Why Your Bathtub Drain Gurgles When the Toilet is Flushed and How to Fix it

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If you’re wondering why your bathtub drain gurgles when the toilet is flushed, you’re in the right place. There’s nothing more annoying or embarrassing than a gurgling bathtub drain, especially if you have guests over.

If you’re experiencing this awful gurgling sound, don’t panic – it’s more common than you think. The good news is that this issue is easily fixed and you can usually sort it yourself, no plumber required!

With this guide, we aim to show you how to stop your bathtub drain gurgling and the common causes of it. In severe cases, however, you may need a professional plumber and we’ll explain when you should call one a little further down in the guide.

Still have questions about your pesky bathtub drain gurgle? No problem, we’ve put together a useful FAQ section as well! So, if you’d like to know more about irritating bathtub drain gurgles, read on!

Common causes of a bathtub gurgling sound

Before we dive into how to prevent your bathtub drain gurgling sounds, let’s look at some common causes. Being able to identify the root cause of the problem means you’ll be able to repair it more quickly and effectively.

Air is coming in

A bathtub piping system has air vents that control how much air is in the pipes, and sometimes these vents can get clogged up. The valves get blocked by dirt and debris that gets into the piping system.

If the piping system gets clogged the air inside will become trapped, creating a pressure difference. This pressure difference means the air needs to exit through fixture traps.

The problem is, the whole purpose of these traps is so that no air goes through the water but when a vent pipe is clogged, the air will get into the water. This is where the bathtub gurgle comes from.

Air is coming out

Another problem is air coming from the piping systems. If the pipes are clogged with lots of dirt and debris, the pressure difference will start to cause issues, such as a gurgling tub drain!

The pressure in the severely clogged up pipes will build up to force air out through the piping traps. This is a similar problem to the air going in and can be just as destructive.

You don’t have a P-trap installed

Bathtub piping systems typically have P-traps installed. P-traps are specially made to keep the correct amount of water in the pipes as too much water can block the air from entering or exiting the vents.

If your bathtub doesn’t have one, the air can flow through when you flush the toilet and this is why your bathtub drain gurgles when the toilet is flushed. Additionally, when the P-trap is drained you’ll have the same problem with those gurgling noises as the air will flow through the pipes.

The air entering or exiting through the P-trap is the main cause of bathtub drain gurgles when the toilet is flushed, and the noise can be louder if the vents are extremely blocked.

How to fix a bathtub gurgling noise

Now that we’ve explored the common causes of the bathtub gurgles, hopefully, you’ve pinpointed what the problem is. Next, we’ll look at easy ways you can solve the issue quickly and efficiently!

Install a P-trap

If your bathtub doesn’t have one, be sure to install a P-trap. There are numerous reasons to have P-traps installed and all of them are crucial for your health and safety. The most obvious reason for installing one is hygiene and sanitation.

P-traps prevent sewage and wastewater from backing up into the plumbing fixtures. They also prevent harmful gases caused by sewage from re-entering the bathroom through bathtubs and toilet drain pipes. These harmful gases include:

  • Methane
  • Carbon Monoxide
  • Hydrogen Sulfide
  • Nitrogen

All of these gases can be dangerous to your health. Hydrogen Sulfide can trigger asthma attacks and has a characteristic rotten-egg stench.

Methane and Carbon Monoxide can cause headaches, nausea, asphyxiation, and unconsciousness. Unfortunately, many people don’t realize that Nitrogen and Carbon Monoxide can be silent killers because they’re odorless and tasteless.

The water in P-traps stops these poisonous gases from entering your bathroom, protecting you from the harmful effects.

Unblock the bathtub drain with a plunger

One of the oldest but most effective solutions, using a plunger is one of the fastest ways of unblocking drains. It will get rid of anything that’s blocking the pipes and will unclog the toilet and remove any air that’s stuck.

When you use a plunger, be sure to close the bathtub drain first and close all the other sink and shower drains. Use a piece of duct tape to seal the drains so that the air can exit through the vents and not through the drains.

Make sure the bowl of the plunger is totally submerged before you begin. Start plunging for a couple of minutes and then flush the toilet to see if the bathtub gurgles anymore. If the noise is still there, try plunging again as it may take a few attempts.

Unclog the pipes with chemicals

If you don’t want to use a plunger, chemical solutions are a good alternative. Make sure you follow the instructions exactly. Most chemical solutions only need to be poured through the blocked pipes where they will react with the dirt and debris in the pipes.

A good-quality chemical solution will unblock the piping system and let the air exit through the vents. You can also make your own from baking soda, vinegar, and water. However, depending on how bad the blockage is, homemade chemical solutions may not be strong enough.

Investigate the venting system

Checking your venting systems should be a routine procedure, and it should ideally be cleaned even if the bathtub doesn’t make a gurgling noise. Prevention is much better than just solving the issue.

Unblocked and clean vents will let the air flow through them and won’t allow it to pass through any drains.

Remember to also clear the main roof vent as this can get clogged much quicker than other vents. Clear away any leaves, dust, and other debris and use a hose pipe or a high-pressure jet wash to unblock the vents.

Use a plumbing snake to clean a clogged vent

Another solution for your bathtub drain gurgling problem is to use a plumbing snake to clean the vents. This can be a challenging procedure so if you’ve never done it before it’s advisable to call a plumber.

But if you’ve done it before or you feel confident using one then go for it. Sometimes a hose pipe can’t unblock the vents because the blockage is too deep, and this is where a plumbing snake comes in handy.

Insert it into the venting system slowly until you reach the clog. Push the plumbing snake back and forth until the clog starts to loosen or break up. Once you’re sure the clog is broken, run water through the pipe. This flowing water should get rid of the clog.

If the bathtub drain still gurgles when the toilet is flushed, keep repeating the same steps until the drain stops making the gurgling noise.

Install wider pipes

You should also be careful about what you flush down the toilet. Even slightly too much toilet paper can cause a drain gurgling problem, as they can block pipes that are small in diameter.

Therefore, increasing your pipe diameter could reduce blockages and that annoying gurgling noise! The initial cost of installing new pipes may seem expensive, but in the long run, they will save you a lot of money as you’ll have solved the problem completely.

When should I contact a plumber for gurgling drains?

Although the solutions listed above are effective methods of eliminating bathtub drain gurgles, there may be situations where you need to call a plumber.

If you’re trying to clear your roof vents and the blockage is too big, you may have water backing up out of it and you won’t be able to clear it. In this case, it’s a job for a plumber. They’ll most likely have to utilize a sewer auger which is a tricky piece of equipment to use.

Ultimately, if none of the solutions above have worked, it’s time to call a plumber, as it may be an indication of a more serious problem than you first thought. A skilled and qualified plumber will be able to assess the situation and recommend the best plan of action.

It’s also a good idea to contact a plumber if you’re just not confident enough to tackle the problem yourself. If you’re not confident in what you’re doing, a minor gurgling noise could turn into an unnecessarily major problem!

FAQs

Is it bad if my bathtub drain gurgles when toilet is flushed?

Although your bathtub drain shouldn’t gurgle when the toilet is flushed, it’s usually a minor problem that can be easily fixed. However, not resolving the problem quickly can cause it to get worse and turn into a bigger issue, costing you more time and money.

If your drain gurgles when the toilet is flushed, it’s a good idea to contact your neighbors to see if they’re experiencing the same problem. A blockage in a community sewer line could be causing gurgling sounds in your neighbors’ homes too.

If your neighbors are having the same problems, call your sewer authority to report the issue. They can then send someone to examine the sewer main.

How do you fix a gurgling drain?

If your bathtub drain gurgles when the toilet is flushed, don’t worry because it’s typically easy to fix. All of the solutions mentioned above are effective ways of unclogging blocked vents and drains. The plunging method is probably the easiest as most people have a plunger in their homes.

If you’re not keen on using a plunger, using a chemical solution to clear any blockages is a quick and easy way of solving the problem. Alternatively, you can use a plumbing snake, although this does take some precision to reach and clear the blockage.

If you’re not confident in carrying out any of these methods, or none of them have worked, it’s strongly recommended that you call in a plumber. It may be that the problem is more serious than you thought, and it requires a method that only a skilled plumber can do.

How often does a bathroom drain need cleaning?

Cleaning your bathroom drains is one of those jobs that’s really easy to forget. There’s a lot of things that can end up getting into your drains such as food particles, soap, and hair. These can all build up over time and create clogs.

If this is left untreated, it can turn into a serious plumbing issue. But, regular cleaning can help prevent any future problems such as blockages and water backing up. Cleaning your drainage systems monthly should be enough to prevent any serious problems.

A regular monthly clean means you can use safe and effective unblocking methods which will save money, time, and effort!

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