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Why Does Your Toilet Bubble When The Bathtub Drains? An Easy Fix

Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases.

A functioning bathtub shouldn’t have any impact on the toilet. Whenever you notice a toilet bubbling at any given time, you should drain the bathtub accordingly and fix it as soon as you can.

This is because if the toilet bubbles whenever you drain the tub, it can be an indication that the vent stack or drainpipe has become blocked.

This can cause negative air pressure to build up inside the drain pipe or vent which concludes in air being forced out through the toilet.

Despite the fact that both a bathtub and a toilet are independent of each other, their drainpipes will be joined together within the main drain pipe that runs throughout the house.

Due to this close proximity, they tend to share the same vent stack. Any issue with one of their drainage systems will inherently impact the other fixture.

You should imagine the plumbing within a house as being like a tree as it tends to have a trunk and numerous branches.

Each individual branch will represent a singular fixture within the house which drains back into the main drainpipe aka the trunk.

Clogged Drainpipe

If the main drainpipe running throughout the house becomes clogged, you will inherently have an issue with the other fixtures within the house.

Therefore you might not notice that your toilet bubbles up when flushed. The following issues may also occur:

As a vacuum is not able to exist, the space between the clog and the tub will remain full of air.

So, whenever you drain the tub, the water displaces any air in the drainpipe. This air then forces through the bottom of the bowl and this is the key reason why toilets will bubble whenever a tub is drained.

It also may not be the main house drain pipe that has become clogged. These issues are also often caused by the pipe that connects the toilet and the bathtub.

Thus, in order to ascertain which pipe contains the blockage, you should turn on the water in your sink and listen for any bubbling in the toilet.

If it begins to bubble, then you can safely say that it is the main drainpipe that has become clogged. Conversely, if it fails to bubble, then the issue resides within the pipe between the toilet and tub.

Clogged Vent Stack

A vent stack is the name of the pipe that is connected from the main drainpipe and runs throughout the roof of the house.

This pipe serves to remove any gasses from the main drainpipe in order to allow waste to flow easily down the drainpipe and into the sewer tank. 

If your vent stack has become blocked, then the sewer gasses are not easily able to flow out.

Thus, pressure begins to build up within the vent. As a result of this, whenever the tub is drained, water pressure forces the trapped gasses out through the toilet.

The water at the bottom of the bowl is intended to prevent sewer gasses from rising up into the bathroom.

However, due to the pressure and volume of draining a large amount of tub water, these trapped gasses breach this barrier, culminating in the bubbling/gurgling in the toilet.

Whilst a clogged vent stack results in issues with the sewer lines, a clogged main drain pipe is also problematic.

If you are dealing with a clogged main drain pipe, this means that waste is not able to freely flow out into the sewer lines and becomes accumulated in the pipe.

At first, your toilet may only bubble whenever you drain a large amount of water from the tub, however, this will exacerbate over time. As more and more waste accumulates, the pipe will run out of space and a backup will occur.

A backup occurs whenever sewage begins to emerge from your toilet or any other fixture. If you are also experiencing a partially clogged pipe, then a backup is unlikely to occur.

However, the toilet will continue to gurgle every time the tub is drained. 

Whether the clog is partial or not, you should still aim to fix it at the nearest given opportunity as this can develop into a larger blockage within a short period of time.

Fixing an issue like this earlier saves expense further down the line. This is because a toilet that is backed up will cost a vast amount of money to fix and you are less likely to be able to fix it yourself.

Thus, you will need to consult with a professional plumber and spend more than you would’ve initially needed to if you’d have fixed it at an earlier stage. 

Backed up sewage also causes a horrible odor that can permeate throughout the house. You may not even be able to stay in your house until the issue is resolved which causes further hassle and/or expense.

How To Fix A Toilet That Bubbles Whenever The Tub Drains

Why Does Your Toilet Bubble When The Bathtub Drains - An Easy Fix. (1)

Fortunately, there are several ways to fix a toilet that bubbles whenever the bathtub drains. As mentioned, the solution can be easy or incredibly expensive.

This will depend on the severity of the clog, the positioning, and whether the clog is material or not. 

The following methods are easy ways to fix a toilet that bubbles whenever the bathtub drains: 

1. Plunging The Tub

You should own a plunger if you have a bathtub in order to remove any blockages. In order to use this plunger to unclog your bathtub, you should remove the tub’s plug using a screwdriver.

Next, check if there are any blockages closer to the surface that can be easily removed as hair can often cause blockages. After this, cut a wire hanger and sculpt it into a hook using pliers.

Place this hook inside the drain and remove as many obstructions as you can.

Once you have done this, plug the overflow drain with a rag in order to avoid pressure loss, then, place the plunger around the drain and turn on the hot water until the plunger becomes immersed.

Finally, start plunging up and down above the water and hopefully the blockage will become dislodged.

After you have lifted off the plunger and allowed the water to drain, you should listen to hear if the bubbling from the toilet continues or not.

If it doesn’t, then you will need to purchase another tool or contact a plumbing professional. Using baking soda and vinegar is also a great way to avoid using harmful drain cleaners to unclog your drain. 

2. A Bathtub Snake

This is an instrument that contains a flexible cable, a handle and a hooked head. A bathtub snake directly impacts the clog inside of the pipe. These are easy to purchase or rent.

You should slowly insert the snake into the tub drain (see also ‘What To Do When Drain Snake Won’t Go Down Bathtub Drain‘) whilst cranking the handle in a clockwise direction.

Then, once you have encountered an obstruction, you should adjust the cranking direction before cranking once more in the prior direction until you have moved past the obstruction.

If you are unable to move past a certain point, then you should remove the snake and inspect whether you have pulled out any blockages.

The great thing about these snakes is that, because of their design, these clogs are able to be easily pulled and shredded.

3. Plunging The Toilet

Most people will use this method after noticing their toilet bubbling. This is because a toilet plunger is an essential household item that is incredibly useful to unblock clogs that are not too far out of reach.

These plungers are somewhat different from other forms of drain plungers as unlike other fixtures, the toilet bowl isn’t a flattened surface. This is why the most effective toilet plungers are often shaped like a bell. 

These specific toilet plungers will allow you to form an air-tight seal across the bowl which prevents any unwanted loss of pressure. 

4. Snake The Toilet

Similarly to how you would snake the bathtub, you can also snake the toilet. A toilet snake is otherwise known as an auger and is approximately 3-6 inches long.

This snake impacts directly on the clog by shredding it into smaller pieces or pulling it out.

These augers are far more powerful than their tub counterparts and thus, they are far more reliable and more easily able to remove blockages that are located further into the drainpipe.

Renting out a motorized toilet auger is also an option as these are able to remove far more stubborn blockages. These are able to be purchased or rented from most stores like Home Depot.

The only issue with using these toilet augers is that they can easily scratch the inside of the toilet bowl and leave unwanted marks.

5. Unclogging The Vent Stack

Prior to calling in a plumbing professional, you should make sure that you have not blocked the vent stack.

As the stack is typically left open at the top to allow for the gasses to flow out freely, it can become easily clogged by leaves or dead animals like small birds or rodents.

In order to ascertain whether the vent stack has become clogged, use a ladder to carefully climb onto the roof and inspect the condition of the vent stack.

If there is anything that you can easily remove from the stack using a wire or your hands, then remove these carefully, using gloves. After this, use a garden hose and pour water straight down the vent stack.

As the water builds up inside the vent, the weight of it will unblock whatever is clogging the drain and wash it away.

6. Call A Plumber

If you have tried all of the above methods to no avail, then you should contact a plumbing profession.

They will be able to easily ascertain what the issue is and solve it without causing any further damage. You should also always avoid opening the cleanup plug without having any plumbing experiences as this gives you open access to the drainage system.

If you remove this cleanup plug, then there is a likelihood that any sewage that is trapped inside will flow out forcefully and this will cause an even greater issue.


To conclude, if your toilet begins to bubble whenever the tub drains then you should act swiftly in order to prevent dealing with more costly repairs.

You should also ensure that you are removing any partial blockages and cleaning your drain pipes on a regular basis to prevent bigger issues from occurring.

Consult with members of your household to ensure that they are aware of what can clog a toilet or a bathtub (see also ‘ Why Does Water Back Up Into Your Tub? ‘).

Pouring hot water with baking soda and vinegar down household drains is also highly effective in treating blockages and preventing larger clogs from occurring. 

author avatar
Anthony Barnes
Anthony Barnes is the founder of Water Heater Hub and a second-generation plumber by profession. Before developing Water Heater Hub, Anthony Barnes was a full-time plumber, and he has undertaken a wide variety of projects over the decades. As a second-generation plumber, it was easy for Anthony to get used to the technicalities of all from a tender age


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Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases. When it comes to dealing with clogged drains, many homeowners turn