Why Your Toilet is Gurgling and How to Fix It Quickly!

What Causes a Gurgling Sound in Toilet?

A gurgling toilet is caused by negative air pressure in the drain line. That happens when the drain line, sewer line or plumbing vent is clogged resulting in suction/siphoning of water from the bottom of the toilet. Sometimes you will also notice the toilet bubbling after being flushing.

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A gurgling toilet is usually a sign of a serious problem in the plumbing system. If the sewer line or drain line is clogged, it will be a matter of time before sewage starts to backup from the toilet. On the other hand, a clogged plumbing vent causes slow drains and a sewer smell in the house.

To fix a gurgling toilet. determine first if you are dealing with a clogged drain line, sewer line or plumbing vent. Once you identify where the problem is, go ahead and unclog the clogged pipe. A drain snake can unclog both the drain and the vent stack. Sewer line may need a pro.

A gurgling toilet will hardly fix itself. You will need to unclog the toilet drain line if that is the problem or climb to the roof of the house and unblock the vent stack. At times you may need to bring a plumber to inspect and fix the sewer line.

For those who are not familiar with the terminologies, I would like to differentiate between drain line, main line and sewer line.

A drain line is the pipe which carries wastewater from a single fixture. This means that each toilet, sink, shower, tub and washing machine has a separate drain line.

The main line on the other hand is the pipe which where all the drain lines in the house are connected to. It is also called the drain stack and it is also where the vent stack is connected to.

The sewer line (which some people sometimes call the main line) is the pipe installed in your yard (underground) and which carries wastewater from the entire house to the city sewer line near the street or to the septic tank.

Toilet Gurgles When It Rains?

In some instances, toilet do not gurgle because any of the pipes in the drain-waste-vent system is clogged, but because of rain water. But how does rain cause a toilet to gurgle?

If your drain gurgles when it rains, it is a sign that rain water is entering the drainage system. The increased volume of water overwhelms your drain line resulting in a gurgling toilet as the water forces its way out of the small pipe.

This problem could be restricted to your house only but it could also affect an entire neighborhood if storm runoff is entering the city sewer lines.

The first thing you should do therefore is to contact your neighbors and check if they are having the same problem as yourself.

If the problem is spread throughout the neighborhood, contact you city water department immediately and let them know of the problem. That is their problem to fix.

Contact a plumber (at your own bill) if the problem is restricted to your house. Your sewer line could have a crack allowing surface run off into the drainage system which overloads the system resulting in a gurgling toilet.

Please remember that the city is responsible when the problem is in the public sewer line along the street. The sewer line between your house and the street is strictly your responsibility.

Troubleshooting a Gurgling Toilet

As you already know, there is always water at the bottom of the toilet. What you may not know is why the water is there.

The water at the bottom of the bottom of the toilet bowl (in the toilet trap) act as a barrier preventing sewer gases from coming up through the toilet drain. Every fixture in your house that is connected to the sewer line has a drain trap.

You can see it (U-shape bend) under your kitchen or bathroom sink. Instead of sewer gases coming up through the drains, it is forced out through the plumbing vent which runs through the roof of the house.

If the plumbing vent is clogged, there will be nowhere for the sewer gases to flow out through so they will be trapped inside the drain lines creating an air lock.

The sewer gases will try to force their way out through the toilet trap or any other drain trap but since there is water, the interaction between the gases and water will result in the gurgling sound.

A clogged plumbing vent will affect all other fixture drains in your house and not just that toilet. Some of the other signs that you have a clogged plumbing vent are:

So, how does a clogged plumbing vent create negative air pressure inside the drain lines?

Remember, apart from removing sewer gases from the drain line, a vent is also responsible for introducing air into the drainage system to help fixtures drain fast and toilets flush better.

When the vent stack is clogged, that will not happen.

If for instance you drain the bathtub or washing machine or even flush the toilet, the column of wastewater as it flows down the drain line will create a vacuum inside the drain lines. And that is what is known as negative air pressure

Negative air pressure basically means that the air pressure in the surrounding (atmospheric pressure) is higher than the pressure in the drain lines.

The only thing separating the 2 imbalanced pressures is the water in the drain traps. In a bid to create a balance, the vacuum in the drain line will siphon the water from the toilet trap and hence the gurgling sound.

If the water in the shower, sink or washing machine traps is siphoned out, the barrier created by it will have been broken and you will experience a sewer smell in the house.

plumbing-vent-diagram
Image Credit: NextDay Inspect

As I have already mentioned, a clogged toilet drain line will also cause the toilet to gurgle. How does that happen?

With a clogged toilet drain line, wastewater does not flow out to the sewer line. Instead, it accumulates inside the drain line.

As such, there will be trapped air between the top of the wastewater and the water barrier created by the toilet trap.

As more wastewater is deposited, the air pressure will increase forcing its way through the toilet trap and hence the gurgling sound.

If this problem is not fixed early enough, you will have sewage backing up through the toilet.

How to Fix a Gurgling Toilet

From the above, it is easy to know if your gurgling toilet is caused by a clogged drain line or vent stack. With that information in mind, you can easily fix the toilet and stop the gurgling.

1. Plunge the Toilet

In most cases, a clogged toilet drain line is caused by toilet paper which is fairly easy to dislodge using a toilet plunger.

The first step of successful plunging is in the choice of plunger. The best toilet plunger is what is known as a flange plunger.

A flange plunger is usually designed to fit in the opening at the bottom of the toilet bowl therefore creating a watertight seal. Flat-bottomed plungers should only be used to unclog other types of drains like sinks and tubs.

Also, you should have enough water in the bowl if you are to clear a clog using a plunger. Ideally, the rubber part of the plunger should be immersed in the water.

Place the plunger around the opening at the bottom of the bowl and start plunging gently. Gentle plunges in the beginning help the plunger seal properly on the toilet and also prevent water from splashing on you.

  • Once the plunger is properly engaged to the toilet, plunge aggressively for a few minutes.
  • Lift off the plunger and flush the toilet.
  • Carefully listen if the gurgling sound has stopped.
  • Plunge some more if the gurgling persists.

2. Snake the Toilet

If you didn’t have success plunging the toilet, snaking could do the trick. A toilet auger or a plumbing snake will either break down the clog into tiny pieces or hook it and pull it to the surface.

The one thing you need to be careful about when using a toilet auger is scratching the toilet bowl.

A toilet auger consists of a hooked head, a flexible cable and a cranking handle. Luckily, the auger has a guard which allows you to safely introduce and pull the snake from the toilet drain without scratching the bowl.

Here is how to unclog a toilet using a toilet auger:

  • Pull the cable inside the tube so that the auger head is firmly held at the bowl guard.
  • Careful introduce the tube inside the bowl and place the bowl guard at the opening with the auger head already inside the trap.
  • Slowly start pushing the cable down the toilet drain until you encounter resistance.
  • Start turning the handle clockwise. Remember that the cable should turn with the handle but not twist. If it starts to twist, change the direction of turning pull it out a little bit then start again.
  • Keep turning the handle until you go past the restriction. Go further down to make sure there are no more clogs.
  • When pulling out the cable, you need to be careful so that you don’t scratch the bowl. Place the tube and bowl guard at the bottom of the bowl and slowly pull out the cable.
  • When the auger head is held on the bowl guard, carefully lift out the tube without making contact with the inside of the bowl.
  • Check if the gurgling has stopped by flushing the toilet.
  • Clean the auger and store it.

3. Unclog the Plumbing Vent

You can easily unclog a plumbing vent if you can manage to climb to the roof of the house. You will need a ladder, a garden hose and sometimes a drain snake.

Here is how to unclog a plumbing vent:

  • Climb to the roof of your house armed with a garden hose.
  • Check if there are blockages at the top of the vent stack which you can easily remove with your hand.
  • Stick the garden hose inside the vent stack and use it to probe and hopefully dislodge whatever that is clogging it.
  • Have someone on the ground turn on water to the hose. The weight of the water maybe enough to clear the clog. If it is snowing, dump boiling water inside the vent. Snow is known to clog vents.
  • If the clog won’t just budge, you can upgrade to a plumbing snake. Not toilet auger.
  • Push the snake inside the vent pipe until you encounter the clog resistance.
  • Turn the handle until you move past the resistance then go deeper to make sure there is no another clog.
  • Have someone again flush the toilet and confirm that the gurgling has stopped.

4. Unclog the Sewer Line

Sewer line inspection

As I have already mentioned, a clogged sewer line will affect all drains and not just the toilet. This is because your house has only one sewer line and many fixtures connected to it.

A sewer line is however one of those areas where I don’t recommend DIYs. It is a sensitive area and should be left to professional plumbers.

As I had mentioned already, a cracked sewer line could be bringing in rain water and hence a gurgling sound in the toilet. Only a plumber can fix that.

A licensed plumber will first use a sewer inspection camera to check if your sewer line is clogged and if so where the clog is and what type of clog it is. They will also be able to see the status of the sewer line and advise you on what is the best solution.

If you however what to give it a shot yourself, you will need to rent a motorized drain snake from a plumbing store then locate your sewer cleanout.

A sewer cleanout allows you access to the sewer line but if you do not have one you will need to do it from the vent stack or pull out the toilet.

Be careful when removing the sewer cleanout plug as raw sewage may spill out. Again, this is why I recommend letting the pros take care of sewer lines.

Wrap Up

And basically that us why have a gurgling toilet and the steps you can take to fix it. I hope this guide was helpful.

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