A toilet that starts running every few minutes—even when nobody has used it—is usually losing a small amount of water from the tank. As the tank level drops, the fill valve switches on briefly to replace that water. This cycle is often called “ghost flushing,” and while it may sound minor, it can waste a surprising amount of water over time.
The most likely cause: a leaking flapper
The rubber flapper at the bottom of the tank is supposed to create a watertight seal after each flush. If it is warped, dirty, brittle, or poorly aligned, water can slowly leak into the bowl. Once enough water leaves the tank, the fill valve turns on for a few seconds.
Remove the tank lid and watch the water level without flushing. If the toilet suddenly refills after several minutes, an internal leak is likely. A simple test is to place a few drops of food coloring in the tank and wait about 15–20 minutes without flushing. If colored water appears in the bowl, water is passing through the flush valve area.
Check the flapper chain
A chain that is too tight can hold the flapper slightly open. A chain that is excessively loose can become trapped underneath it. Ideally, the chain should have a little slack when the flapper is closed. Make sure it moves freely and is not catching on another tank component.
The water level may be too high
If the tank water rises high enough to spill into the overflow tube, the toilet can run intermittently or continuously. The normal water line should sit below the top of the overflow tube. Many fill valves have an adjustment screw or float that lets you lower the shutoff level.
Could the fill valve be failing?
A worn or dirty fill valve may fail to shut off consistently. If the flapper seals correctly and water is not entering the overflow tube, listen closely to the fill valve. Hissing, irregular refilling, or a valve that continues to pass water can point to a fill-valve problem.
What you can safely check yourself
- Confirm that the flapper closes completely.
- Check that the chain has slight slack and cannot become trapped.
- Look for mineral buildup around the flush-valve seat.
- Verify that the tank water level stays below the overflow tube.
- Use the food-coloring test to identify a slow tank-to-bowl leak.
When to call a plumber
Most intermittent running problems are inexpensive toilet-tank repairs. However, professional help makes sense if replacing or adjusting the obvious tank components does not stop the problem, if the shutoff valve is seized or leaking, or if you notice water around the base of the toilet. Water outside the fixture can indicate a different issue that should not be ignored.
Related: Why Is My Toilet Water Level Suddenly Low?
Bottom line
If your toilet runs every few minutes, start by looking for a slow leak from the tank into the bowl. The flapper, chain, water level, and fill valve are the most useful places to check. Fixing the cause early can stop the noise and prevent unnecessary water waste.