Why Your Toilet Bubbles When Flushed – Causes and Fixes

Does your toilet bubble or gurgle when flushed? While it may not seem like a critical problem, it is a sign that something is wrong with your plumbing system, and it needs to be fixed. I talked to two licensed plumbers, Alexander Siv and Jason Duda, to help explain the causes of a bubbling toilet, when you can fix it yourself and when to call in a pro to remedy this puzzling plumbing issue.

Why Do You Get Toilet Bubbles When Flushed?

“A gurgling toilet usually means there’s a clog in the drain line or there’s an issue with the plumbing venting system,” Duda says. “There’s not enough air in the system, so when the water goes down the drain, it’s sort of gulping for air as it goes.”

What Are the Causes of Bubbles in Toilets?

Here are some situations that can cause a toilet to bubble when flushed, as well as ways to fix each issue.

Clogged toilet

A clog in the toilet’s trapway (the curved part of the toilet base near the back) is one of the more common causes of bubbling or gurgling. It can be the first place clogs occur due to excessive toilet paper, solid waste or flushed non-biodegradable paper products.

Clogged vent pipe

Every plumbing fixture, including toilets, is connected to a vent pipe that extends through the roof and provides air to the drainage system. If these vents become clogged, you’ve got a problem.

“[Vents] provide air to the drainage system and allow the water to go down the pipes,” Duda says. “If the vent pipe is blocked or clogged, this can lead to gurgling or bubbling in the toilet.”

Outside, vent pipes can get clogged with bird nests or debris from hanging branches. Inside the home, a blocked drain line can redirect flushed paper up into the vent pipe, causing a clog. This is a common issue Siv encounters. “The water recedes and the paper hardens in the vent,” he explains. “Even a partial block will restrict the airflow and can lead to a gurgling toilet.”

Blocked drain line

Clogs in nearby shower or tub drains can also cause bubbles in the toilet when a toilet is flushed. “This is more likely if the clog is located near the drain vent and is blocking air flow,” Siv says. This can lead to the system pulling air from the toilet bowl, causing bubbling. A clogged drain line can also trap air in the system that will escape out of the toilet bowl and cause bubbling.

Clogged sewer line

A clog or partial blockage in the main sewer line can also cause air to become trapped in the pipes. When you flush a toilet, the trapped air can create bubbles or gurgling sounds in the toilet bowl.

Other signs that indicate a block in the sewer line are a foul smell in your bathroom or if flushing one toilet causes another to bubble. “If you’ve got a toilet that is gurgling, you might have other fixtures that are gurgling, which can point to a sewer line issue,” Duda says. You also have to check your septic tank gurgling. There can be a microbial issue or a septic tank related problem.

Sewer lines can become blocked by tree roots, a damaged pipe or debris buildup.

How to Fix a Bubbling Toilet

In some cases, you can fix a bubbling toilet yourself. However, there are certain situations where you’ll need to call a professional plumber.

Clogged toilet

The fix for this is usually DIYable. Position a toilet plunger over the toilet bowl outlet and do 10 to 15 vigorous plunges. If the clog is in the trapway or anywhere near the toilet itself, this should dislodge the clog and solve your problem.

If a plunger doesn’t work, try a toilet auger. Wearing protective gloves, insert the auger end into the toilet bowl and into the drain pipe without scratching the porcelain. Turn the auger until you hit pressure, then retract the auger line and (hopefully) your clog.

Clogged vent pipe

You’ll likely need a pro to fix a clogged vent pipe. Pros send a camera down into the vent pipe from the roof to locate the clog. Then they use a drain auger or snake to remove the blockage.

“If I can see it on the camera, I can normally get it with the snake,” Siv says. If not, this means the clog is in a horizontal pipe behind a wall. To find and fix these clogs, he cuts an access hole in the wall to gain entry to the pipe.

If you want to try to unclog your vent pipe yourself, get a length of rope, a thin flashlight and duct tape. Wear rubber-soled shoes and plan to do the work when your roof is dry. Locate your vent pipe and carefully climb up to your roof on a properly secured ladder and wearing a roof safety harness. Tie and tape the flashlight to the rope, then lower it into the pipe.

Look for debris and use a drum auger to retrieve the blockage. Send the tip of the end of the flexible wire into the pipe and turn the crank handle each time you extend more wire. If you hit resistance, turn the handle a few times to break up the blockage, then retrieve the wire (and blockage) from the pipe. When finished, pour water down the vent to clear any remaining debris.

If your roof is steeply pitched or more than 12 feet from the roof edge to the ground, stay safe and hire a pro.

Blocked drain line

The fix for this is to use a plunger or drum auger to remove the clog in a nearby shower or tub drain.

Clogged sewer line

“It’s a good idea to call a drain cleaning company and have them snake out the lines,” Duda says. Sewer and drain professionals use cameras and extended electric augers to remove the clog. If the problem is tree roots or a damaged pipe, a pro can diagnose and repair the problem.

Tips to Prevent Bubbling Toilets

• Address minor clogs promptly. Unclog a slow-draining toilet promptly to prevent bigger backups.
• Flush only toilet paper and solids. Avoid flushing sanitary products, baby wipes and tissues as these are not intended for use in a toilet and can cause clogs.
• Trim back overhanging branches. Prevent debris from making its way into vent pipes and creating a clog. If trimming isn’t possible, consider placing a vent pipe screen to keep out debris.

About The Expert

• Alexander Siv is the owner of Amherst Heating and Plumbing in Amherst, Massachusetts. He has a master plumbers license in Massachusetts and has more than 10 years of experience.
• Jason Duda is the manager of Boulanger’s Plumbing and Heating in Easthampton, Massachusetts. He holds a master plumbers license in Massachusetts, Connecticut, New York and Virginia with 25 years of plumbing experience.

FAQ

What does it mean when your toilet bubbles after you flush?

Toilet bubbling or gurgling generally indicates a problem in your plumbing system. If you see this phenomenon after flushing your toilet, it could be a sign of a clog. There may be a blocked drain line or vent pipe. Also, there can be an obstruction in the main sewer line. Due to this, air can’t flow properly through the pipes. It creates the bubbling effect in your toilet.

How do I fix a bubbling toilet?

You can first try to fix this on your own. Use a plunger. It will help you to dislodge the clogs. If that doesn’t work, you can also use a toilet auger. It may reach and clean deeper clogs. Also, you should try the hot water with dish soap method. It will soften blockages. If the clogs still remain there, the issue may be bigger. It may be related to a deeper problem. So, it is better to get the help of a professional plumber.

Can a septic tank problem make my toilet bubble?

Yes, your septic tank can make your toilet bubble. You can see the septic tank gurgling as well. You need to check whether your septic tank is full, clogged, or malfunctioning. It can be the reason for the bubbling toilets, foul odors and slow drains. It also traps air in the plumbing system. You need a quality septic inspection and pumping for this.

What tools can I use to clear a clogged toilet vent?

Some modern and effective tools can easily clear your clogged toilet vent. Mainly DIYers use these tools. A flashlight and rope can be helpful to inspect the vent. Drain or drum augers are for the blockages. Also, you may need duct tape for leaks. You may need a garden hose to clear out the debris. If you are doing this on your own, always wear safety gear and take safety measures.

Sources:

• NLM: “Aerosol Generation by Modern Flush Toilets”
• Nature: “Particle exposure risk to a lavatory user after flushing a squat toilet”
• NLM: “Reducing the particles generated by flushing institutional toilets”
• Taylor & Francis Online: “Clogging potential of low-flush toilet branch drain system”
• NSDU: “Check Your Sewer Vents”
• ScienceDirect: “Building water quality deterioration during water supply restoration after interruption: Influences of premise plumbing configuration”
• ARIC Journal: “Bioaerosol concentrations generated from toilet flushing in a hospital-based patient care setting”