Best Flushing Toilets

Toilet leaking from tank when flushed [How to fix?]

A toilet leak is one of the most common plumbing problems that homeowners experience at home. If your toilet is leaking every time you flush, there’s no need to panic. However, you should identify what’s causing your toilet tank to leak.

Some of the main reasons why your toilet leaks when flushed are due to a worn-out or faulty bowl gasket, loose tank bolts, or a cracked flush valve. Therefore, you should inspect all of these things before making any conclusion.

The good news is that you can fix all of these problems yourself if you have all the needed tools. And if you don’t have the tools or time to fix your leaking toilet tank, it’s best if you call a professional plumber. You can also get a tankless toilet, such as Toto G400 dual flush toilet or Kohler Veil smart toilet, to avoid this issue.

The easiest thing to fix is loose bolts. If the bolts on the tank are loosened, you can quickly fix them by tightening them. But if you have a worn-out bowl gasket or cracked flush valve, it would be best if you contact a professional plumber.

Regardless of what’s causing your toilet tank to leak, it would help if you fixed it immediately. If you don’t attend to a toilet leak, it can cause severe damage to your bathroom, which may become costly in the long term. That’s why you need to repair them right away.

In this guide, we’re going to direct you on how to repair your leaky toilet tank every time it’s flushed.

How to fix a toilet leaking from the tank when flushed

If you don’t have a one-piece toilet and your toilet has been leaking every time you flush it, you can fix it by inspecting it first. Depending on the cause of the leakage, here’s how you should fix the leaking toilet tank:

What could cause the toilet tank to leak water when flushed?

  • Bad toilet flapper
  • Faulty flush valve
  • Damaged Gasket
  • Worn-out Bolts or Nuts
  • Water supply line
  • Bowl and Tand are not connected properly, etc.

How to fix loose bolts that hold the tank to the bowl

Toilet leaking from tank when flushed

A separate tank and bowl normally accompany two-piece toilets. Bolts usually hold these two parts together. Most of the toilets feature three bolts that keep the tank in place on top of the bowl. So, if the bolts are not appropriately fixed or loose, the tank’s water may find its way into the bowl even after flushing. Faulty bolts also cause water leaks from under the toilet when flushed.

Related article: Check The Possible Causes and Solutions of Toilet Whistling

You will have to disassemble your toilet and use a wrench or screwdriver to tighten the bolts in such a case. Besides you should also screw the water supply line tightly. Nonetheless, it would be best if you avoided over-tightening the bolts, as this can cause more damage to your toilet.

If you notice that the water is still leaking when you flush, you should inspect the bowl gasket.

How to fix a worn-out or damaged bowl gasket

Toilet leaking from tank when flushed

 As stated earlier, a worn-out or damaged bowl gasket is one of the leading causes of water leaking from the toilet tank to the bowl after flushing. Also known as the spud washer, a damaged or worn-out bowl gasket can let water into the toilet.

To fix this issue, you will be required to replace the lousy bowl gasket with a new one. Note that a new spud washer comes with toilet tank bolts, rubber washers, and metallic washers. Here are the steps to follow:

Step 1: Drain the toilet tank

Toilet leaking from tank when flushed

Begin by switching off the water at the shut-off valve. The shut-off valve is usually located at the back of the toilet and on the left-hand side. Turn the valve clockwise.

Step 2: Empty the water into the toilet tank.

Empty the toilet tank by flushing the toilet. Hold the handle down until all the water is gone to get rid of a lot of water. Use a microfiber cloth or sponge to drain the remaining water in the tank.

Step 3: Remove the toilet tank from the bowl

Toilet leaking from tank when flushed

The next step is to disconnect the toilet tank from the bowl and check the flushing system. When you take a quick look into the empty tank, you will see the tank bolt’s head. They are usually tightened from below the toilet bowl with nuts. You can loosen and remove the nuts with the help of a wrench.

When you’re done loosening the nuts, you can lift off the tank and place it on a rag or cloth. You will see the toilet bowl gasket on the outer part of the flush valve covering the whole flush valve nut. Push and get rid of the two bolts from the inside of the tank. If the bolts are corroded, don’t reuse them.  

Step 4: Replace the bad bowl gasket with the new one

Install the new bowl gasket where the old one was positioned. Place the new bowl gasket where the old one was positioned. Make sure the new gasket covers the whole flush valve nut. Next, slide the metal wash into each bolt and follow it with the rubber washers. Avoid over-tightening the washers, as it can cause damage. Also, ensure the washers are made of rubber and not plastic.

Step 5: Install the toilet tank

Toilet leaking from tank when flushed

When you’re done replacing the old bowl gasket with the new one, return the toilet tank in its place. Start with placing a rubber washer, then a metallic washer, and finally, nuts into each bolt. Tighten them, but don’t over-tighten. Furthermore, ensure that the toilet flapper and fill valve sit appropriately in position and do not shift.

Step 6: Reconnect the water supply

Toilet leaking from tank when flushed

To complete the new bowl gasket installation, reconnect the water supply line at the back of the toilet. You can then turn on the shut-off valve. When the toilet tank is full, you can test and see if the water doesn’t leak from the tank after flushing the toilet. This repair should fix the problem. But if the problem persists, you should attempt this final method.

How to fix a toilet with a damaged or faulty flush valve

Toilet leaking from tank when flushed

Another thing that can make your toilet leak after every flush is a bad or damaged flush valve. If the flush valve is damaged or cracked, it will allow water to run from the toilet tank to the bowl. Also, it can make the toilet take longer to fill up. Besides, the toilet can have a weak flush.

Related article: Why Is Your Toilet Flushes Slowly When You Flush?

Nevertheless, all these can be fixed, and your toilet runs smoothly. The flapper is the first thing to check if you suspect the toilet is leaking because of a bad flush valve. If your toilet’s flapper is not sitting properly, is cracked, or is damaged, it will cause the toilet to leak from the top of the tank. The best choice is to replace it with a new flapper. Before you remove the flapper, inspect it and ensure it’s the cause of the leakage.   

Common toilet leak problems and solutions:

Toilet leakage problem Solutions
Toilet leaks between tank and bowl when flushed Replace the sponge gasket or use new washers.
The toilet leaks upon flushing between the tank and the Pedastal: Check the connection of the tank
When the toilet is flushed, water leaks from the discharge pipes: Tighten the flapper in the valve seat
American Standard Titan toilet tank leaks between the tank and the bowl: Change the seal and check the flapper
The Toilet tank holds water, but when flushed, water leaks out: Replace worn-out wax gasket and install new bolts
Swiss Madison toilet water leakage: Tighten necessary nuts and bolts
Airstream Macerator toilet leaking on the ground when flushed: Clear the waste and check the motor and microswitch
Niagara toilet tank gasket leakage problem: Change the gasket and bolts
When flushed, water comes out between the water closet and the commode: The seal between the bowl and tank might be damaged
Toilet bowel leaks from the base when flushed: Check the water supply line, tighten the nuts, and change the gasket


If you’ve had a two-piece toilet and it leaks from the tank every time you flush, you can inspect your toilet and fix the problem. The main reason why your toilet may have a leakage is because of a bad flush valve, worn-out bowl gasket, or loose bolts.

You can follow the procedures that we’ve discussed above to carefully and adequately fix your toilet. But if you don’t have the necessary tools and time to do it, you can always hire a professional plumber to assist you.


Hi, I am Jose S. Franz. Currently, I am working as a professional plumber, and our team offers various plumbing services at an affordable price. After my college education, I completed a vocational certification course in plumbing systems and worked with several construction companies. Since then, I have fixed lots of different toilet models, from older to the latest versions. So I have more than 22 years of experience installing plumbing systems and toilets in both residential and commercial buildings.

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