Do you want to learn why your toilet bubbles or gurgles when you flush it?
The most common reason is a drain clog, but a clog in the venting system (or even the rim jets) can also create air bubbles.
I invite you to also read my guide on sounds your toilet makes and what it means.
In this guide, I will go over…
- Why drain clogs cause bubbling
- Vent pipe blockages and toilet burps
- Tips on removing clogs
- Other possible reasons for toilet gurgling
Table of contents
Why Does My Toilet Burp Big Bubbles When Flushed?
The number #1 reason a toilet bubbles when flushed is because there is a partial clog in the drain line.
The partial clog in the drain line causes air to be pushed back towards the toilet when flushed — creating a large burp or gurgle when it’s flushed.
But there are other reasons for toilets burping when flushed such as a clogged vent pipe which creates something known as air lock. This lack of air venting can also cause a backward flow of air resulting in bubbles. Since the clog restricts the proper flow of waste water down the drain, the water in the drain/sewer pipes temporarily rises which forces air out of the toilet.
Another way it can happen is if the rim jets (along the rim of the bowl) get clogged with debris such as rust particles.
Keep reading for details on how to diagnose this problem and ways to fix it…
Read Also: How To Unclog A Slow Draining Toilet?
Drain Line Clog Creates Air Bubbles
Probably the most common reason that a toilet bubbles or gurgles when flushed is that there is a partial clog in the drain line. The clog can be from disinfecting wipes, paper towels, or other debris mixed with feces that doesn’t easily break down in the drain lines.
A partial clog in the drain line will allow air to be pushed backwards along the drain line because the water level will get temporarily raised in the drain pipes when you flush.
If the drain line was totally blocked, the toilet wouldn’t gurgle — it would just overflow and flood the bathroom.
A bubbling or gurgling toilet can actually be a useful warning sign that there is a problem with your drain or sewer line.
If your sewer line gets completely blocked, obstructed, or broken — it can cause thousands of dollars of damage to your front yard or result in home flooding.
If there are air bubbles when flushing the toilet, it can be the ‘canary in the coal mine’ that alerts you to potential disaster if not addressed.
Other Drain Problems
In addition to clogs, there can be a few other ways that the waste water gets restricted which can imitate an actual clog. A restricted drain line can happen from tree roots growing into the sewer line, a partial collapse of the drain line, or some type of damage.
And if you have old galvanized steel drain piping, the narrowing of the interior of the pipes may be restricting flow — mimicking a clog.
With old homes, even a poor layout or configuration of the drain pipes may be the culprit — restricting waste water flow.
Read Also: How To Flush A Toilet When The Water Is Off?
Probably the easiest way to remove a clog (if it works) is to use a simple plunger.
But before you start plunging the toilet, I recommend sealing the drains (and overflow drains) for the nearby bathtub, shower, and sinks. The nearby plumbing fixtures are likely connected to the local drain pipe that the toilet uses.
So if you use a plunger for the toilet while sealing off the other drains, it will create a better seal and you will have a greater chance of removing the clog.
To read more details on unclogging a toilet, check out my article on the top 4 methods to unclog a slow draining toilet.
The next step is to try to snake out the clog by using a toilet auger.
Snakes are simply metal cables with some type of bulb on the end that can clear out clogs.
Toilet augers are custom snakes that are made to be used with toilets, and you can use these snakes without removing the toilet. There is a plastic ‘sleeve’ that protects the porcelain toilet from scratches. You simply insert the steel cable into the toilet, and then rotate the handle.
There are also motorized snakes that you can rent from hardware stores. With these augers, you will need to remove the toilet — but they are more likely to remove heavy or far away clogs.
Using a motorized auger at a drain cleanout is also a good option which may allow you to get deeper into the sewer line and even out to the street.
If you have any doubts, hiring a qualified plumber to snake out your drain line is recommended.
Another option (before or after trying to snake) is to have a plumber do a camera scope of your entire drain system.
The nice thing about this strategy is that you will know exactly where the clog is, and the plumber may even be able to snake out the clog while physically viewing it on the monitor. And the camera system will show you the current condition of the sewer line all the way out to the street.
In addition, the toilet burps may be caused by tree roots, a collapsed sewer line, or degraded drain pipe system such as galvanized steel which rusts from the inside.
Read Also: What Are The Best American Standard Toilets?
Vent Pipe Clog Leading To Toilet Bubbling
After a problematic drain line, the second most common reason for a toilet that produces large air bubbles when flushed is a clogged vent pipe.
Every home usually has at least a few vent pipes that go to the roof. These vent pipes help the drain lines to flow smoothly by preventing air locks and trapped water in the sewer pipe. Most homeowners never really think of the plumbing vents, but they are a crucial part of the plumbing system.
Sometimes these vertical vent pipes can get clogged with debris such as tree leaves or birds nests.
When the air vent gets clogged, it will basically produce the same result as a drain line clog — causing water to rise as you flush the toilet which pushes air backwards and into the toilet.
Flashlight On Roof
The easiest way to actually see if there is a clog in a plumbing vent is to get on the roof.
You can simply tie a string or rope to a small flashlight and drop it down the plumbing vent. And even if you can’t see the clog, you may be able to ‘feel’ the clog if you drop a flashlight down the vent.
Clearing the Vent Clog
If you are certain that there is a clog in the plumbing vent, you have a few options to remove it.
Probably the most common method is to use a snake to try to clear the clog. You can use a simple manual snake at any hardware store, and for tougher clogs — you can rent a motorized snake.
In addition to snaking out the clog, you may also be able to clear the clog by dropping down a garden hose.
Slowly drop down the hose into the vent, and then have someone turn on the water supply from the ground. The hose should be set to a high water jet setting once it is turned on.
The risks of this method is that if there are any weak elbow connections in the piping system, it may cause leaking on the interior of home. I recommend having someone on the inside on the lookout for water leaks when you are doing this method.
Read Also: What Are The Best Dual Flush Toilets?
Rim Jets Clog Results In Toilet Burps
In addition to a drain clog and vent clog, there is one other way that large air bubbles may form when flushing a toilet.
Sometimes debris such as rust particles can clog the rim jets.
The rim jets are the small holes along the rim of the toilet that initiates a flush. These small jets create that ‘swirl’ which gets the flush started, and then the main jet (the submerged jet of water or ‘siphon jet’) flows into the bottom of the toilet bowl.
If the rim jets are clogged with debris, the toilet doesn’t fill up a little due to the rim jets. And when most of the flushing is done with the siphon jet, this type of flush can mimic a clog and create large or bubbles or burping when flushed.
Read Also: What Are The Best Bidet Toilet Seats?
Clean The Rim Jets To Prevent Toilet Burping
To solve this problem, first just flush the toilet and look close at the rim of the toilet bowl. Is water flowing out of the rim jets?
If it appears that the rim jets are clogged, simply get a coat hanger or a small wire, and insert it into the small holes to loosen any debris. After cleaning the rim jets of debris, flush the toilet again to see if it worked.