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Toilet Bubbles & Gurgles When Washer Drains [FIXED]

Are you dealing with a bothersome bubbling or gurgling in your toilet whenever the washing machine drains? While this is fairly common in many households, you’re right to be concerned. Any gurgling noise coming from the toilet is not a good sign.

Often, this is a consequence of suction or negative air pressure somewhere in the drain system, the vent stack, or even both.

Depending on the severity of the gurgling sound coming from your toilet, or even from showers, tubs, and sinks, for that matter, you can typically troubleshoot this annoying noise on your own. But first, get to the bottom of it to find out what is exactly causing your toilet to bubble when the washing machine drains.

bathroom washing machine

Why Does the Toilet Bubbles When Washer Drains?

The reason why the toilet bubbles when you drain the washing machine is that air pushes its way through the water. This happens when something is blocking the pipes or vents, causing negative pressure, which is why your toilet makes that bubbling sound.

There are several reasons why there is air in the pipes:

1. Your Toilet Has Connecting Drains 

A common source of the gurgling sound and bubbles in your toilet whenever the washing machine drains is because your washer drain or washing sink is connected to the toilet waste line. This plumbing configuration isn’t uncommon, and thus many homeowners have to deal with that annoying bubbling sound from the toilet.

For example, the washing machine and its drain might be placed between the toilet and the soil stack. This means the washer drain is connected to the toilet drain, and any negative air pressure when you drain the washing machine can create bubbles in the toilet. It is prevalent when the drainpipe between the toilet and the washer is considerably short.

2. Toilet and Washer Are Connected in One Vent Stack

The plumbing configuration in your bathroom may be that the toilet and washer are connected in a single vertical stack. This means the fixture and your toilet share a common vent or wet vent, as plumbers call it.

It’s another common reason why air pressure finds its way into your toilet, causing a gurgling sound whenever the washer drains.

3. There’s a Partial Clog in the Main Drain/Waste Pipe

Besides problems in your drain hose installation, another possible reason for your toilet bubbling is when the washer drains are clogged in the waste pipes.

Most often, such problems are caused by pipe clogs. Someone might have thrown something into the toilet that they shouldn’t have. Tissues, for example, or sanitary pads could stop just around the P-trap of your toilet or end up clogging the pipe near the sewer system. Either way, you’re going to deal with the consequences of a clog somewhere down the line, like a bubbling toilet when you drain the washing machine.

4. You Have A Clogged or Blocked Vent Pipe

The vent stack is a crucial part of your toilet and washer’s drain pipe. It maintains air pressure in the system so you can flush or drain waste without any issues.

Needless to say, whether there is a full or just a partial block in the vent pipe, negative air pressure can develop in the drainpipe. When this happens, that air will pull from wherever is possible, including the water in your toilet. This is because water forms an incredibly airtight seal inside the pipe.

Negative air pressure anywhere in the pipe creates a vacuum. Hence, bubbles may form in the toilet when you drain the water in the washing machine.

So, what can be blocking the air pressure in your vent pipe? It might be a small animal like a bird or a squirrel who found its way through an open vent pipe. Other times, fallen leaves or snow can clog your vent stack.

5. Faulty or Poorly Installed Washer Drain

The washing machine drains water more quickly than, for instance, the sink. This means your washer pumps water at a higher pressure, which can cause bubbling. But another common culprit is a faulty washer drain.

Homeowners often add washer drains as an afterthought, which means drains are connected to the nearest waste pipe. More often than not, households neglect to provide a P-trap, causing a water suction away from the washer when it drains. Another issue could be using a standpipe for the washer drain that is too short or tall.

Without proper air pressure in the pipe to help drain the wastewater, the washing machine would likely “borrow” air from the toilet to help push the water out into the sewer. Hence, it creates bubbles in the standing water in the toilet.

Any gurgling happening because of an improperly installed washer drain can lead to more problems later on. For instance, the water may overflow or send the wastewater back into the washing machine.

How to Prevent Your Toilet From Gurgling When the Washer Drains

Check out the following solutions to help prevent any bubbling in the toilet when the washer drains. The solution you need to implement will depend on what’s causing the issue in the first place.

Plunge the Toilet

If the reason for your toilet bubbling when the washer drains is the drainpipe, plunging the toilet is one of the easiest fixes. It works for partial or moderate clogs.

But before you start plunging the toilet, ensure that you have sealed off the drains first. Duct tape works well for that, and don’t forget to put the stoppers in the sink as the bathtub drains. Otherwise, you might have to deal with a bigger mess than you signed up for.

Deal with Deeper Clogs

If plunging the toilet full of water ten to fifteen times doesn’t work, then you’re probably dealing with a stubborn clog. You’ll need to go deeper and remove the clog another way, using an air bladder or a plumber snake. You can purchase either of these cheaply from any hardware store.

Follow the instructions on the package and either solution should force clogs to drain into the larger pipe, opening the water flow.

Clear the Vent Stack

If the bubbling toilet problem continues despite completing the above steps, you may be dealing with a clog in the vent stack. You need to go to the roof and check whether anything is blocking the vent.

Once you’re on the roof with a flashlight, look for clogs inside the pipe, such as leaves, debris, small animals, and even birds nests. Then, remove any debris that could be blocking the airflow. After you’re done, replace any vent pipe covers that have been damaged so that debris and small animals can’t enter.

Fix the Drain Hose

Lastly, if the toilet bubbling problem stems from your washing machine’s drain, it’s time to fix it. You’ll know that is the problem when your washing drains slower than it should.

To fix this problem, install a P-trap in your washer drain before connecting it to the standpipe that leads to the drain.

Kyle Tucker

Kyle from Kyle Tucker Plumbing is a certified plumber with over 20 years of professional experience installing plumbing fixtures such as bathtubs, sinks, and toilets, as well as installing gas lines and water pipes, performing bathroom repairs, and more.

Kyle knows how to deal with every plumbing issue that modern homeowners encounter, and he shares his lifelong experience with readers in an engaging and easy-to-digest way.

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