How To Fix a Running Toilet

A large amount of water on the floor is usually a sign of a fast external leak. Shut the water off now before you read any further. The first thing to do is figure out what’s causing the toilet to run.

• Is it running constantly or does it run for a few seconds at random times?
• Can you see water constantly flushing down the bowl or is it just running into the tank?
• Is there water on the floor around the toilet? A little bit or a lot?

A constant filling of the tank without water flushing quickly through the bowl is usually a problem with the fill valve. Water flushing through quickly is usually a case of a stuck flapper or flush valve.

Water running off and on at random times indicates a slow leak. This could be the flapper, flush valve or a small external leak. No water on the floor would indicate that the flapper or flush valve is the problem. Water on the floor would indicate a leak at the tank to bowl junction or at the connection of the fill valve.

A stuck flapper or flush valve can usually be fixed without turning off the water.

• Remove the lid of the tank.
• The flapper or flush valve is located in the center of the tank, at the bottom. It can get stuck in the open position, causing the water in the tank to constantly flush through the bowl.
• It’s common for the chain from the flush arm to get tangled. This will hold the flapper open. Untangle the chain and allow it to close. The chain may need to be adjusted to prevent this from happening.
• On older toilets with a float ball style fill valve, the flush arm and chain are close to it in the tank, and they may get tangled together. If this is the case, untangle and adjust.
• Sometimes, the chain will come loose and fall between the flapper and its seat. If this has happened, remove the chain and put it back into place.
• If none of these are the problem, check to see if the flush arm retaining nut has come loose. If it has, put the arm back into place and tighten the retaining nut.
• Many of these problems are caused by wear and tear, or the flush handle being pushed too hard or too far.
• Sometimes, a flapper will be damaged. (We’ll talk about that repair further down.)

Toilets with a button flush are usually one of two general types. The first is where the button activates the same system as a lever flush handle. The second is a dual flush toilet with a central flush valve. If your toilet is the first type, where pushing the button operates a flush arm inside the tank, the instructions are the same as a toilet with a lever handle. If the toilet is a dual flush, with two buttons in the center of the lid, follow the instructions that came with the toilet. If you no longer have the owner’s manual, it may be available on our site.

If the water is running constantly but the water isn’t running through the bowl quickly, the fill valve needs to be checked.

• Remove the lid of the tank.
• Lift up on the fill valve arm. If the water stops, the fill valve needs to be adjusted.
• To adjust the fill valve, turn the screw in the indicated direction until the water is about 1/4” below the top of the fill tube. You’ll need to “reboot” the toilet by flushing it between adjustments to see if it’s right.

If the water doesn’t stop when the arm is lifted, the fill valve needs to be repaired or replaced. We’ll talk about that repair further down the page.

Your toilet needs a repair but you’re not sure how to get started. Most repairs will require you to shut off the water and remove excess water from the tank.

Working with a toilet may seem unsanitary. But there’s good news. The water in the tank is clean. It’s coming from the same place as the water for your bath.

• The first step is to turn off the incoming water supply. This can usually be done with a shutoff in the floor or on the wall behind the toilet. If you don’t find one of these, you’ll need to shut off water to the whole house.
• Now, flush the toilet, but hold the handle down until water stops running from the tank into the bowl. If you have a dual flush toilet, hold the flush button down until water stops running.
• There will be some water left over in the tank. Remember, this is clean water that hasn’t been in the toilet bowl. You may see some sediment from the water or some mildew in the tank.
• This water needs to be removed, and it’s best to remove the sediment as well. You can absorb this water and wipe up the sediment with a towel or sponge, or vacuum it out with a wet vac.
• A wet vac is easiest because it can remove any sediment completely. Plain water can be disposed of down the drain, but if it has sediment in it, dispose of the water outdoors. A bucket can be used to squeeze water from the sponge or towel.
• Now that the tank is empty, you’re ready to replace a fill valve, flush valve, flapper, ready to rebuild the whole toilet, or remove it to install a new one.
• Even though all the visible water has been removed, there may be a small amount left in connectors, pipes or valves. Have a basin or a dry towel ready to catch drips.

This is the easiest, least expensive repair for a newer style fill valve.

• Remove the lid and set it aside.
• The fill valve is usually on the left side of the tank and is connected to the incoming water supply at the bottom of the tank.
• The seal is located in the top of the fill valve.
• Disconnect the float arm from the adjustment screw. It’s a snap connection, use care to avoid breaking it.
• Stabilize the upright stem of the fill valve by holding it with one hand. With the other hand, lift the arm, push down on the cap and rotate it 1/8 degrees to the left.
• Lift off the cap and find the rubber seal.
• Check the seal for cracks, damage and debris.
• If the seal is cracked or damaged, it can be replaced. You can find the replacement part at a local Home Depot store or online.
• If the area is dirty, clean it with a paper towel.
• While it’s open, take the opportunity to flush the valve with water. It may be easier to get a helper for this.
• Hold a cup or other container upside down over the top of the fill valve.
• Slowly open the supply shutoff, just enough for some water to come through the valve. Don’t open it too far or water will spray all over the bathroom.
• Allow the water to run for a few seconds, washing away any internal sediment.
• Replace the cap and seal by reversing the removal process.
• Reattach the float arm, then turn the water back on. Test flush a couple of times. Replace the lid.

If this doesn’t fix the problem, don’t worry, the whole flush valve is easy to replace and relatively inexpensive. We’ll tell you how to do that in the next step.

If replacing the seat disc and flushing the valve doesn’t fix the problem, the whole flush valve needs to be replaced.

If your toilet already has a newer style fill valve, a matching replacement can be installed. If your toilet has an older style ball and arm or other style, now is a good time to upgrade to a current fill valve.

The valve can be purchased separately or as part of a full toilet rebuild kit.

• Turn off the water. Flush the toilet and remove excess water as described above.
• Remove the fill tube from the clip.
• Loosen the supply line from the tank.
• Remove the nut that secures the fill valve, and lift the fill valve from the tank.
• Clean the tank around the opening.
• Use the old fill valve to set the height of the new fill valve. Place the new fill valve in the tank. Tighten the nut to secure the fill valve.
• Be sure to follow the manufacturer’s instructions. Use the gasket and only tighten by hand.
• Replace the supply line. Don’t over-tighten.
• Replace the fill tube. Turn on the water and check for leaks.
• Adjust the fill valve.

If you have an older 3 to 5 gallon flush toilet, consider upgrading the whole thing to a new water-saving model. You’ll save on your water bill and help conserve water.

If the water in your toilet tank fills with water or runs at seemingly random times, it has a slow leak. This is wasting water and needs to be fixed.

The most likely cause of this leak is a bad flapper or flush valve. A flapper is rubber and will degrade over time due to minerals and chlorine in the water. The seal around a flush valve is also rubber. If your toilet has a flush valve, refer to the instructions included with the new one for replacement.

If the flapper doesn’t fit tightly for some reason, the water leaks by slowly and the fill valve tops up the tank when needed. That’s why it runs for a few seconds at random times.

The seal area may need to be cleaned.

The flapper is easy to test.

• Remove the lid.
• Look at the center of the tank at the bottom.
• Is the flapper up or down? If it’s up, see if the chain is snagged on something, or if the flapper is hooked on something. Free the flapper and make the necessary adjustments and see if it falls back into place.

A similar problem may be caused by a loose flush arm.

On toilets with a lever-style handle, the nut that holds the arm and lever assembly to the tank can be loose. If this nut is loose, it can cause the pull chain to snag on itself or it can pull the flapper out of alignment. To fix this, untangle the chain, realign the flapper and then tighten the retaining nut.

If the flapper is up and appears to be floating instead of caught on something, it needs to be replaced.

If the flapper is down:

• Flush the toilet and look all around the opening that the flapper closes.
• Does it look like it needs cleaning? If so, clean with a paper towel.
• Watch the flapper fall back into place. Does it seem to fall into place squarely and seal the tank? Does the flapper itself look like it’s cracked or warped?

Replacing a flapper is easy.

• Turn off the water and flush the toilet. You don’t need to remove all the excess water.
• Make note of the chain’s length, then disconnect it from the flapper.
• A universal flapper will have several mounting methods. Select the one that corresponds to your toilet.
• Remove the old flapper, usually by unclipping it from the bracket, or slipping the rubber body up and off the stem.
• Reverse the process to install the new flapper.
• Connect the chain at the same length it was previously.
• Turn the water on and let the tank fill.
• Perform a test flush. The chain length or placement on the flush arm may need to be adjusted.
• Ensure that the flapper drops back into place on its seat and that it functions properly.

Another reason your toilet could be running constantly or randomly is an external leak. External toilet leaks waste water and can damage the area around the toilet.

Look around the toilet for signs of water leaking from it. Is the area wet? Are there any water stains?

• Check vertical surfaces near the toilet. Incoming water is under pressure and could be spraying from the supply line onto the wall.
• Is there water on the bowl, between the seat and the tank. You can check this with a paper towel if it's difficult to see.

If water is leaking between the base of the toilet and the floor, the problem is the wax ring. (Follow the instructions in our guide How to Install a Toilet.)

If water is leaking from the bottom of the fill valve, where the supply line attaches, look closer to see what kind of leak it is. Is the leak spraying out under pressure or is it dripping from the bottom of the tank?

If water is spraying out, there could be a crack in the end of the fill valve and it will need to be replaced. This was probably caused by over-tightening the nut. It could also be a faulty supply line or a faulty rubber washer in the connection between the two. Look for where the water is coming from to know which one to replace.

If water is dripping from the bottom of the tank, the leak is probably coming from where the flush valve comes through the hole in the tank. There are three likely problems. The least likely is a crack in the tank.

It’s more likely the nut is either too loose or too tight. If it’s loose, simply tighten it. Some nuts have ridges or wings for hand-tightening. Some have flat sides for using a wrench. In either case, just tighten until the leak stops, and don’t apply more pressure than is needed.

If it’s too tight, the rubber seal can be distorted, causing it to leak.

If tightening doesn’t fix it:

• Follow the procedure for shutting off the water.
• Disconnect the supply line then remove the fill valve.
• Inspect the area where the fill valve passes through the hole in the tank.
• Inspect the rubber seal at the bottom of the valve. Clean or replace parts, as needed.
• When reinstalling the fill valve, ensure that the gasket is in the correct place and isn’t disfigured in any way.
• Reconnect the water supply line and observe the connection for leaks.

Water can also leak from the connection of the tank to the bowl.

The tank attaches to the bowl by way of a gasket seal and two bolts. There is a bolt on the left and right side of the toilet, underneath the tank.

A good way to discover if water is leaking here is to use a paper towel.

• First, dry off the area behind the seat completely.
• Then, lay a dry paper towel between the seat and the tank.
• Watch to see if it gets wet from water leaking from the tank. This method can also help you determine which side is leaking.

If water is leaking from here, look to see if the tank is sitting level on the base.

• If the tank isn’t level, look at the connection on the high side and tighten the nut until the tank is level.
• If the tank is level, or if tightening one side doesn’t stop the leak, put the seat down and hold the bowl steady with pressure from a knee.
• Carefully try to move the tank. If it moves, both nuts may need to be tightened.
• Tighten both nuts an equal amount, keeping the tank level.

If tightening isn’t needed, or it doesn’t work, the gasket probably needs to be replaced.

• Follow the procedure for turning off the water.
• Inspect the area around the tank to bowl connection to see if the gasket is cracked or bulging to one side.
• Remove the two nuts that hold the tank and bowl together.
• Realign or replace the gasket.
• Reassemble the toilet and test for leaks.