Close-up view of a white porcelain toilet bowl with clean water continuously flushing, illustrating blog post, “How to Fix a Running Toilet.”

How to Fix a Running Toilet: Common Causes and Solutions

February 27, 2026

Hear a trickle of water in the bathroom and wonder, “Why does my toilet keep running?” A constantly running toilet is one of the most common plumbing issues homeowners face. Not only is the sound annoying, but it can also waste hundreds of gallons of water each day and increase your utility bill. The good news is, in most cases, the problem comes down to a few common issues inside the tank, such as a worn flapper, an improperly adjusted float, or a faulty fill valve.

How to Fix a Toilet That Keeps Running

Fixing a Worn or Misaligned Flapper

One of the most common answers to the question, “Why my toilet runs without stopping?” is a worn or misaligned flapper. The flapper is the rubber seal at the bottom of the tank that controls when water flows into the bowl.

Steps to fix it:

  1. Turn off the water supply valve behind the toilet.
  2. Remove the tank lid and inspect the flapper.

  3. If the flapper looks warped, cracked, or doesn’t seal properly, replace it with a new one.

  4. Make sure the chain connecting the flapper to the handle has a little slack so it can close completely.

This simple repair is often the quickest way how to fix a toilet that keeps running.

Adjusting the Float

Another common cause of a running toilet is a float that’s set too high. When the float sits too high, water continues to flow into the overflow tube.

Steps to adjust the float:

  1. Remove the tank lid and locate the float (usually attached to the fill valve).

  2. Adjust the float height by turning the adjustment screw or sliding the float down.

  3. Flush the toilet and watch where the water stops filling. The water level should sit about an inch below the overflow tube.

Lowering the float often solves the problem if you’re trying to figure out how to fix a running toilet.

Replacing a Faulty Fill Valve

If neither the flapper nor the float solves the problem, the fill valve may be worn out.

Steps to replace the fill valve:

  1. Turn off the water supply and flush the toilet to empty the tank.

  2. Disconnect the water supply line.

  3. Remove the old fill valve and install a new one following the manufacturer’s instructions.

  4. Turn the water back on and test the flush.

Need Professional Help?

Sometimes the issue goes deeper than a simple DIY fix. If you’ve tried these steps and your toilet still won’t cooperate, it’s time to call a professional plumber for toilet repair.

If you’re in Nashville, TN, Southern Plumbing Works is here to help! Our licensed, insured, and highly rated team provides fast, reliable toilet repairs and plumbing services. Contact Southern Plumbing Works today to schedule expert service and finally stop that running toilet for good.