How to Fix a Toilet that Bubbles/Gurgles When Flushed

Last Updated on January 3, 2022 by toilethaven

Why Does a Toilet Bubble When Flushed?

A toilet bowl is designed to retain some water at the bottom, in what is called the P-trap This water acts as a barrier preventing sewer gases/smell from coming up to your bathroom.

When your toilet bubbles/gurgles every time you flush it, it is a sign that either the drainpipe or vent stack are clogged, or the septic tank is full. This creates negative air pressure inside the pipes which is forced out through the toilet bowl water in form of air bubbles, sometimes with a gurgling sound.

A bubbling/gurgling toilet should be fixed as soon as possible as it is a sign of a bigger problem waiting to happen. If your toilet bubbles when flushed it means your waste is not flowing out, but is rather building up in the drainpipe.

Every time you flush the toilet, it displaces air out of the pipe which escape through the bottom of the toilet in form of air bubbles.

If a toilet that is bubbling when flushed is not fixed in good time, it will lead into a backup. A backup happens where instead of the toilet channeling the waste into the city’s sewer lines it flows back to your toilet, bathtub drain, sink drain or any other drain in the house.

How a Toilet Works

toilet bowl

Toilets are dependent on gravity in order to flush and that is why the water tank is placed above the bowl. When you flush the toilet, a large volume of water is released into the bowl forcefully in a short period of time.

This sudden dumping of water into the bowl causes a pressure differential between the bowl and the drainpipe. This pressure imbalance initiates the siphoning of the waste into the toilet drainpipe. The waste therefore flows through the drain and into the city’s sewer lines. Read more on how a toilet works here.

A little amount of water flows into the toilet bowl from the tank. This is the water you see at the bottom of the toilet bowl which prevents sewer gases from coming up into the bathroom and entire house.

The sewer gases instead move up the vent stack and escape through the roof of the house. If the vent stuck is blocked, the air will have no way of moving out and therefore will force their way through the toilet bowl which results into a bubbling toilet after flushing.

How to Isolate a Toilet That Bubbles After Flushing

A house has a network of drainpipes from the toilets, sinks, laundry rooms and bathtubs which all link up into the main house drainpipe before flowing out to the sewer line and finally into into the city sewer line.

Before you start fixing a toilet that bubbles/gurgles when flushed, you need to be sure whether it is only the toilet that is clogged or the entire house drainage is clogged.

The following are some of the signs to look out for:

1. Bathtub Drain Gurgles When Toilet is Flushed

If the house’s main drainpipe is clogged and then you flush the toilet, the toilet waste will have to displace the air in the drainpipe since it can’t flow out.  The air displaced, just like electricity will follow the path with the least resistance, which in this case is the bathtub drain and hence the gurgling as the air escapes.

It is easier for the air to escape through the bathtub drain than the toilet bowl since the water at the bottom of the bowl will act as a barrier.

2.Toilet Bubbles when Bathtub drains

A bathtub drain and a toilet drain are connected to the main house drainpipe. If while draining a bathtub you notice your toilet bubbling/gurgling, it is a sign that the house’s main drain is clogged.

Open the bathtub water faucet and let it drain as you watch inside the toilet bowl. If you notice any bubbles then it means the problem extends beyond your toilet drain.

If however the tub drains as usual without any bubbling in the bowl, the problem is therefore with your toilet drain. This is a much easier problem to resolve.

3. Toilet on a Septic Bubbles When Flushed

If you use a septic tank and you notice that your toilet bubbles when you flush it, it means either the septic tank is full or the drainpipe to the septic is clogged.

If the tank is full you undoubtedly need to empty it but a clogged drainpipe can be easily unclogged either by yourself or a plumber.

4. Talk to Your Neighbors

Plumbers are not cheap. Before you therefore enlists the services of one take your time to talk to your neighbors to see if they have the same problem as you do.

It is very possible that it is the city’s sewer lines that are blocked which in this case should take the responsibility of unclogging them.  You see, being cool with your neighbors has its advantages.

How to Fix a Toilet That Bubbles/Gurgles When Flushed

If after investigating you found out that it is not only your toilet drain that is clogged but rather the entire house, the best idea is to call in a professional plumber. Some people however will advise you to remove the main sewer cleanout plug and snake the toilet from there.

Why is it a bad idea to try and do this on your own? The whole house’s waste has been piling up inside the main drainpipes for some time. This means that the waste inside the drainage is under pressure.

If you go ahead and remove the plug, you will have the sewage spilling all over your propert. It is therefore bad advice to do it and will cost you so much more in the end.

If however the bubbling toilet problem does not involve other house’s drains, you can go ahead and troubleshoot it. There are 4 methods to do it:

1. Unclog the Toilet Using a Toilet Plunger

A toilet plunger is rubber cup with a stick that is used to unclog toilets. It works by creating a pressure differential between the clog and the bottom of the clog where the pressure below the clog is less than the exerted pressure resulting in the clog being sucked inside the drainpipe.

A plunger also works by sucking the clog into the bowl. Invest in a good plunger which will fit properly on the opening at the bottom of the toilet to create a good seal.

To plunge properly, make sure your first plunge is gentle as you engage the plunger properly on the toilet opening. Once it is properly engaged, go ahead and plunge hard. Hopefully, the clog will be dislodged and the toilet will stop bubbling.

To check if the problem is solved, flush the toilet again and see if it bubbles/gurgles. If successful then well and good. If not move to the next method. More on how to use a toilet plunger here

2. Unclog the Toilet Using a Toilet Auger

A toilet auger or a plumber’s snake is a long cable with a head and a cranking handle that is used to unclog toilets by shredding the clog into smaller pieces or pulling them out. Unlike a plunger, the snake goes inside the toilet trap and into the drainpipe where it acts directly on the clog if it’s within its reach.

Most toilet augers are between 3 to 6 feet but professional plumbers often use motorized augers which can exceed 100 feet. Again, if you can’t unclog a toilet with the standard auger you should call in a plumber because if the clog is way too deep in the drainpipe he/she might have to remove the toilet.

A standard toilet auger however works most of the time. Flush the toilet and look if the toilet is still bubbling or the problem is resolved. To learn how to use a toilet auger without scratching your toilet bowl check out this post.

If this also does not work out, you still have one more thing to try.

3. Check and Unclog the Vent Stack

You never know how important a vent is until it get clogged and sewer gases are backing up in your kitchen sink drain, bathtub drain or a toilet that bubbles when flushed. Your entire house will be smelling like a sewer.

When your toilet vent stack is clogged, sewer gases get trapped inside the vent stuck resulting in building up of negative air pressure. When the pressure is more than the toilet bowl water barrier can contain, it starts escaping through the water in form of bubbles and hence the gurgling.

To unclog a blocked vent stack, climb up to the top of the roof of your house with a garden hose using a ladder. Check if you can see the clog from the top, or if you can reach it with your hand. Sometimes it is a bird’s nest, dry leaves or trapped dead rodents/birds.

If you cannot see or remove anything with your hand, use the garden hose to pour water down the vent stack. The water with the help of gravity will wash the clog down the drainpipe.

While climbing to the roof, have someone hold the ladder down for you to avoid slipping.

4. Call a Plumber

Experience is everything, and that is why your plumber will charge you upwards of $150 to fix the problem for you. The plumber has experienced such problems before and has many tools that you might not have at your disposal and it makes sense to bring one onboard if you can’t seem to resolve the problem on your own


A toilet that bubbles when flushed can be an easy thing to fix or a complicated one. It can also deteriorate into a nightmare if left unfixed. The best thing is therefore to fix a bubbling toilet as soon as you detect the problem or you when you detect your other house drains gurgling when the toilet is flushed.


  1. Why does my bathtub fill when I flush the toilet?

The toilet drain and the bathtub drain are connected to the main house drain. If the main house drain is clogged, the waste is trapped in the drainpipes hence building up pressure. When you flush your toilet, the trapped water air and water backs up through the bathtub or other drains in the house. Sometimes you can also hear the bathtub drain gurgling when you flush the toilet.

2. Can you flush broken glass down the toilet?

No.  Broken glasses cannot be siphoned by the toilet, and even if they are siphoned they would clog the toilet at the trap or further down in the drainpipe. That will end up being a very expensive repair.

3. Can you flush drinks down the toilet?

Yes. Drinks are liquids and can therefore flow down the toilet drain easily without clogging it. The drink should however be flushed without broken glasses or crashed cans. These will surely clog the toilet.

4. Why is my toilet tank bubbling after flushing?

Bubbles in the toilet tank are a sign of presence of air in the toilet water lines. This is also characterized by a sputtering sound as the toilet refills. To remove the air in the lines, flush the toilet repeatedly until all the air comes out.

5. Why is my toilet bubbling and won’t flush?

The toilet is clogged either close to the toilet drain opening or a little further down in the drain which works against the siphoning action of the toilet. Try using a plunger to unclog the toilet and if unsuccessful upgrade to a toilet auger/snake.