Home Improvement

How to Fix a Leaking Toilet Tank

A constantly leaking toilet tank can easily drive anyone insane. There are so many possible reasons for the tank to be running, and luckily, most of them are easily fixable without having to involve a professional plumber.

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In this helpful guide, the Fantastic Services team will explain how to fix a leaking toilet tank by yourself, as a true professional would. This article is for anyone who wishes to stop that leaking toilet sound once and for all.

Reasons for a leaking toilet tank

The system of the tank is a simple one, however, there are a few parts that could cause the water to run due to damage. Here are the most common reasons:

Defective flapper

A flapper is the rubber part of the system within the toilet tank that lifts up to release water into the toilet bowl once you flush. After that, it goes back down to seal the opening and let the tank fill with water again. The most common reason for a leaking toilet problem is when the flapper cannot properly seal the opening. Often, this is because of the chain that holds the flapper gets caught on something and makes it impossible for the rubber seal to do its job. To fix this, a simple readjustment by hand will be enough. The other option that the flapper might be damaged due to deterioration over time. If this is the case, you will need to replace the flapper with a new one.

Damaged overflow pipe

The overflow pipe is a small plastic tube standing upright in the middle of the toilet tank. Its purpose is to drain the excess water when the tank fills up so it doesn’t end up spilling water. If you see that the fill tube is underwater, or if it’s broken, this might be the cause of your leaking toilet. You might have to replace the overflow pipe with a new one if you notice damages. If not, you just have to readjust the water level inside the tank.

The water level needs adjustment

The toilet float is another part of the system that regulates the water level inside the toilet tank. It comes in two variations – as a cup float and as a rubber ball float. If your toilet bowl is a new model, you probably have a cup float. If the water level is so high that it rises above the level of the overflow pipe, you’ll have to readjust it through the float.

If your toilet leaks only after use, then check our post on toilet leaks when flushed.

How to fix a leaking toilet tank

As you see, the mechanism inside your toilet isn’t a very complicated one, and with a little patience and understanding, you’ll be able to fix any small problem yourself. Of course, first, you’ll have to be certain you know the nature of the issue.

  1. Remove the toilet tank lid and look inside. Prepare a few towels, because you will possibly get wet. We also recommend using rubber gloves. Hold either end of the toilet tank lid with both hands and pull it out of the way. Toilet tank lids are heavy, so put it on the floor where it won’t break. If this is your first time looking at the mechanism of the toilet tank, give yourself some time to be sure which part is which.
  2. Check the overflow pipe. You will immediately notice whether the water level is above the overflow pipe. If this is the case, you know where the problem is.
  3. Check the flapper chain. If you see the chain that holds the flapper being caught on something, this should be your next sign. The problem might be exactly that. 
  4. Flush the toilet to see what happens. If everything seems in working order at first glance, do a quick experiment to see how the machine does its job. Sometimes the problem becomes clear once you put it to the test. If you flush the toilet and you see the flapper is still unable to seal the opening, then this is your issue. 
  5. Press on the flapper. A single finger is enough. If the water stops running in the toilet bowl, you can rest assured, this is your problem. The reason the flapper is not sealing properly might be because it’s damaged beyond repair due to wear and tear. You might have to replace it altogether. 

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How to replace a defective flapper

Once you’ve diagnosed your problem, it’s time to fix it. Replacing a toilet flapper is easy, you just need to follow these steps.

  1. Drain the tank and switch off the water. No matter the type of repair you decide to do, always drain the tank and switch off the water supply first. 
  2. Clean up the old dirty flapper. Before you run to the store for a replacement part, remove the old flapper by unhooking the sides from the pins at the bottom of the overflow tube. Look at it from up close and clean it up from mineral deposits. 
  3. Test the old flapper one last time. After cleaning it, put it back to its place and flush again. If the problem persists, you would have to buy a new one. Take the flapper with you at the home improvement shop to make sure you get the same one.
  4. Replace. To attach the new flapper, fit in into place and attach the hooks on the side to the pins on the overflow pipe. 
  5. Test. Turn the water back on and let the tank be filled completely. Watch the toilet bowl to make sure the water is not running anymore. Flush the toilet once and observe how the mechanism works with the new part. 

How to adjust the water level

If the problem isn’t the flapper, but the water level being above the overflow pipe, you will have to adjust it. The water enters the toilet tank through a fill valve. The float on the valve adjusts the water level and tells it to shut off when the tank is full. Therefore, you can lower the water level in the tank by adjusting the float.

If you have a ball float

A ball float has a long arm attached to the fill valve. At the end of it is a rubber ball-shaped float. To adjust the water level, you have to turn the screw attached to the fill valve. Use a screwdriver and turn counterclockwise to lower the float.

If you have a cup float

A cup float has a small circular cylinder wrapped around the fill valve. The cylinder can slide up and down and its position determines the water level. Just lower the cylinder and the water level will be adjusted.

Fill the tank with water and flush. Observe whether the water level gets over the overflow pipe. If it does, you would have to adjust the level again. Ideally, the water level should be about 3 centimetres below the top of the overflow tube.
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How to replace an overflow pipe

Finally, if the problem is not the water level, but the damaged overflow pipe, you would have to replace it. 

  1. Drain the tank and shut off the water to the toilet. Flush the toilet and shut off the water supply valve to keep the water out of your work area. Remove the remaining water inside the tank with a sponge, until it’s empty. 
  2. Take off the bolt. On the bottom of the toilet tank is a bolt designed for the flush valve. Use a wrench to loosen it up and take it off with your fingers. Once the bolt is removed you can take out the old overflow pipe. Just like with the flapper, you could take it with you to the home improvement shop in order to make sure you purchase the right replacement.
  3. Replace with the new overflow tube. Remove the plastic outlet ring and the washer and replace them while you are replacing the old overflow pipe with the new one. Line up the new overflow pipe the same way as the old one and secure it carefully in its place with the bolt.
  4. Adjust the float again. Once the new overflow pipe is there, look around to make sure the mechanism inside the toilet tank is the same as before. This includes adjusting the float at the same water level since it might have shifted as you were installing the new part.
  5. Flush and test. Turn the water back on and let the toilet tank fill with water. Check the water level, and make sure the new overflow pipe is above the water. Adjust the float again if you have to. No excess water should be running in the toilet bowl anymore. Flush the toilet. If there is no problem, you can put the lid of the toilet tank back on.

If you need to know more on this topic, check our post on how to fix a leaking overflow pipe.

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  • The toilet mechanism is simple and doesn’t warrant the help of a professional technician unless a full toilet bowl replacement is required.
  • The most common reason for a leaking toilet is a defective flapper.
  • If the problem is not the flapper, usually the water level needs adjustment.

Now you know how to fix a leaking toilet tank all by yourself. Rest assured, the sound of running water in the toilet will be a thing of the past. Of course, if you don’t want to get your hands wet, or have no time to do this, you could always rely on the professional handyman from the Fantastic Services team.

Image source: New Africa/shutterstock.com


Have you ever repaired a toilet tank on your own? Share your experience with us in the comments!

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