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Bathtub Gurgles When Toilet Flushes: A Comprehensive Analysis

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

Bathtub drains that gurgle when the toilet flushes can be an annoying and concerning issue for homeowners. The gurgling sound from the bathtub drain is often a result of trapped air, pressure difference, or clogging within the plumbing system. By understanding the potential causes behind this problem, you can take the necessary steps to address and rectify it.

There are several reasons why your bathtub drain might gurgle when you flush the toilet. One common cause is air trapped inside the pipes, which can be caused by blockages or pressure imbalances within the plumbing system. Additionally, issues with the P-trap or air being forced out of the drain can also contribute to the gurgling noise. This may require simple fixes such as plunging the toilet or more complex solutions like cleaning the vent stack.

By taking the time to assess your plumbing and drainage system, you can effectively identify the root cause of the gurgling noise and apply the appropriate solution. Following the necessary steps to address this issue will help you restore a quiet and efficient plumbing system in your home.

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Understanding Bathtub Gurgles

Plumbing System

A home’s plumbing system is an interconnected network of pipes, vents, and fixtures. The bathtub and toilet are often connected by a series of pipes, with vents allowing proper air circulation. This integration is crucial to maintain water flow and prevent pressure build-up within the system.

Gurgling Noise Explained

A gurgling noise in the bathtub when the toilet is flushed is typically caused by air being forced through the pipes due to a pressure difference. This can be a result of trapped air, a clogged vent stack, or blocked pipes. The vents play a crucial role in ensuring that the pressure is balanced, enabling smooth functioning of the plumbing system.

Venting System

The venting system in your plumbing is designed to regulate air pressure and release sewer gases outside the house, ensuring proper water flow. When the vent is clogged by debris, such as leaves or bird nests, the system becomes disturbed, which may cause bathtub gurgles when the toilet flushes. Routinely cleaning the vent screen or using a sewer auger can help solve the issue.

Pressure Difference

When there is a significant pressure difference in the pipes, the trapped air or water may cause the bathtub drain to gurgle. Factors contributing to this pressure difference include:

  • Clogged pipes: Dirt and debris can build up in the pipes, leading to a pressure imbalance.
  • Pipe diameter: Smaller pipe diameters might restrict water flow, contributing to pressure changes.
  • Improperly installed plumbing system: If the plumbing system, specifically the vents, is not installed correctly, it can lead to persistent gurgling noises.

Addressing these issues can help prevent unwanted gurgling noises in your bathtub when the toilet is flushed.

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Common Causes of Gurgling

Clogs and Blockages

Bathtub gurgles when the toilet is flushed can often be caused by clogs and blockages in the plumbing system. Debris, such as hair or soap scum, can accumulate in the pipes, leading to restricted water flow. If the water cannot move freely through the pipe, it may create a gurgling sound as the air is forced through the blockage.

To fix this issue, you can try removing the debris manually or using a chemical drain cleaner. A garden hose can also be helpful in dislodging blockages from the overflow drain. Make sure to address clogs promptly, as they can lead to more severe clogging issues over time.

Vent Stack Issues

Another common cause of gurgling sounds in your bathtub is a clogged vent stack. The vent stack is an essential part of the plumbing system that allows air to escape, preventing a vacuum from forming in the pipes. When a vent stack becomes blocked, trapped air may cause gurgling sounds when the toilet is flushed.

Cleaning the vent screen or using a sewer auger can often solve vent stack issues. Make sure to check your vent stack regularly for any signs of blockage, as this can lead to more significant plumbing issues if left unaddressed. For more information, visit this guide on vent stack cleaning.

Improper Venting

Lastly, improper venting can lead to gurgling sounds when you flush the toilet. If the plumbing system is not vented correctly, it may cause air pressure imbalances within the pipes, leading to gurgling noises. In some cases, the venting system can be too narrow, limiting the amount of air that can pass through and causing gurgling sounds.

To fix the issue, consider having a professional plumber inspect your venting system and make any necessary adjustments. This may include increasing the diameter of the pipe or ensuring proper vent placement. For a thorough analysis of your venting system, refer to this guide on bathtub drain gurgling noises.

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Identifying the Problem Source

Gurgling Toilet

A gurgling toilet is generally a sign of a blockage or an issue with the venting system. This can be caused by several factors, including a buildup of debris or an obstruction in the drain or vent pipe. When the toilet is flushed, air pressure in the pipes creates a gurgling noise as it tries to escape the pipe. In order to resolve the issue, it’s essential to identify the cause and consider methods such as using a plumber’s auger or addressing vent system concerns.

Gurgling Bathtub Drain

A gurgling bathtub drain typically occurs because of trapped air in the pipes, issues with the P-trap, or air escaping through the drain. A common sign of an issue with the P-trap is when water level in the toilet bowl fluctuates when the bathtub drain gurgles. In such cases, one might have to inspect and clear the P-trap. If air is trapped inside the pipes, plunging the toilet can help release the air, thus resolving the gurgling sound in the bathtub drain.

Sink Gurgles

Similar to a gurgling bathtub drain, a gurgling sink may also indicate problems with the venting system or a clogged drain. In particular, air coming out of the drain can cause the gurgling sound in the sink. A few possible solutions include:

  • Plunging the sink to help release trapped air or clear soft clogs.
  • Inspecting the sink drain and P-trap for any blockages and cleaning them as necessary.
  • Checking the vent pipe for any obstructions and clearing them if needed.

By identifying and addressing the root cause of the gurgling noises, you can maintain a properly functioning plumbing system in your home.

Effective Solutions for Gurgling Drains

Using a Plunger

A simple and effective solution to clear gurgling drains is plunging the toilet. This method helps to remove trapped air in the pipes. Start by duct taping the drains shut, including the shower drain, sink drain, and overflow drains. Then, use a plunger to create pressure and dislodge blockages responsible for the gurgling noise1.

Applying Baking Soda and Vinegar

This natural solution is a great alternative to using harsh chemicals. To unclog the drain and clear trapped air, follow these steps:

  1. Pour 1 cup of baking soda down the drain.
  2. Wait for about 5 minutes.
  3. Pour 1 cup of white vinegar down the drain and cover with a drain plug.
  4. Let the solution sit for 15-30 minutes.
  5. Remove the plug and flush the drain with hot water2.

The combination of baking soda and vinegar will help break down the clog and eliminate the gurgling noise.

FAQs of Plumbing Snakes

Employing a Plumbing Snake

A plumbing snake is a flexible, hand-cranked tool that can be fed into the drain to reach and remove clogs. It is especially effective for more stubborn, deep-set blockages. Carefully insert the snake into the drain, and slowly crank the handle to push it through the pipes. Once the clog is dislodged, retract the snake and rinse the drain with hot water.

Using a Sewer Auger

A sewer auger is a heavy-duty version of a plumbing snake that can handle larger blockages and reach farther into the main sewer line. This powerful tool is best used when other methods have been unsuccessful. Employing a sewer auger usually requires professional assistance to ensure safe and proper use.

By employing these effective solutions and employing proper plumbing maintenance, you can effectively address gurgling drains and keep your pipes in optimal condition.

When to Call a Professional Plumber

Sometimes, simple DIY solutions may not be enough to fix the issue of bathtub gurgling when the toilet is flushed. In such cases, it’s important to know when to call a professional plumber to identify and resolve the problem efficiently. This section covers a few scenarios when seeking professional help is necessary.

Persistent Blockages

If you’ve tried common solutions like plunging and using drain cleaners, but the gurgling persists, it could indicate a more complex blockage in the pipe system. A licensed plumber can locate and remove blockages that may be too deep for standard household tools to reach. These professionals have the necessary tools and expertise to remove persistent blockages without causing damage to your plumbing system.

Excessive Gurgling

When the gurgling is unusually loud or frequent, it might be a sign of a more significant issue with your plumbing system. A professional plumber can inspect and identify any underlying problems, such as issues with the venting system, which requires specialized knowledge to address. In these cases, attempting to fix it yourself without proper understanding may even make the problem worse.

Septic Tank Issues

If you have a septic system, gurgling noises from your bathtub drain may signify problems with the tank or its drainage field. Septic tank issues should always be handled by a licensed plumber since dealing with septic tanks requires specific expertise and knowledge to avoid health hazards and environmental contamination.

Remember, when faced with persistent blockages, excessive gurgling, or septic tank issues, contacting a professional plumber is the best course of action to ensure that your plumbing system is fixed safely and efficiently. It’s always better to err on the side of caution and seek professional help to maintain the integrity of your plumbing system.


Preventative Measures

To avoid bathtub gurgles when the toilet flushes, it’s essential to take some preventative measures. These steps will ensure that your plumbing system remains in good condition and functions efficiently.

Regular Plumbing Maintenance

Regular plumbing maintenance is crucial to prevent clogs and air blockages that cause gurgling sounds. Inspect and clean your pipes periodically, and as needed, use a plunger to remove trapped air in the plumbing system. It’s also a good idea to check your vent stacks for blockages, as these can affect the airflow through your pipes. If necessary, clear your roof vents or hire a professional to do so.

Proper Disposal of Debris

Proper waste disposal plays a significant role in preventing bathtub gurgles. Avoid flushing items such as:

  • Thick toilet paper
  • Wet wipes (even those labeled as flushable)
  • Feminine hygiene products
  • Diapers

These materials can cause clogs that lead to trapped air, increasing the likelihood of gurgling sounds. Instead, dispose of them in a trash bin to help maintain proper airflow through your plumbing system.

Installing Vent Pipes Properly

Ensuring that your vent pipes are correctly installed will minimize the risk of gurgling sounds in your bathtub. Vent pipes are essential for controlling the air pressure in your plumbing system and preventing air from being trapped. If you suspect that your vent pipes are not installed properly or if they are clogged, consult a professional plumber for assistance. They can assess the situation, identify the problem, and recommend a suitable solution.

By following these preventative measures, you can maintain a smooth and functional plumbing system, reducing the likelihood of bathtub gurgles when your toilet is flushed.


A bathtub drain that gurgles when the toilet is flushed can be an annoying issue, but fortunately, it’s often relatively easy to diagnose and address. The main cause of this problem is usually a clogged vent stack, which prevents air from properly flowing within the pipes, leading to the gurgling sound. To fix this, cleaning the vent screen or using a sewer auger can help resolve the issue.

If the vents are clear, another possible cause might be a soft clog in the toilet drain. In such cases, using a plunger for a few rounds could help remove the clog and stop the gurgling sound. Addressing these issues not only eliminates the noise but also ensures proper airflow and smooth drainage in the plumbing system.

Sometimes, the issue might persist even after addressing aforementioned possible causes. In such cases, it’s important to seek professional help from a licensed plumber to identify any underlying issues and provide an appropriate solution.

By taking prompt action to address bathtub gurgling, homeowners can prevent potential damage to their plumbing system and maintain a properly functioning bathroom.

Frequently Asked Questions

Why does my tub drain gurgle when I flush the toilet?

The gurgling sound often occurs due to trapped air in the pipes. A bathtub piping system has air vents that control the amount of air in the pipes, which can sometimes get blocked by dirt and debris. When the toilet is flushed, the water movement creates pressure differences in the pipes resulting in the gurgling sound.

How can I fix a slow flushing toilet that gurgles?

To fix a slow flushing toilet that gurgles, you can start by plunging the toilet to remove any trapped air and potential blockages. Plunge the trapped air out of the drain with a toilet plunger, ensuring a proper seal is created for maximum effectiveness.

What causes drains to make noise when the toilet is flushed?

Noisy drains are often caused by trapped air, clogs, or vent blockages that create pressure differences when water flows through the pipes. The pressure difference causes water or air to be forced through the openings, resulting in the gurgling or bubbling noises.

How can I prevent water from filling the bathtub when I flush?

To prevent water from filling the bathtub when you flush, ensure the piping system is free of blockages and is properly vented. Regular maintenance and cleaning of your drainage system will help keep water flowing smoothly and prevent backups or filling of the bathtub.

How to fix a gurgling shower drain?

To fix a gurgling shower drain, start by sealing all nearby drains with duct tape to create an airtight seal. Then, use a plunger on the shower drain to remove trapped air or unclog any debris within the pipes. You can also check for proper venting and clear any obstructions found in the vent system.

Is there a connection between shower gurgling and toilet flushing?

Yes, there is often a connection between shower gurgling and toilet flushing. Both are related to the air and water pressure in the plumbing system. When the toilet is flushed, it creates pressure differences in the pipes, which can lead to gurgling noises in other parts of the system, such as the shower drain. Ensuring a well-maintained and vented piping system will help prevent gurgling noises and maintain smooth water flow.


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