Why Is My Toilet Gurgling?

A toilet in a black and white bathroom

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The toilet is one of the most frequently used plumbing fixtures in the home, so when problems occur, it's important to quickly investigate the issue to determine what could be causing the toilet to sound odd or function incorrectly. If the situation is left unresolved, it could lead to more serious problems, like leaking drain lines, water damage, and mold or mildew growth.

Typically, air can flow freely through the lines, allowing waste to run smoothly down and out of the home, but when a toilet makes a gurgling noise, this is a sign that negative air pressure or suction is building up in the drain line. Eventually, the negative air pressure releases, pushing air back up through the drain and into the toilet bowl, causing the gurgling sound. When this occurs, the toilet may also bubble and flush itself.

Fixing this issue should be a high priority. While the gurgling may be easy to ignore, if the cause of the negative pressure is a broken or collapsed drain line, the problem can get worse, resulting in backed up toilets, showers, sink, and tub drains. Use this guide to figure out why your toilet is gurgling and what to do about it.

Blocked Vent Pipe

The drain lines that run throughout the home don't just run down to the main drain stack, they also include vent pipes that typically exit through the roof of the home. Vent lines are intended to release exhaust gas from decomposing waste and to allow pressure to escape from the plumbing system. However, if the vent pipe is clogged, the pressure cannot escape the drain lines, restricting airflow, and causing the toilet to gurgle.

Clogs that are near the top of the vent pipe can be pulled out with a hooked drain snake, while blockages that are deeper down the line may need to be broken up by using a garden hose to introduce water to the line and an auger drain snake to break up the clog. If you are comfortable with working on the roof, you can attempt to locate and dislodge the blockage on your own, but in most cases, it's better to entrust this task to a trained professional.

Clogged Toilet

One of the more common reasons for a toilet to start gurgling is a clog in the toilet's drain line. The blockage can impede the flow of waste and air, causing negative pressure to build up in the drainpipe and producing a gurgling sound or even bubbles in the toilet water as air slowly escapes. Toilet clogs can be a result of too much toilet paper, a large amount of waste, or other objects that are not intended to be flushed, like wipes, feminine hygiene products, or cotton balls.

This issue can usually be resolved with nothing more than a plunger. Simply fit the head of the plunger tightly to the drain hole in the toilet, then try to dislodge the clog by pumping the plunger about 10 to 15 times. After plunging the toilet, flush the toilet and wait to see if it still gurgles. If the toilet still gurgles, you may need to insert a drain snake into the toilet drain to physically break up the clog.

Main Sewer Drain Line Clog

In some cases, the blockage that is causing negative pressure to build up is located further away from the gurgling toilet, so a plunger won't be effective at dislodging the blockage. Instead, you will need to try to pull out the clog or break up the blockage with a drain snake.

A manual drain snake with an auger head and a long, 15- to 25-foot metal line can be slowly introduced into the drainpipe by turning the auger crank. In some instances, the clog is too deep, even for a manual snake, so you will need to purchase or rent a motorized drain snake.

Motorized drain snakes usually have a length of 100 feet or more, so you shouldn't have trouble reaching the clog. It's recommended to remove the toilet from its base before attempting to use a motorized snake in order to avoid damaging the toilet. However, unless you have significant experience using these tools, it's recommended to call in a professional plumber to clear the clog.

Exterior Sewer Line Blockage

A gurgling toilet typically indicates a problem with the interior plumbing of the home, but this isn't the only location where a blockage could create issues. The exterior sewer line of the home may also be responsible for the gurgling sound. This could be caused by the drainpipe collapsing, dirt entering the line and creating a clog, or even nearby tree roots rupturing the drain line.

You can attempt to solve this problem on your own with a motorized drain snake to try to clear out the drain line. Insert the drain snake into the drain line from the main sewer clean out, instead of entering through the toilet drain. Just keep in mind that even if the drain snake reaches the clog, you may not be able to break through depending on the nature of the clog. If you suspect the issue is a blocked exterior sewer line, it's recommended to hire a professional plumber to resolve this problem.

Municipal Sewer Main Problem

There are rare instances where a gurgling toilet can be traced back to problems with the municipal sewer main. Before contacting the municipality, it's a good idea to speak to your neighbors to find out if they are experiencing the same problems. Unfortunately, in these cases, there isn't a lot you can do to fix the issue beyond contacting the municipality to inform them of the problem. Keep in mind that municipality workers are more likely to inspect and resolve the situation quickly if it is impacting more than one household.