How to Fix a Run-on Toilet: A Complete Guide

Tips and Tricks, – Are you tired of hearing your toilet constantly running? Not only is it annoying, but it can also lead to a higher water bill. A run-on toilet is a common plumbing problem that can easily be fixed with a few simple steps. In this article, we’ll guide you through the process of how to fix toilet running.

What is a Run-On Toilet?

A run-on toilet, also known as a phantom flush, is when water continuously runs from the toilet tank to the bowl, even when it’s not being used. This happens when the flapper valve in the tank doesn’t seal properly, allowing water to leak through and into the bowl.

Tools You’ll Need

Before you start fixing your run-on toilet, make sure you have the following tools:

  • Adjustable wrench
  • Flathead screwdriver
  • New flapper valve
  • New chain (if necessary)

Step-by-Step Guide to Fixing a Run-On Toilet

Step 1: Turn off the Water Supply

The first step is to turn off the water supply to the toilet. Look for the shut-off valve located behind the toilet tank and turn it clockwise to shut off the water.

Step 2: Remove the Tank Lid

Remove the tank lid and place it in a safe location. Be careful not to crack the lid, as it can be expensive to replace.

Step 3: Empty the Tank

Flush the toilet to empty the tank. This will make it easier to access the flapper valve.

Step 4: Remove the Flapper Valve

Locate the flapper valve in the bottom of the tank. It’s usually connected to the flush handle by a chain. Disconnect the chain from the flush handle and remove the flapper valve from the tank.

Step 5: Install the New Flapper Valve

Install the new flapper valve by attaching it to the hinge ears in the tank. Make sure the valve is centered over the drain hole and the chain is attached to the flush handle with a little slack. Trim the chain if it’s too long.

Step 6: Test the Flapper Valve

Turn the water supply back on and let the tank fill up. Flush the toilet and check to see if the flapper valve seals properly. If it doesn’t, adjust the chain until it does.

Step 7: Replace the Tank Lid

Once you’re satisfied that the flapper valve is working properly, replace the tank lid.

Troubleshooting Tips

If your toilet is still running after replacing the flapper valve, try the following troubleshooting tips:

  • Check the chain length: If the chain is too long, it can prevent the flapper valve from sealing properly. Adjust the chain so there’s a little slack, but not too much.
  • Clean the flapper valve seat: Over time, mineral deposits can build up on the flapper valve seat, preventing the valve from sealing properly. Use a scrub brush to clean the seat.
  • Replace the fill valve: If the fill valve is malfunctioning

If the fill valve is malfunctioning, it can cause a run-on toilet. The fill valve is responsible for refilling the tank after each flush. 

If it’s not working properly, it can cause the tank to overfill and the water to continue running. Consider replacing the fill valve if you suspect it’s the cause of the problem.

Preventing a Run-On Toilet

Preventing a run-on toilet is easy with these simple tips:
  • Regularly clean your toilet: A buildup of mineral deposits can cause the flapper valve to malfunction. Regular cleaning can prevent this from happening.
  • Replace old parts: If your toilet is older, it may be time to replace some of the parts, such as the flapper valve or fill valve. This can prevent future problems.
  • Don’t use the toilet as a trash can: Flushing non-degradable items down the toilet can cause clogs, which can lead to a run-on toilet.


Fixing toilet running is a simple task that can save you money on your water bill and prevent unnecessary noise. By following these steps, you can easily fix a run-on toilet and prevent future problems. 

Remember to regularly maintain your toilet and replace old parts to prevent a run-on toilet from occurring.

Frequently Asked Questions

  1. How do I know if my toilet is running?
  2. You can tell if your toilet is running if you hear a continuous sound of water running or if you see water running down the sides of the toilet bowl.

  3. Why does my toilet keep running after I flush it?
  4. A run-on toilet is usually caused by a faulty flapper valve that doesn’t seal properly. This allows water to continuously leak from the tank to the bowl.

  5. Can a run-on toilet cause damage?
  6. A run-on toilet can cause damage by wasting water and increasing your water bill. It can also cause noise pollution and be annoying to listen to.

  7. How long does it take to fix a run-on toilet?
  8. Fixing a run-on toilet usually takes less than an hour, depending on the severity of the problem and your experience with plumbing.

  9. Can I fix a run-on toilet myself?
  10. Yes, fixing a run-on toilet is a simple task that can be done by most homeowners. However, if you’re not comfortable with plumbing, consider hiring a professional plumber.

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