Why Your Toilet Keeps Running (Common Causes & How to Fix It)

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A toilet that constantly runs isn’t just annoying, it can waste hundreds of gallons of water every day and increase your water bill. The good news is that most running toilet issues are caused by a few simple components inside the tank that are easy to inspect and repair.

Below are the most common reasons your toilet keeps running and how you can fix them.

1. A Worn or Dirty Flapper

The flapper is the rubber seal at the bottom of your toilet tank. When you flush, it lifts to allow water into the bowl, then closes to refill the tank.

If the flapper becomes worn, warped, or covered in mineral buildup, it may not seal properly. When this happens, water slowly leaks from the tank into the bowl, causing the fill valve to constantly refill the tank.

Signs this is the problem

• The toilet randomly refills every few minutes

• You hear a constant trickling sound

• The flapper looks brittle, warped, or worn

How to fix it

1. Turn off the water supply to the toilet.

2. Flush the toilet to empty the tank.

3. Remove the old flapper from the overflow tube.

4. Install a new flapper and reconnect the chain.

Replacing a flapper usually takes less than 10 minutes.

2. A Faulty Fill Valve

The fill valve controls how water refills the tank after a flush. If the valve becomes worn out or clogged with debris, it may continue running even when the tank is full.

Signs of a bad fill valve

• Water constantly flows into the overflow tube

• The toilet continues filling even after the tank is full

• The tank refills randomly without flushing

How to fix it

Replacing the fill valve is usually the best solution.

1. Turn off the water supply.

2. Drain the tank.

3. Remove the old fill valve from the bottom of the tank.

4. Install the new valve and reconnect the supply line.

Most modern fill valves are designed for quick DIY installation.

3. The Float Is Set Too High

The float controls the water level inside the tank. If the float is set too high, water will continuously spill into the overflow tube, causing the toilet to run nonstop.

How to fix it

1. Locate the float adjustment screw on the fill valve.

2. Turn it counterclockwise to lower the float level.

3. Flush the toilet and check the water level.

The proper water level should sit about 1 inch below the overflow tube.

4. The Chain Is Too Tight

The chain connecting the flush handle to the flapper can also cause a running toilet.

If the chain is too short or tight, the flapper may not fully close after flushing. Even a small gap can allow water to leak into the bowl.

Fix

Adjust the chain so it has a little slack when the flapper is closed.

5. Mineral Buildup or Debris

Over time, mineral deposits and debris can build up on toilet components like the fill valve and flapper. This buildup can prevent seals from closing properly.

Quick Fix

Turn off the water supply and clean the components with vinegar or a mild cleaner to remove mineral buildup.

Preventing Running Toilet Problems

Most toilet problems happen because the internal components wear out over time. Checking your toilet tank once a year can help prevent issues before they become bigger problems.

Common parts that eventually wear out include:

• Flappers

• Fill valves

• Float mechanisms

• Flush seals

Replacing these parts early can save water and prevent constant running.

Recommended Tool for Fixing a Running Toilet

If your toilet keeps running, replacing the worn components inside the tank is usually the fastest and most reliable solution.

One repair kit that makes this job simple is the Fluidmaster PerforMAX Toilet Repair Kit. It includes the most common replacement parts you’ll need for fixing a running toilet, including a new fill valve, flapper, and installation tools.

Instead of trying to replace individual pieces one at a time, a full repair kit lets you upgrade everything inside the tank in a single repair.

Many homeowners can install this type of kit in 30 minutes or less, making it an easy and affordable fix for a constantly running toilet.