Facebook
When you shop through links on our site, we may earn an affiliate commission. This educational content is not intended to be a substitute for professional advice.

Toilet Pipe Leaking When Flushed (and Why)

Updated
Ignore a leaking toilet at your peril. The problem will get worse if left unchecked.

If your toilet leaks when flushed, several things could be to blame. However, the solution could be as simple as tightening a few bolts to a more in-depth toilet replacement.

So, if your toilet is leaking when flushed only and not at any other time, it’s time to don your detective’s hat and investigate.

Toilet Leaks Every Time You Flush

There are several reasons why your toilet only leaks every time you flush. It could be simple as loose mounting bolts or a perished wax ring at the toilet’s base. You might have a cracked toilet flange or a loose fill valve inside the toilet’s tank. The issue might even be a broken seal between the tank and toilet bowl, causing water to drip out of the back.


Why Is My Toilet Leaking When Flushed?

There are several reasons why your toilet leaks when flushed. It’s fair to say that human nature tells us that a dripping toilet is a minor problem and can be sorted out later. Unfortunately, the one thing guaranteed with a leak is it gets worse when unchecked.

That drip becomes a trickle and then a river. It puts strain on your toilet’s working parts and wastes a lot of water. So, the watchword is urgency when it comes to leaks.

Luckily, most are simple to address. Let’s take a look at the usual suspects.

Wax Ring Problem

The wax ring sits at the toilet’s base, sealing the toilet and the sewer pipe gap. It prevents odors and water from leaking.

The Problem

If you’ve recently replaced the toilet and not the wax ring, it could cause the old ring to leak water. The wax dries, cracks, and eventually splits over time.

How to Fix It

There is no other solution for a faulty wax ring other than replacement. You will need to drain the water from the tank and bowl, remove the toilet and swap the wax ring. To empty the toilet cistern, isolate the water at the supply valve on the wall, and flush.

The water empties out of the toilet so that you can unbolt the base to remove it. Luckily, you can buy a new wax ring cheaply. They are available on sites like Amazon or from your local hardware store.

Toilet Flange Issue

Your toilet flange sits under the toilet base to anchor the toilet to the floor. It connects the toilet to the sewer pipe and helps to hold the wax ring in position.

The Problem

Toilet flanges are hard-wearing, so they rarely malfunction. However, that doesn’t mean they never go wrong. The most common problems include cracks or splits in the flange.

How to Fix It

The harsh reality is that you will need a brand new toilet flange if you want to solve your leak. The best approach is to examine the flange when replacing the wax ring. It makes sense because the toilet is already removed, saving you from draining the system again.

There isn’t much point in removing the toilet and swapping the wax ring when the flange has a crack in it. You can pick up toilet flanges for a reasonable price on sites like Amazon. This Fluidmaster is a great example of an affordable and popular toilet flange.

Flapper Problems

The flapper connects to the lift arm on the flush lever. When you engage the flush valve, the flapper lifts, and when the water drains, the flapper lowers back over the water inlet. This stops water from flowing into the bowl, and the cistern refills with water.

The Problem

There are several causes of a faulty flapper. The chain linking the flapper to the lift arm could be too short, causing the flapper to remain open. Water then flows into your toilet bowl continuously, causing that gushing sound.

Excess water continuously running is bad news for your toilet system and the planet. It wastes a precious resource and puts undue strain on the toilet. It also hammers your wallet with increased water bills.

The flapper could also perish, especially in hard water areas. Mineral deposits coat the flapper, making it brittle. Over time, bits snap off, and the flapper fails to seal the water inlet.

How to Fix It

If the chain is too short, you can purchase a replacement, like this pack of three chains, or add more links to the existing chain. Flapper chains are so inexpensive that you may as well replace the entire thing.

If the flapper has perished, the only solution is a new one. Again, like most toilet-tank components, new toilet flappers are cheap. This Toto model even comes with a replacement chain.

Loose Tank Bolts

Your toilet tank attaches to the base via a series of bolts. They connect the tank to the bowl with a rubber gasket to seal the inlet.

The Problem

Dripping at the back of the tank could result from loose tank bolts. This may be an installation error, or they have worked loose over time.

How to Fix It

You will need an adjustable wrench and pliers for this fix. Grip the base of the bolt with the pliers and the top nut with the wrench. Tighten the nut until you can’t turn it anymore.

Take Note

Don’t overtighten the nut, or you risk cracking the porcelain. If you hear metal scraping ceramics, stop!

Cracked Toilet Bowl

Old toilet bowl lying discarded on the nature in forest

Porcelain toilets are robust and last for years, but sometimes they weaken and crack. The damage may not be noticeable until water starts pooling from the base of your toilet.

The Problem

Hairline cracks and minor chips weaken the toilet’s structure and drip small amounts of water. These cracks sometimes occur when the toilet has experienced an impact of some kind. It could be as simple as dropping an object on the toilet or bowl.

How to Fix It

If you notice water stains through the ceiling below an upstairs bathroom, it could signify a cracked toilet bowl. You can take the temporary approach and repair the crack with epoxy resin or replace the entire toilet bowl. This Loctite resin glue is ideal to use on cracked porcelain.

Water Leaking Under Toilet Bowl When Showering

If you have water leaking under the toilet every time you shower, it is likely a drain line issue. When the water from the shower drains away, it backs up and looks for the nearest exit point, which could be your toilet.

To solve the issue, you will need to inspect your plumbing for leaks, cracks, loose connections, and dreaded blockages.

You can use a chemical unblocker like this Drano Max Gel solution. Simply pour it down the drain, wait the allotted time for the chemicals to work, and then flush with water. The downside to using this formula is it is bad for the environment.

But on the plus side, it is easy and convenient, and it gets the job done.

The other alternative is to use a toilet auger attached to a long coil. These handy tools are called drain snakes. This pack of seven snakes also includes hair removers, which is one of the most common reasons why your drains get clogged.

When to Hire a Professional

Sometimes you have to admit defeat and call in the pros. If you’ve covered all the points above and still can’t locate the leak source, a plumber will sort it quickly. They have the experience, tools, and knowledge.

If you have water pouring through the floor or water running into a basement, it is likely a problem beyond your skill set. Whenever you have large volumes of water flooding your home, pick up the phone and call in the pros.

When to Replace a Toilet

Your average toilet will last for 20 to 30 years, but that doesn’t mean it will stay in fashion. Occasionally, things malfunction and need replacing, but for the most part, the toilet is rarely the issue.

You are most likely to experience component failures related to the tank mechanisms. They are often plastic and perish over time with mineral build-up.

If you have a cracked or chipped toilet bowl, it is time to bite the bullet and get a new one. Sure, it will cost you, but it will last the distance. A cracked toilet bowl is a ticking time bomb and will undoubtedly worsen.

Why wait until you are knee-deep in toilet water when you can nip the problem in the bud.


Flushed With Success

So, let’s take it from the top: if you’ve Googled, “why is my toilet pipe leaking when I flush?” and you are reading this for solutions, congratulations. You’ve found the most comprehensive article on the subject.

Hopefully, your takeaway from this is that most leaks are relatively easy to rectify and that plumbing and bathroom fittings aren’t as complicated as you might think.

Don’t suffer that leak in silence; get the tools out and fix it yourself. You can do it because you are a plumbing superhero.

Feedback: Was This Article Helpful?
Thank You For Your Feedback!
Thank You For Your Feedback!
What Did You Like?
What Went Wrong?
Headshot of Mark Weir

About the Author

Mark Weir

Mark spent 24 years working in real estate, so he knows his way around a home. He also worked with contractors and experts, advising them on issues of planning, investments, and renovations. Mark is no stranger to hands-on experience, having renovated his own home and many properties for resale. He likes nothing better than seeing a project through to completion.