How to Prevent Your Toilet From Gurgling When the Washer Drains

If your toilet is gurgling every time your washer finishes a cycle, you’re probably concerned — and rightfully so! Nobody wants to have to clean up the kind of mess a washing machine can make. After all, these appliances use anywhere between 15 to 45 gallons of water per load — just imagine having to mop that up! Essentially, if the machine is causing nearby drains to act up, you’ll want to resolve the underlying issue as soon as possible.

Toilet gurgling when washing machine drains.

Trust me — this isn’t a problem that you’ll want to just cover up by soundproofing the laundry room. In any case, that will only work if you keep your washer in your bathroom since it’s causing the toilet water to bubble. If you want to eliminate the problem forever, you’ll have to deal with whatever is causing the air pressure disparity in your pipes.

Why Some Toilets Gurgle When the Washing Machine Drains

In my experience, there are several reasons your toilet might bubble up when your washing machine drains. Some of them are more worrying than others — and they could even be working in tandem. So let’s go through the most likely culprits.

Both Appliances Use the Same Vent Stack

The first thing you ought to know is that your toilet and your washer are probably connected to the same system of pipes. That’s not always the case. Some buildings have multiple waste lines that are connected to different appliances. However, if you’ve already taken note of the fact that your toilet gurgles whenever the washer drains, they’re definitely using the same system.

That means that they also share the same vent stack. That pipe, which runs up to the roof of the building, maintains the air pressure in the waste drainage system. So if there’s a clog anywhere along the way, it may disrupt the delicate balance of pressure that helps usher waste away.

But gurgling can happen even without a clog. After all, washers typically drain all the water they used for a load of laundry all at once. When that happens, the sheer amount of water in the waste pipes may be enough to upset the air pressure. Consequently, the displaced air could end up floating back up through the water in the P-trap of your toilet or even your sink.

In some cases, the sudden discharge of so much water could create reverse suction, which may pull the water out of your toilet’s P-trap and into the plumbing system. Generally, that happens because of a clog in the vent stack — which is a problem we’ll discuss later on. Suffice it to say that without proper ventilation, washers sometimes end up pulling air from nearby toilets.

Poorly Installed Washer Drain

At this point, you might be wondering why you wouldn’t hear the same kind of gurgling from your toilet when you’re using the sink.

Well, the answer to that question is simple. In comparison to washing machines, sinks send less water down the drain, and they do it gradually. They certainly don’t release enough to create the kind of air displacement you might see when your washer drains.

After all, most washers don’t just slowly drain the used water after finishing a load of laundry. In order to get rid of the water efficiently, they have to expel it under high pressure. However, that might not be possible if the washer drain hose was poorly installed.

As you’ll see in the video, many things could have gone wrong during that installation. For one, you could have neglected to create a P-trap, which would allow the water to be suctioned away from the machine. And even if you did account for the P-trap, the standpipe might be too short or tall to siphon the water into the drainage system.

Furthermore, you’ll need to make sure that the hose is inserted into the drainpipe properly. If you tape it down, the lack of airflow will prevent it from effectively sending water down the drain. And, as we have learned, that will certainly upset the air pressure in the pipes.

Your washer would have to “borrow” the air from your toilet to get the water out, which would naturally create bubbles in the standing water there. Even worse, if the drain hose isn’t properly installed, it may overflow or send water back into the machine.

There’s a Clog in the Waste Pipes

Alright, so we’ve talked about what can happen as a consequence of improper washer drain hose installation. We’ve also discussed why your washer is connected to the toilet in the first place. Now, let’s see what actually causes the gurgling noises that can happen when your washer drains.

A pipe clog is one of the most common issues someone can have with their toilet. If you’ve ever thrown something that you shouldn’t have into the toilet, you may have started the problem that’s haunting you now. Whether it stopped just on the other side of the P-trap or ended up closer to the sewer system, it almost certainly became a clog somewhere down the line.

If you want to avoid even bigger issues, you have to get rid of the clog as soon as you notice it. Waiting for it to simply go away would allow it to get bigger and harder to dislodge with every new flush. In fact, flushing is just as likely to cause a gurgling noise when you have a clog — even without the washer’s help.

Needless to say, if the clog gets any bigger, it might impact the air pressure in the whole system, which can cause washer drainage problems. Trust me — you don’t want to risk flooding the laundry room, especially if you live above someone else.

The Air Vent Is Clogged

As I have mentioned, your washer uses the same waste pipes as your toilet. The vent stack is a crucial part of that system. While the drain pipes take your waste from the drain outlet down into the sewers, the vent stack goes vertically up to the roof. Its main purpose is to maintain the air pressure in the system, allowing you to flush waste without a hitch.

Needless to say, having a clog in the upper part of the system can be just as disruptive as having one that’s closer to the sewers. At first, it wouldn’t prevent your waste from passing through to the sewers. However, the low air pressure in the system would make it almost impossible to efficiently expel waste. That, in turn, could cause clogs in the drain pipes as well.

But since waste never passes through this part of the system, what else could be clogging it? Well, if the vent outlet on the roof is open, it can be a tempting hiding spot for small animals. Birds and squirrels often create cozy nests near the top of the vent stack. Sometimes, they even go too far down to find their way up again.

Aside from animal nests, you could also have leaves and snow clogging the vent. As I have mentioned, these clogs can cause reverse suction or negative pressure. Each time the washer drains, the water creates a seal in the pipes, pushing air to the front and creating a vacuum behind.

How to Prevent Your Toilet From Gurgling When Your Washer Drains

Most of the gurgling noises that occasionally escape your toilet are caused by the air pressure inside the pipe system. Generally, the pressure drops due to a clog somewhere in the plumbing system. But it could also have something to do with improper washer drain hose installation.

So let’s see which of the following solutions you’ll need to implement to prevent the washer water from flowing back.

Fix the Washer Drain Hose

If you’ve noticed that your washer is draining more slowly than it should, you probably have a drain hose problem. Fortunately, that’s something you should be able to fix on your own. You’ll just need to form a P-trap with the hose before connecting it to the vertical standpipe that leads to a drain.

Your machine manual likely has information on how tall the standpipe should be to avoid backflow or overflow. You should also make sure that the hose has plenty of air around it. If you’ve ever used a funnel to fill a bottle, you know why you need to keep it slightly elevated. The airflow eliminates the vacuum that happens if the liquid blocks the entire top of the bottle.

The last thing you need is for the washer water to form a vacuum and pull water from the toilet. After all, the standing water in the P-trap of the toilet is there to prevent noxious fumes from wafting up from the sewer. You really don’t want it moving around!

Push the Clogs Through

On the other hand, if the problem is with the toilet plumbing, just use your trusty plunger. If doing it the normal way doesn’t cut it, try it while keeping other nearby drains closed. That will increase the pressure you’re able to exert on the toilet drain. And if the clog is too deep inside the waste pipes, you could get it through with a drain snake.

As for any potential vent stack clogs, you might have to take a more cautious approach. After all, you’d have to get the clog out from the roof. If you don’t have easy access to it, you shouldn’t even attempt it.

Still, if the vent is easily accessible (and recognizable), you could fish the clog out with a line and hook. If the debris is no more than 48 inches down, you could get it out with a long grabber tool. Alternatively, you could push it through with a blast of water, provided you have a water source and a hose. Then, just cover the vent opening with a mesh material that can withstand all weather conditions.

Happy Day! No More Toilet Gurgling When Your Washer Drains

If you’ve done everything right, you shouldn’t hear any more gurgling when your washer drains. Still, since most of these issues can be recurring, you might want to bookmark this guide for future reference.

And remember, these are only the most common things that could be causing it. If it’s something else — like a problem with the pipes themselves — you may not be able to fix it on your own. In that case, there would be no shame in calling a plumber.


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