Bathtub Drain Gurgles When Toilet Is Flushed

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Piping systems can be complicated for the majority of people, especially if you don’t have any experience with plumbing.

Drain problems can cause a lot of trouble, including messy kitchens and bathrooms, which can cause bad smell in the entire house.

While everyone easily notices when pipes in their home are clogged, different drain problems can occur without you noticing it right away.

Or you might know there’s a problem, but you don’t know which one or how to fix it.

One of the most common problems is the gurgling sound the bathtub or sink make every time you flush the toilet. There are multiple reasons for this, similarly there are many solutions.

In this post, I’ll talk about the most frequent ones and offer a few solutions for fixing the problem yourself.

However, if the problem is more serious and the tips that I’m about to mention can’t fix it, you should consider calling a plumber. Now let’s talk about the most common causes of gurgling drains in your home.

Bathtub Drain Gurgles When Toilet Is Flushed

Why does your bathtub gurgle when you flush the toilet?

This is the question almost everyone asks when they experience this problem.

And while, other than the noise, there aren’t any visible problems, at least at the beginning, this can be very inconvenient. 

Especially when you need to use the toilet during the night, because you can wake up your family members.

This problem can eventually cause an even bigger mess if you don’t resolve it as soon as possible since the reasons that are causing it can clog the drains after some time. Let’s mention the main reasons for this problem.

1. P-Trap

These traps are made strategically in order to keep the right amount of water inside the pipes so it can block the air from exiting since it should exit through the vents.

If your shower or bathtub don’t have these traps, the air will flow through the pipes and create the gurgling noise.

If your drains have the p-trap, then there’s probably a problem with the venting system.

In almost every case, the main reason for this is the air that can be coming in or coming out and going through the p-trap because the vents or the pipes are clogged.


2. Air in

The vents that are placed on the pipes for the right amount of air can get clogged. Also, the main vent on your roof can get clogged from all of the dirt, dust and leaves that end up inside.

This can cause the air to stay trapped and create difference in pressure.

This means that the air has to go through piping traps that are created for the exact opposite purpose.

Their function is to stop the air from going through the liquid. I’m sure you understand the problem now. This is one of the reasons you hear the gurgling noise.

3. Air out 

Another reason could be that the pipes are clogged, and because of that the air is coming out of the drain instead out of the vents that are built for it.

This means that the pressure is being created in front of the object that’s closing them and that the air is creating a difference in pressure once again.

That’s why the air is going through the traps and exiting the bathtub or shower drain when you flush the toilet because that pressure needs to be released somehow.

How to Fix a Gurgling Bathtub Drain

The solutions for these problems are simple, and you should be able to fix them even without any previous experience.

After trying ones I’m about to mention, and still not managing to get rid of the noise, you should call a plumber since he/she will know the exact steps and solutions.

First of all, you should unclog the pipes and clear the venting system. There are a few ways you can make the annoying sound disappear:

1. Use a plunger

This is an old school solution that’s certainly one of the most effective ones. A plunger will help you unclog the toilet and get rid of the objects that are blocking the pipes, as well as the extra air that’s stuck in there.

Make sure to close the shower or bathtub drain, as well as the one in the sink. You should do it with a piece of tape, and you need to be sure that it’s closed tightly so the air can’t go in or out.

Now it’s time to use the plunger in the toilet and use it until the air starts going through the vents again, and not through your drains.

2. Use solutions for unclogging 

If you don’t like using the plunger and you prefer the chemical solutions to unclog your pipes, that’s fine. 

Use them according to the instructions on the bottle and with the unclogged pipes, the air should be able to flow normally and exit the vents.

Pro Tip

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3. Increase the pipe diameter

We all know that we should be careful with things we flush down the toilet. But even when we are, sometimes even a bit of toilet paper can create problems.

This can be fixed with a larger diameter of the pipes which is not very expensive to do and can help a lot in the future.

I’ve increased the diameter of all of the pipes in my home, and I’ve noticed a big difference since I’m having much fewer problems with them after doing this.

how to unclog a tub drain naturally

4. Clear the venting system 

You should consider doing this regularly even when you don’t hear the noise. Prevention is always better and there’ll be fewer chances for problems in the first place.

Clean all of the vents and the air will be able to go through them as it should.

You should also check the main vent that’s on the roof because it could happen that it gets clogged thanks to the dirt, leaves and other things from nature that birds may bring into the vent.

You can try unclogging it with a garden hose and strong water stream, or you can use a plumbing snake.

How to use a plumbing snake

This is a more complicated way of cleaning the venting and pipe system, and I advise you to consult your plumber. If, however, you do have some experience, you could fix the problem by yourself.

This is what you should do, and how you should use a plumbing snake:

Firstly, if you can’t unclog the main vent with the garden hose because the clog is placed deeper in the pipe, you should locate the exact place of the clog.

Once you’ve done that, insert the plumbing snake slowly into the pipe.

If you've found the clog, you should operate the plumbing snake back and forth until you break the clog.

When you think that it is gone, run the water through the pipe and check if the problem is fixed. Repeat this process until you’re happy with the result.

More information: How to Snake a Tub Drain

how to snake a bathtub

On Gurgling Bathtub Drain When Toilet is Flushed

The piping system is one of the most important things in your home, and you should take care of it regularly in order to have a clean and healthy environment to live in.

Clogged drains and vents can cause a lot of problems and create a big mess that’s definitely not hygienic.

That’s why you should solve all of the problems as soon as you notice them. The bathtub that makes gurgling noise when you flush the toilet can be really annoying, but it can also create more trouble later on.

Don’t wait for that to happen and fix the problem as soon as you notice that weird noise.

I hope you find this post helpful and that it makes easier getting rid of that annoying noise and keeping your pipes and vents clean and unclogged.