Bathtub Drain Gurgles When Toilet Is Flushed

How To Stop Bathtub Drain Gurgles When Toilet Is Flushed?

Is your bathtub drain gurgling when the toilet is being flushed?

Not only is it annoying but also concerning as there could be a major underlying problem. You might have to get some parts replaced or repaired that could be expensive.

However, you don’t need to panic yet, because there are some simple fixes that can help you solve the problem instantly.

We will guide you through all the different reasons why the bathtub drain is gurgling and some of the ways to fix it. These are easy ways and you can try these yourself or with some help. Keep reading to find out!

How does the plumbing system work?

Before trying to fix the problem and trying to find a solution, you will need to make sure that you have a piece of basic plumbing knowledge.

A typical residential pumping system consists of 4 parts: waste drains, waste vents, and a rainwater management system. For now, we will focus on the first two components.

  • West drains carry down wastewater

All our home fixtures are connected to a large drainage pipe via small pipes of different sizes like the bathtub as well as the toilet.

The wastewater that flows down the drains by gravity keeps flowing until it reaches the septic tank or the municipal drainage system, whatever your house drains are connected to.

  • Waste vents regulate air pressure

When you flush your toilet, the front air is pushed out by the water down with it. If the pipes were a vacuum, they would be crushed by external atmospheric pressure. To prevent that, the waste drains are connected to a very large vent stack that usually sticks out of your roof. Thus, when the water flows down the drain, equal amount of air flows from the vent to equalise the pressure after the water has flowed out.

These vents also help in releasing the sewage gases that normally build up in the main pipe.

  • The P-trap

If you look under your sink, you will find a u-shaped part that is called the P- trap. This part helps in preventing the smell from coming back into your toilet and drains. The lower dip of this part holds water and that prevents the gases from flowing into your house back again.

How to prevent the bathtub drain gurgles when toilet is flushed?

  • Check If your drains are clogged: As already mentioned previously when we flush our toilet, to maintain the pressure inside the pipes, some air replaces the flowing water. This air comes from the roof vent.

When this air vent gets clogged, no more air can flow inside it. Now there are two possibilities.

  • No air is able to flow and a vacuum is formed inside it. If enough extreme physical conditions were present, your pipes would instantly be crushed by external pressure.
  • The second possibility is that the air will be sucked inside the pipe through the nearest fixture which is the bathtub in this case.

The gurgling sound happens because the air was trying to enter from the same place where the water was pouring.

To fix this, you need to clear your venting system by removing the clogs which can get a little tricky. The vent stack runs through the whole length of your house and the clog could be anywhere along the way.

If your vent stack is covered by a screen, you will most likely find the screen holes that are completely obstructed by dirt. Clean the screen and the problem would be resolved.

If even that doesn’t work, it means that the clog is located much deeper than you can see. Start spraying some water with your garden hose which will push the clog down the drain and clean the system. You can also use a sewer auger to mechanically push the clog along with the water.

  • Maybe the drain pipes are too narrow: As we’ve seen before, the air flowing through your bathtub is to compensate for the clogged vent. However, sometimes, the vent is clear but the sink still gurgles.  This is because the air isn’t entering the pipes anymore, it is actually coming out.

After you flush the toilet, the water pushes the airstream down and if the pressure builds up too much the air finds it easier to come out through the nearest fixture.

There could be a lot of reasons that could cause the sound. It could be because your toilet may be flushing more water than the pipes can handle.

Putting a brick in the toilet tank is the easiest way to solve this issue.

However, if the problem has developed recently then the waste pipes are to be blamed. Some of the waste gets stuck over the pipe walls. As time goes by, the waste starts to decompose and harden. It doesn’t directly clock the pipes but it makes them narrower. So when even a small amount of water flows in it, the pressure builds and the air gurgles in your bathtub.

You can use a plunger to push some of the waste to widen the pipes. Repeat it for 3 to 4 rounds to see if it’s working.

If that doesn’t work, you can use a toilet auger that shares the same principle as that of a regular drain auger but is equipped with a longer arm to drive the wire deeper.

  • Check your bathtub P-trap: If none of the above methods works, it might be that your bathtub’s P-trap has become rusty and started to leak. If that is the case, the gurgling will be followed by water leaking from the roof or walls beneath your bathtub.

If you find that your bathtub drain smells awful it could mean that the P-trap can’t hold the water in its dip which allows the sewer smell back up from the drain. You can call for the plumber to fix the faulty P-trap in no time.

  • Use a coat hanger to remove the clogs near the drain: It may seem a little strange but a coat hanger can be very helpful to remove the clogs.

Straighten the hanger and cover the end using a spare piece of cloth to prevent it from damaging the toilet’s porcelain. Then guide the wrapped straightened hanger down the drain until the obstruction is reached. Twist the hanger severally to break the clock and remove it.

Now, flush the toilet to push the clog down the drain to the sewer. This method only works for the clogs that are near reached. You will need a longer plumbing snake for the ones that are even harder to reach.

  • Replace old cast iron pipes: Before ABS or PVC pipes, cast iron was widely used in plumbing systems.

Cast iron has a high tendency of corrosion and also, the rough surfaces of the corroded pipes can cause more waste and minerals to precipitate on them. This leads to narrow pipes and as we already know narrow pipes build up air pressure as water flows. This makes the air escape through the drain which in turn produces the annoying gurgles.

Fixing these require certain technical skills and it’s better to hire a professional in this case.

  • Use chemical solutions: There are certain chemicals that can help clear the problem. This can be used to deal with the bathtub gurgles when the toilet is flushed.

You can use a mixture of water, baking soda, and vinegar use it. To make this solution, you need to boil a lot of water to make sure that there is enough force to remove the clock. Pour the vinegar and baking soda into the toilet to remove the clog. This combination produces a certain reaction that is effective enough to dissolve the clogs.

Once you put the solution pour the hot water into the toilet, starting from the waist level. The hot water makes sure that the clogs are pushed out of the drains.

Allow the mixture to stand until morning to give it enough time to dissolve the clogs and push them down the drain. This method will mostly work on clogs from organic material.

Also, keep in mind to open the windows to allow the airflow in since the chemicals can be quite unbearable.

  • Call a plumber: If you have tested all the above methods and nothing seems to work then you may need to call in a professional plumber.

They will inspect your bathroom and will tell you which part requires fixing or replacing.

Read more posts from indoor category: Ceiling Fan Making Clicking Noise


Above were some of the best fixes on bathtub drain gurgling. However, you should keep in mind that the gurgling drains can be a sign of an even bigger problem with your piping system. That might require a professional plumber to look into the matter.

The smaller problems can be prevented with regular maintenance. If you are not sure how to fix the problem, you can consult a professional plumber to help you out.

Lastly, do not ignore the gurgling noises no matter how faint they are as it is a lot easier to deal with them when formed recently than suffer later with something that cannot be handled easily.

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