What to Do When Your Toilet Won't Stop Running

A running toilet is more than an annoyance—it wastes water and increases your utility bill. A toilet that continuously runs can waste up to 200 gallons of water per day. Fortunately, most running toilet problems have straightforward causes and solutions.

Understanding How a Toilet Works

To diagnose a running toilet, it helps to understand its basic operation. When you push the flush handle, a chain lifts the flapper, allowing water from the tank to flow into the bowl. As the water level drops in the tank, the fill valve opens to refill it. Once the tank reaches the proper level, the float shuts off the fill valve, and the flapper seals the tank.

Problems in any of these components can cause the toilet to run continuously. The key is identifying which part is malfunctioning.

Common Cause 1: The Flapper

The flapper is a rubber seal at the bottom of the tank that lifts during flushing and seals afterward to hold water in the tank. Flapper problems are the most common cause of running toilets.

Symptoms of Flapper Problems

You hear water running continuously or intermittently, and the tank water level may be slightly below the overflow tube. Jiggling the handle temporarily stops the running.

How to Check the Flapper

Remove the tank lid and look inside. The flapper should sit flat against the flush valve opening at the bottom of the tank. Press down on the flapper—if the running stops, the flapper is not sealing properly.

Check for visible damage: cracks, warping, mineral buildup, or deterioration from age or cleaning chemicals. The rubber should be smooth and flexible. Flappers typically last 3 to 5 years before needing replacement.

Flapper Fix

Turn off the water supply valve behind the toilet and flush to empty the tank. Unclip the old flapper and attach a replacement flapper of the same type. Turn the water back on and test. Flapper replacements cost under $10 and are available at hardware stores.

Common Cause 2: The Fill Valve

The fill valve controls water flow into the tank after flushing. If the valve does not shut off completely, water continues running.

Symptoms of Fill Valve Problems

Water runs constantly even when the flapper is sealing properly, or water sprays from the valve. The water level may be too high in the tank.

How to Check the Fill Valve

Lift the float arm or float cup. If the water stops, the fill valve is working, and you may have a float adjustment issue (covered below). If water continues running, the fill valve itself needs attention.

Check for debris in the valve. Sediment can prevent the valve from closing completely. Also check the valve diaphragm for wear or damage.

Fill Valve Fix

Turn off the water supply and flush to empty the tank. For minor sediment, remove the top cap of the fill valve and rinse it under running water. If cleaning does not resolve the issue, replace the entire fill valve—this costs $15 to $30 and requires basic tools.

Common Cause 3: The Float

The float controls the fill valve by rising with the water level. When it reaches the correct height, it signals the fill valve to shut off.

Symptoms of Float Problems

The tank overfills, and water runs into the overflow tube. You may hear water running constantly or periodically as the tank loses water and refills.

How to Check the Float

Older toilets use a ball float on a metal arm. Newer toilets use a float cup that moves up and down along the fill valve. The water level should be about an inch below the top of the overflow tube.

If the water level is too high, adjust the float down. If too low, adjust it up. For arm-style floats, bend the arm slightly. For float cups, locate the adjustment screw or clip and slide the float to the proper position.

Float Fix

Float adjustments are simple. For arm floats, gently bend the float arm downward. For cup floats, find the adjustment mechanism and move the float clip down. Test flush and adjust further if needed.

Common Cause 4: Chain Problems

The chain connects the flush handle to the flapper. Chain issues can prevent the flapper from sealing or lifting properly.

Symptoms of Chain Problems

The toilet runs when not in use, or the flush handle feels loose or stuck. The flapper may stay partially open, allowing water to leak continuously.

How to Check the Chain

Look for a chain that is too long and getting caught under the flapper, or too short and preventing the flapper from fully closing. Check for kinks, rust, or broken links.

Chain Fix

Adjust the chain length so there is slight slack when the flapper is closed, but no excess that can tangle. Most chains have multiple attachment points. If the chain is damaged, replace it with a universal toilet chain.

Common Cause 5: Overflow Tube Issues

The overflow tube prevents the tank from overfilling by directing excess water into the bowl. If the water level is set incorrectly, water flows into this tube continuously.

How to Check the Overflow Tube

The water level in the tank should be about one inch below the top of the overflow tube. If water is continuously flowing into the tube, adjust the float to lower the water level.

In rare cases, the overflow tube itself may crack, allowing water to leak. This requires tank replacement.

When to Replace Parts vs. When to Call a Plumber

Most toilet tank components are inexpensive and straightforward to replace:

• Flapper: Replace yourself; inexpensive and easy
• Fill valve: Replace yourself with basic tools; moderate difficulty
• Float: Adjust yourself; no parts needed
• Chain: Adjust or replace yourself; simple fix

Call a plumber if:

• You replace parts but the toilet still runs
• Water leaks from the base of the toilet (wax ring issue)
• The tank or bowl is cracked
• You are not comfortable performing repairs
• Multiple toilets in your home have the same issue
• You notice water damage around the toilet or floor

Water Waste from Running Toilets

A running toilet can waste significant water. Even a small leak wastes 30 gallons daily—a larger leak can waste hundreds of gallons. Over a month, this adds substantially to your water bill.

If you notice your water bill increasing without explanation, check all toilets in your home for silent leaks. Add food coloring to the tank water and wait 15 minutes without flushing. If color appears in the bowl, you have a leak even if you cannot hear it running.