If your toilet keeps refilling and won’t stop, it can be frustrating and noisy. You may hear constant running water or a steady stream flowing inside the tank.
The good news is that this problem is usually caused by one of a few small parts inside the tank. Most fixes take less than 30 minutes and cost under $25.
Let’s walk through the most common causes and what to check first.
Why a Toilet Won’t Stop Refilling
A toilet refills after every flush to restore water to the tank and bowl. When it doesn’t stop, it means water is either:
• Escaping from the tank
• Flowing into the overflow tube
• Not triggering the fill valve to shut off
The issue is almost always inside the tank.
Start here.
- Check If Water Is Flowing Into the Overflow Tube
Remove the tank lid and look at the overflow tube (the vertical pipe in the center of the tank).
If water is constantly spilling into that tube, your tank water level is set too high or the fill valve isn’t shutting off properly.
How to fix it:
Locate the fill valve on the left side of the tank. Most have an adjustment screw or sliding clip.
Lower the float slightly so the water level sits about ½ to 1 inch below the top of the overflow tube.
Flush and watch the refill cycle.
If the water no longer spills into the tube, you’ve solved the problem.
- Test the Flapper for a Slow Leak
If the water level in the tank drops slowly after filling, the fill valve will keep turning back on to replace lost water.
This often sounds like the toilet refills every few minutes.
How to test it:
Add a few drops of food coloring into the tank water.
Wait 15–20 minutes without flushing.
If color appears in the bowl, the flapper is leaking.
How to fix it:
Replace the flapper. They typically cost $5–$15 and install easily without tools.
Make sure the chain has slight slack but isn’t too loose.
A worn or warped flapper is one of the most common causes of constant refilling.
- Check for a Stuck or Faulty Fill Valve
If the fill valve continues running even after the tank is full and water is not leaking into the overflow tube, the fill valve itself may be worn out.
Signs of a failing fill valve:
• Hissing sound that doesn’t stop
• Float rises but water keeps running
• Water shuts off only if you tap or jiggle the valve
In this case, replacing the fill valve is usually the best solution.
Fill valves cost around $10–$25 and come with instructions. Most are universal and fit standard toilets.
Turn off the water supply before removing the old valve.
- Check the Float for Obstruction
If the float cannot rise freely, the valve won’t shut off.
Make sure:
• Nothing is blocking the float
• The float arm isn’t bent
• The float moves smoothly as the water rises
Sometimes simply adjusting or straightening the float arm restores normal operation.
- Inspect the Refill Tube Position
The small refill tube should clip to the top of the overflow tube.
If it’s pushed too far down into the overflow tube, it can create a siphon effect that slowly drains tank water, triggering continuous refilling.
The tube should sit above the top of the overflow pipe, not inside it.
Adjust if necessary.
Quick Toilet Refilling Checklist
Is water flowing into the overflow tube?
Lower the float.
Test flapper with food coloring.
Replace flapper if leaking.
Replace fill valve if it won’t shut off.
Make sure refill tube is positioned correctly.
When to Call a Plumber
Professional help may be needed if:
• Multiple fixtures are running or losing pressure
• You suspect a hidden leak in the supply line
• The shutoff valve doesn’t work
• Replacing parts does not stop the issue
In most cases, however, the fix is simple and inexpensive.
Final Thoughts
A toilet that won’t stop refilling is usually caused by a leaking flapper or a worn fill valve.
These are small parts, and they’re designed to be replaceable.
Start with the simplest checks first. Most homeowners can resolve this issue quickly with basic tools and minimal cost.
If you’re looking for a complete breakdown of common toilet problems and how they connect, see our full Homeowner’s Guide to Toilet Problems.