How-to
How to Fix a Running Toilet in 15 Minutes
🇩🇪 Diesen Artikel auf Deutsch lesenA running toilet is almost always caused by a worn flapper, a misadjusted float or a faulty fill valve. Test the flapper with a few drops of food coloring in the tank: if the color appears in the bowl without flushing, replace the flapper. If water runs into the overflow tube, lower the float.
A running toilet is more than an annoying sound. A badly leaking toilet can waste up to around 200 gallons of water a day, which shows up quickly on your water bill. The good news: the parts inside a toilet tank are simple, cheap and standardized.
How a toilet tank works
When you flush, the flapper at the bottom of the tank lifts and water rushes into the bowl. The flapper drops back, and the fill valve refills the tank until the float rises and shuts it off. If water keeps flowing, one of those three parts is not doing its job.
Step by step
- Do the dye test
Add a few drops of food coloring to the tank and wait 15 minutes without flushing. If color shows up in the bowl, the flapper leaks.
- Check the water level
Remove the tank lid. The water should stop about an inch below the top of the overflow tube. If it flows into the tube, the float is set too high.
- Adjust the float
On modern fill valves, turn the adjustment screw or slide the clip to lower the float cup. On older ball floats, gently bend the arm down.
- Replace the flapper
Turn off the water at the valve behind the toilet and flush to empty the tank. Unhook the chain and the flapper ears, clip on the new flapper and reattach the chain with a little slack.
- Replace the fill valve if needed
If the fill valve still runs, turn off the water, empty the tank, disconnect the supply line under the tank, unscrew the lock nut and install the new valve following the package instructions.
- Test
Turn the water back on, let the tank fill and repeat the dye test to confirm the leak is gone.
Which part do you need?
| Symptom | Likely cause | Fix |
|---|---|---|
| Color appears in the bowl during dye test | Worn flapper | Replace flapper ($5–$15) |
| Water flows into the overflow tube | Float set too high | Lower the float |
| Hissing, tank refills on its own every few minutes | Flapper or fill valve | Replace flapper first, then fill valve |
| Tank fills very slowly or noisily | Worn fill valve | Replace fill valve ($10–$25) |
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Shower Cost CalculatorWater and energy cost of your showersTry the calculator →Frequently asked questions
Why does my toilet run for a few seconds by itself?
That is called 'phantom flushing' and usually means the flapper leaks slowly, so the tank refills now and then.
Do I need to turn off the water to adjust the float?
No, you can adjust the float with the water on. Turn it off before replacing parts.