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Toilet Tank Leaks When Flushed: How to Fix

Published on August 29, 2023
Written by Bo
toilet tank leaks when flushed - full speed plumbing

Have you ever experienced that annoying moment when your toilet tank leaks every time you flush? Well, don’t fret because you’re not alone. Many of us have been in the same predicament. 

Let’s get into the reasons why your toilet tank leaks when flushed and how to deal with it once and for all! 

If you find you need a bit more help, our team at Full Speed Plumbing in Mount Vernon, WA, is always ready to lend a professional hand. 

What is a Toilet Tank Leak? — An Expert Overview

In layman’s terms, a toilet tank leak is a bit like a sneaky water thief that robs your wallet without you even realizing it. 

Essentially, water seeps from the tank down into the bowl or onto your bathroom floor. This can happen for many reasons, maybe a worn-out flapper or a faulty fill valve. But whatever the cause, it’s an issue that needs to be addressed promptly. Otherwise, you might find your water bill skyrocketing, and no one wants that!  

So now that we’ve got that clear, it’s time to delve into fixing this pesky problem.

3 Reasons Why Your Toilet Tank Leaks When Flushed

Toilet tanks may leak post-flushing due to a variety of reasons. Let’s break it down to three primary culprits:

  1. Worn-out Flapper: The flapper creates a seal within the tank. Over time, this rubber component can wear out or become warped, failing to form a solid seal. As a result, water continually leaks into the toilet bowl.
  2. Faulty Fill Valve: The fill valve controls the water level within the tank. If it’s malfunctioning, it could cause an overflow of water, leading to leaks.
  3. Broken Tank-to-Bowl Gasket: The gasket is the large seal that connects the tank to the toilet bowl. If this gasket has cracks or other damage, water will leak out whenever you flush it.

Remember, consistent leaks increase your water bill and can result in a significant amount of water damage in your bathroom, so acting promptly is crucial for your wallet and home’s health.

How to Fix a Toilet Tank That Leaks After Being Flushed in 6 Simple Steps

Fixing the toilet tank that leaks post-flush is comparatively easier than you think. Here’s a simple step-by-step guide to help you out:

Step 1: Shut Off the Water Supply

First things first, locate your toilet’s shut-off valve. It’s typically found on the wall behind the toilet. Turn it clockwise to cut off the water supply to the toilet.

Step 2: Empty the Tank

Flush your toilet to empty the tank. This step ensures that you can work on the toilet without any water getting in your way.

Step 3: Check the Flapper

The flapper is the rubber component that creates a seal within the tank. If it’s worn out or warped, it might be the culprit. If so, replace it with a new one you can find at any home improvement store.

Step 4: Examine the Fill Valve

The fill valve controls the water level in the tank. If it’s faulty, it could lead to an overflow and subsequent leaks. You might need to replace this with a new one, too.

Step 5: Inspect the Tank-to-Bowl Gasket

The tank-to-bowl gasket is the large seal that connects the tank to the toilet bowl. If there are any cracks or damages, replace it to prevent any leaks.

Step 6: Turn On the Water Supply

Once you’ve replaced the faulty components, turn the water supply back on. Monitor the toilet for any signs of leaks.

Congratulations! Now you know what to do if your toilet leaks when flushed from the tank. If you have any further questions about the process, don’t hesitate to reach out to one of our team members at Full Speed Plumbing.

What Are the Risks Related to Leaky Toilet Tanks?

If your toilet leaks from the tank when flushed, you should address the issue as soon as possible. Leaky toilet tanks can pose several risks, both immediately and over time. Here are some of the potential hazards:

  1. Increased Water Bill: Over time, water leaks can waste a surprising amount of water and lead to a noticeable spike in your water bill. This is essentially money going down the drain without you utilizing the services you’re paying for.
  2. Environmental Impact: Water wastage is a grave concern in an era of increasing environmental consciousness. Every drop of water that leaks from your toilet tank is a drop that’s not being put to good use. This cumulative wastage contributes significantly to water scarcity issues.
  3. Potential for Water Damage: If your toilet leaks between the tank and bowl when flushed, it can lead to serious water damage in your bathroom. This includes discolored tiles, mold, mildew, and even rot in wooden subfloors. These affect the aesthetic appeal of your restroom and can lead to costly repairs and health issues.
  4. Underlying Plumbing Issues: A leaky toilet tank may be a sign of more severe plumbing issues. It may indicate problems with your home’s plumbing system that could lead to more significant leaks or water damage if left unchecked.
  5. Unpleasant Odor: Persistent dampness due to a leaky toilet can create an unpleasant odor in your bathroom. This smell can permeate other areas of your home, contributing to an overall less enjoyable living environment.

Remember, it’s best to address these issues promptly to prevent more costly repairs down the line. 

Can You Call a Plumber to Fix Your Leaky Toilet Tank?


The DIY process isn’t everyone’s cup of tea, and that’s perfectly okay. If you’re apprehensive about tackling the leaky toilet tank issue, it’s highly advisable to call a professional plumber. They have the expertise and tools to complete the job efficiently and correctly, saving you time and potential frustration. 

After all, ensuring that your home’s plumbing is functioning to its full potential is critical to maintaining your home’s health and peace of mind. At Full Speed Plumbing, we’re always just a phone call away, ready to address your plumbing needs.

Toilet Tank Leaks When Flushed: How to Fix — Conclusion

In conclusion, a leaking toilet tank is not just an annoyance, but it can lead to significant water wastage, environmental impact, potential water damage, and even underlying plumbing issues. It’s crucial to act promptly to curb these issues. 

If DIY isn’t your style, don’t worry. Full Speed Plumbing is here to help. Our team of experts is always on call, ready to assist with your plumbing needs in Mount Vernon, WA. Don’t let a leaky toilet disrupt your peace of mind. 

Contact Full Speed Plumbing today, and let us ensure your home’s plumbing is functioning at ‘full speed’.

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