If your toilet randomly runs throughout the day or you hear a ghost flush in the middle of the night, there could be a variety of culprits.

Before you hire a professional to replace your toilet there are a few steps you can take (besides jiggling the handle) to fix the problem on your own. It may be an issue with one of the following parts:

  • Flush chain
  • Toilet flapper
  • Float valve

Why My Toilet Randomly Runs?

close up view of toilet water flushing; toilet randolmy runs

There are plenty of reasons why you’re toilet could be non-stop running, but here are some of the most common:

  • Your chain could be too short, keeping your flapper from fully sealing to its seat
  • Your flapper may be damaged or dirty, preventing it from sealing properly
  • Your float valve could be set too high, so toilet filling is continuous

Below, we’ll go into detail on how you can test and fix each one of these issues. There’s a good chance that your toilet is randomly running because of these issues.

How to Fix a Toilet That Randomly Runs

If cleaning your toilet bowl is the extent of your bathroom plumbing skills, don’t worry. The steps in this troubleshooting guide don’t require any specialized tools or knowledge, and even if you can’t fix the problem on your own, the toilet tank will seem like a much less scary place.

Let’s get into more detail about the three major culprits of a toilet that randomly runs.

1. Check the Length of the Flush Chain

When you flush, the handle on the outside of the toilet tank controls a chain, which lifts a flapper that initiates the flush. When the flapper returns to its seat at the bottom of the toilet tank, your water supply will fill the tank with water, and the chain will return to its pre-flush position.

If the chain attaching your toilet handle to the flapper is too short, the flapper may not be sealing entirely once the flushing mechanism is complete, causing water to leak from the filling toilet tank into the bowl. If the tank water drips into the bowl, you’ll have a toilet that randomly runs or runs continuously.

Open your toilet tank lid, and perform a test flush. Watch as the handle pulls the chain, and make sure that there’s enough slack for the flapper to return to its resting position.

Consider Replacing the Chain

plumber fixing toilet chain; toilet randomly runs

If the chain is too short to allow the flapper to completely seal against its seat in the bottom of the toilet tank, you’ll need to either add more slack to the chain (most chains are adjustable) or purchase a longer chain.

Toilet chains are easy enough to remove and replace. Simply remove the chain from both the flapper and the handle inside the toilet tank, make sure that your new chain is long enough (but doesn’t have enough slack to disrupt the flushing process), and reattach it to both the handle and the flapper.

As always, try a test flush and shake the handle to make sure everything is working correctly.

2. Check the Toilet Flapper

If your chain is long enough to accommodate the flapper’s full range of motion, there may be an issue with the toilet flapper itself.

Toilet tank flappers are highly exposed to moving water, so they deteriorate with time. Since most of their time is spent submerged in a warm and wet environment, they’re also susceptible to hard water buildup, mold, and mildew growth.

Examine your flapper for signs of wear and tear or buildup. Remove it from the chain and detach it from the flush valve. Examine it thoroughly, keeping an eye out for:

  • Mold, mildew, or other buildups
  • Weak spots or vulnerabilities in the rubber
  • Chips in the rubber, especially around the outermost part, which seals to the bottom of the toilet tank

Clean or Replace the Toilet Flapper

A damaged rubber flapper valve is the reason this toilet randomly runs

If you notice any mold or mildew growth or mineral buildup on your flapper but no other abnormalities, wash the flapper thoroughly with hot soap and water. Consider adding water treatment to your toilet tank to prevent bacterial and mineral buildup that could speed up your flapper’s life cycle.

If your toilet flapper is chipped or damaged, replace it. Make sure to purchase the correct size: Taking your old flapper to the hardware store with you can help you choose the right one. Some flappers even come with a new chain, which you should install along with the new flapper.

3. Check the Toilet Tank Float Valve

The toilet tank float valve is an adjustable part that activates the water supply that fills your tank. When there’s enough water in the toilet tank for the float valve to float, the toilet stops running.

While your toilet is running, take a look at your float valve. Is the float set too high, preventing your water supply from turning off? It’s time for an adjustment.

Move the Float Down

hand fixing toilet float; toilet randomly runs

Move your float down so that it’s level with the fill line marked on the inside of your toilet tank. Make sure not to set the float too low, or else your toilet won’t flush powerfully.

Perform a few test flushes, and find a happy medium between high enough tank water level and strong enough flushes.

When DIY Fails, Paladin Plumbing Can Save the Day

Whether you’re a pretty handy person or a home repair novice, sometimes DIY fixes just don’t cut it.

If you’ve tried all of the tips above and still your toilet randomly runs, it’s time to call a plumber. At Paladin Plumbing, we’re here to help with anything from a running toilet to significant plumbing problems. Give our team a call and set up your appointment today!


Does phantom flushing raise the water bill?

Yes, phantom flushing wastes as much as 200 gallons of water per day and will increase your water bill. Phantom flushing is when your toilet continuously fills up due to a fill valve or flapper issue.

What happens if a toilet runs all night?

If a toilet runs all night it will waste water and increase your water bill. Excess water can potentially flood your septic tank and lead to failure and saturation of your drain field.

How long does a toilet flapper last?

The average toilet flapper lasts about 4-5 years. It’s important to replace your toilet flapper when needed to prevent water leaks.