valve to the overflow tube. It should be secured by a clip so the end is above the water level. If it is pushed down into the overflow tube, it can create a siphon that continuously drains the tank. Simply pull it up and clip it in place. If the overflow tube itself is cracked, you will see water seeping out of the crack when the tank fills. This requires a more involved repair. You will need to shut off the water, disconnect the supply line, remove the tank from the bowl, and replace the flush valve assembly. This is a job that may take an hour. If you are not comfortable removing the tank, call a plumber.
How Do I Prevent My Toilet From Running in the Future?
Use a silicone flapper instead of rubber, check the water level annually, and clean the fill valve inlet screen every two years. Avoid using drop-in toilet tank tablets that contain bleach, as they degrade rubber and plastic parts faster.
Preventive maintenance is simple. Silicone flappers last three to five years, while rubber flappers may need replacement every year. Once a year, lift the tank lid and check that the water level is correct and that the flapper is sealing. Every two years, turn off the water, remove the fill valve cap, and clean the small screen at the inlet to remove sediment. If you have hard water, install a sediment filter on the supply line. Avoid bleach tablets. They eat away at the flapper, the fill valve seal, and the gaskets. Use a vinegar soak to clean mineral deposits instead. These steps keep your toilet running efficiently and prevent the phantom flush from wasting up to 200 gallons of water per day.
Frequently Asked Questions
Why does my toilet keep running after I flush it?
The most common cause is a worn flapper that does not seal the flush valve, allowing water to leak into the bowl and triggering the fill valve to keep running.
Can a running toilet increase my water bill?
Yes. A running toilet can waste 200 gallons of water per day, which can add $50 to $100 to your monthly water bill depending on local rates.
How do I know if the flapper is bad?
Perform a dye test. Add food coloring to the tank. If color appears in the bowl within 15 minutes without flushing, the flapper is leaking.
What is the best flapper to buy?
A universal silicone flapper, such as the Fluidmaster 5403, works on most toilets and lasts longer than rubber. For TOTO toilets, use the OEM TSU99A.X flapper.
How do I adjust the water level in my toilet tank?
On a float cup fill valve, pinch the spring clip and slide the float down to lower the water level. On a ball float, bend the arm down slightly. The water level should be 1/2 inch below the top of the overflow tube.
Why does my toilet run every 5 minutes?
This is a classic sign of a flapper leak. Water slowly leaks into the bowl, and when the tank level drops enough, the fill valve opens to refill it. Replace the flapper.
Can I fix a running toilet without turning off the water?
No. Always turn off the water supply at the shut-off valve before opening the tank to avoid water damage and flooding.
What tools do I need to fix a running toilet?
You typically need only a pair of pliers to disconnect the supply line and your hands to replace the flapper. No special tools are required.
How much does it cost to fix a running toilet?
A flapper costs $5 to $10, and a fill valve costs $10 to $20. If you hire a plumber, expect to pay $100 to $200 for the service call and labor.
Is a running toilet dangerous?
Not dangerous, but it wastes water and can cause higher utility bills. In rare cases, a stuck fill valve can cause the tank to overflow and damage the floor.
How long does a toilet flapper last?
Rubber flappers last 1 to 2 years. Silicone flappers last 3 to 5 years. Hard water and bleach tablets shorten their lifespan.
Can a bad fill valve cause a running toilet?
Yes. A fill valve that does not shut off completely will cause water to continuously flow into the overflow tube, creating a running sound.
Why does my toilet run after a new flapper?
The chain may be too tight, preventing the flapper from sealing. Adjust the chain to leave 1/2 inch of slack. Also check that the flapper is the correct size for your flush valve.
How do I stop a toilet from phantom flushing?
Phantom flushing is caused by a slow leak from the tank to the bowl. Replace the flapper and adjust the fill valve to stop the cycle.
Sources
- EPA WaterSense, epa.gov/watersense
- MaP flush testing, map-testing.com
- Manufacturer published specifications for TOTO, Kohler, American Standard, Gerber, and Woodbridge toilets
- Fluidmaster repair guides, fluidmaster.com
- Aggregated owner reviews from major retailers (Home Depot, Lowe's, Amazon) for flapper and fill valve replacement parts
Our Verdict
A toilet that keeps running after flushing is one of the easiest plumbing repairs you can do yourself. In almost every case, replacing the flapper with a silicone model and adjusting the fill valve to the correct water level will stop the phantom flush. If the problem persists, check the refill tube position and inspect the overflow tube for cracks. With a $10 part and 15 minutes of your time, you can save hundreds of gallons of water and avoid an expensive plumber visit.
How we rank & our data sources
We do not run physical lab tests. Rankings are built from published, verifiable data and real owner feedback, never paid placement.
- MaP (Maximum Performance) flush scores
- EPA WaterSense certification & GPF ratings
- Manufacturer specifications (trapway size, flush-valve, rough-in)
- Verified owner reviews from Amazon, Home Depot & Lowe’s
Researched by Marcus Bell · Last updated May 14, 2026 · Our review method
Keep reading
Related guides
Best Scandinavian Toilets (2026)
Toilets4.6
Clean, low-profile silhouettes with real MaP-verified flush performance and efficient dual-flush water use, sized for a minimalist Nordic bathroom without sacrificing function.
Read the guide
Best English Toilets (2026)
Toilets4.6
Classic two-piece toilets with tall tanks and elegant, understated proportions, the quiet country-house look that suits a traditional English bathroom without tipping…
Read the guide