Why Does My Toilet Keep Running? Causes and How to Fix It

When your toilet keeps running, it can waste water, drive up your utility bill, and be quite noisy. Fortunately, this common issue can be fixed easily without needing a plumber. Typically, a running toilet doesn’t mean you need to buy a new one. Adjusting or replacing the toilet's overflow tube, flush valve, or fill valve usually solves the problem.

These parts are affordable and readily available at your local home improvement store, hardware store, and even some department stores. Here's how you can fix a toilet that won't stop running.

Why Does a Toilet Keep Running?

There are several reasons a toilet keeps running. Start by turning off the water supply to the toilet. Here are three main parts to check:

• Overflow tube: The overflow tube is a hollow tube connected to the flush valve. It stops the toilet tank from overflowing if the fill valve doesn’t turn off.
• Flush valve: The flush valve includes the overflow tube, tank-to-bowl hardware, a tank-to-bowl gasket, a flapper, and a chain. It opens the flapper to let water flow into the toilet bowl when flushed and closes the flapper to let the tank refill.
• Fill valve: The fill valve controls water flow into the tank from the main supply. It’s easier to replace than the flush valve, but you’ll still need some pliers.

What You’ll Need

Tools

• Channel lock pliers or pliers
• Screwdriver

Materials

Overflow Tube

• Replacement overflow tube (optional)

Flush Valve

• Cloth/towels
• White vinegar (optional)
• Replacement flush valve (optional)

Fill Valve

• Cloth/towels
• Bucket/sink
• Locking nut

How to Adjust or Replace an Overflow Tube

Check the Water Level

• Remove the tank lid and see if the water level is too high, causing it to flow into the overflow tube. If it is, lower the water level.
• If the water is not reaching the overflow tube, the problem is likely with the flush valve.

Adjust the Float Rod or Float Cup

Lower the water level by adjusting the float rod or float cup. A float rod is a horizontal rod that extends from the fill valve to the float ball, while a float cup is a small cylinder that slides up and down the fill valve with the water level.

Use a screwdriver, a set of channel locks, or pliers to turn the adjustment screw counterclockwise about a quarter turn to lower the water level. Continue adjusting until the water stops flowing into the overflow tube.

Verify the Overflow Tube Height

If the overflow tube is too short, water will keep flowing into the tank and out of the overflow tube. If that's the case, replace the flush valve (instructions below). Make sure the new flush valve is compatible with your toilet model.

Tip

Consider upgrading to a pressure-assisted toilet. These are less likely to clog and can offer better performance.

How to Replace a Toilet Flush Valve

Inspect the Chain

Make sure the chain is the correct length for the flapper to fully open and close. If the chain is too short, the flapper won’t close properly. If it’s too long, it might get stuck under the flapper, causing leaks.

Inspect the Flapper

• Turn off the toilet's water supply and drain the tank.
• Check the flapper at the bottom. If it’s dirty or slimy, soak it in white vinegar and rinse it with clean water. Replace it if it’s warped or worn.

Remove the Flush Valve

• Turn off the water to the toilet and flush to drain the tank.
• Use a cloth or towel to dry up any remaining water before disconnecting the water supply to the tank with channel locks.
• Disconnect the flapper and remove the tank-to-bowl bolts to take out the old flush valve.
• Lift the tank off the toilet to access the toilet-to-bowl gasket.
• Loosen the flush valve nut.

Install the New Valve

• Install the new flush valve.
• Tighten the flush valve nut.
• Replace the tank-to-bowl gasket.
• Carefully put the tank back in place.
• Reinstall the tank-to-bowl hardware.

Test the Toilet

• Reconnect the water supply and turn the water back on.
• Check for leaks at the tank's base to avoid accidental water damage.
• Flush the toilet to test the new flush valve and ensure the running stops once the tank refills.
• If the water keeps running, the tank-to-bowl gasket or the flapper might not be properly installed.

How to Replace a Toilet Fill Valve

Verify the Fill Valve is Faulty

Remove the toilet tank lid and check the water level and the height of the overflow tube.

If the overflow tube is the proper height and the water level is set about an inch below the top, but water still flows into it continuously, then the fill valve is the problem.

Turn off the Water and Drain the Tank

• Shut off the water supply to the toilet using the isolation valve on the inlet line.
• Flush the toilet to drain the tank.
• Soak up any remaining water with a cloth.
• Remove the water supply line by hand or use channel locks if it’s too tight.

Unscrew and Remove the Assembly

• Unscrew the locking nut on the bottom of the tank and pull out the fill valve assembly.
• Set the old fill valve in a sink or bucket to catch excess water.

Insert and Adjust the New Fill Valve

• Adjust the height of the new fill valve to match the specific tank and desired water level.
• Insert the threaded end of the valve at the bottom of the tank.
• Secure it to the tank with a locking nut to form a watertight seal.

Reconnect Water and Test

Reconnect the water supply and turn the water on. If installed correctly, the fill valve will immediately begin to refill the tank and stop when the float arm or float cup reaches the set level.

When to Call a Professional

If water is overflowing or nearing the rim of the toilet bowl while running, or if the problem persists after your repairs, turn off the water valve and call a plumber. There may be an additional clog or another issue with your toilet.

FAQ

What is the most common cause for a toilet that keeps running?

The most common causes of a running toilet are a faulty overflow tube, flush valve, or fill valve. Replacing any of these parts usually resolves the issue.

Will a running toilet eventually stop?

A running toilet seldom stops on its own. Jiggling the handle might temporarily fix the problem, but more often than not, you’ll need to replace some parts to solve it.

What are the signs of a toilet going bad?

If you're constantly fixing the toilet, it frequently clogs, flushes poorly, has cracks or puddles around the base, or is generally old, then it’s time to replace it.

What happens if your toilet runs all night?

A toilet running all night wastes water and can flood if it clogs. With a septic tank, it can quickly fill the tank, potentially causing a leak in the drain field.