Toilet Smells Like Sewerage When Flushed? (We Have A Fix)

Matthew Mountain
by Matthew Mountain

When you walk into your bathroom one morning and your nose is immediately struck with the unmistakable smell of sewerage, it’s likely you’ll feel disgust, confusion, and worry all at once. It’s almost certain that the sewage smell is due to your home’s connection to the sewer line being exposed, but how could this be?

In this article, the things that cause a bathroom to smell like a sewer will be explained, and solutions to this problem will be put forward as well. In this instance, it’s likely you won’t be able to handle the problem on your own, so contacting a professional plumber will definitely be necessary.

If you’re smelling sewage in your bathroom, it’s most likely because the wax ring that’s under your toilet has been compromised. A compromised wax ring won’t be able to form a proper seal, and water and sewer gas are able to seep through the crack when a proper seal is absent. Other common causes are a cracked toilet, poor ventilation, and drain blockage.

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How a Properly Functioning Toilet Works

Because toilets perform such a vital function, human beings tend to think that these fixtures are complicated. But in reality, the toilet is not a complicated device, and it’s quite likely its simplicity is the reason humans have viewed it as indispensable for hundreds of years.

One thing to keep in mind, however, is that there are a lot of components in a toilet. Therefore, if one of these begins to malfunction, it’s quite likely the system will eventually be rendered inoperable because of this, either for a short time or permanently.

If you want to be able to identify minor toilet-related problems before they make your system unusable, you should know the ins and outs of how a toilet works. This knowledge will avoid a lot of headaches and possibly save you thousands of dollars.

Toilet Operation Step by Step

To flush the toilet, the user must push down on the flush handle that’s located on back-right exterior of the tank. When the handle is pushed, a component known as the flapper lifts up. When this rubber component is lifted, water will exit the tank and enter the bowl. When the handle is pressed, the water and whatever else that’s in the bowl will be sucked down into a drain pipe which leads to the main sewer line.

As the water rushes from the tank to the toilet bowl, the flapper will slowly get back to its default position of resting on the flush valve. Once the flapper is stationary, water will stop entering the bowl and the toilet fill valve, which is sometimes referred to as the ballcock, will begin to bring water back into the toilet tank so the toilet is ready for the next flush.

The sewage smell problem is most likely related to the drain pipe under the toilet, but there are nearby components that, if compromised, could cause a foul smell to manifest in your bathroom.

What Causes the Sewerage Smell?

Unfortunately, the smell of sewage manifesting in the bathroom is not caused by one thing alone. Several malfunctions can cause this undesirable situation to occur, but only the common and most likely causes are discussed in the sections below.

Before you dig into these causes, it’s best to first make this distinction: are you smelling sewage as soon as you enter the bathroom or is this smell only noticeable when the toilet is flushed? Keep your answer to this question in mind as you read about the common causes below, as some are toilet-specific while others relate to the sewer line. Also, bathroom components that are unrelated to the toilet, like the vents, could be causing or accentuating the smell.

The Toilet’s Wax Ring Seal Is Compromised

A compromised wax ring could be the reason why you’re smelling sewage in your bathroom. Every toilet has a wax ring at the base, and this component seals the area where the toilet meets the drain pipe so water and foul odors don’t leak out. If the wax ring is loose or damaged, the sewerage smell will likely be the first indication of this.

One should also know that a minor seal issue may only cause a bad smell to manifest when the toilet flushes, whereas a major crack will allow a prominent stench to linger. And remember that the max ring doesn’t just prevent odors but leakage to. Therefore, if you’re only getting a bad odor and no water leak, then it may be that the crack is so minor that only the sewage odor is escaping.

If you sit on the toilet and it rocks, this is an indication that the wax seal is either significantly worn or broken. The seal can also be damaged if you plunge too hard. Fixing a seal is possible but in most cases replacement is necessary.

You can replace a wax ring DIY if you possess the know-how and tools. Consulting a professional plumber, however, is the option most homeowners pursue, as a professional plumber will ensure the seal replacement goes off without a hitch.

The Toilet Bowl Is Cracked

Cracks tend to occur at the lower part of the toilet bowl, and often they aren’t visible. If your bowl is cracked, then it’s likely you’ll know this by the presence of a water leak. But a cracked bowl can have another unfortunate consequence, with that being sewer gas is able to seep through and linger in the bathroom.

Unlike the wax ring discussed above, a cracked bowl is not an easy fix, and in the majority of cases a cracked bowl is only remedied by getting an entire toilet replacement. It’s best to get this problem fixed immediately, as continuing to use a cracked toilet will only make the situation more costly. Every time you use the compromised system, you cause a water leak and possibly expose yourself to noxious fumes.

There’s Blockage in the Toilet Trap or Drain Pipe

If waste has accumulated in the toilet trap or drain pipe, then a bad smell is likely to be one of the results of this. It could also be that large objects were sent down the drain pipe and now they’re causing a block. If you don’t know there’s a block at the time you do your business, then you add waste to the blocked drain and make a bad situation even worse.

This is also one of the moments when you need to step back and identify whether the foul odor is constant or only noticeable when you flush. Generally speaking, waste blockage will only create a bad smell when one attempts to flush the toilet.

Removing the Blockage

The simplest solution here is to get a plunger—there should be one located near your toilet—and plunge until the block is removed. You could also put a baking soda-vinegar mixture down the toilet to help break up the blockage; doing this in conjunction with proper plunging will clear a block in the vast majority of cases.

If blockage is the issue yet plunging doesn’t work, then you should get a professional plumber to inspect the drain pipe. They’ll be able to remove blockage so long as it exists on your end of the line; anything beyond that is up to the local water company to handle.

They may also identify a problem that’s making blockage more common, and they can remedy this so you don’t have to worry about blockage problems—and bad smells by extension—in the future.

There’s a Clogged Vent

A critical component of the drain pipe is the drain vent, and if this is clogged then you’ll experience a sewer like smell when the toilet is flushed. A properly functioning drain vent releases sewer gas away from the home. But one that’s clogged cannot release the gas properl y and this is why the gas is forced up into the bathroom.

This problem can occur often during the wintertime, especially in places that experience very cold temperatures. This is because frost can close the vent pipe, leaving the sewer gas with nowhere to go. To ensure a clogged drain vent isn’t a problem for your bathroom, you should clean the vents regularly so the air can get through them properly.

Another manifestation of a clogged drain vent is when the backup gas is vented through your tub drain. You’ll know this is happening if you hear a gurgling sound when you flush the toilet. While uncommon, this situation is particularly infamous, as it means your shower—a fixture you use to get clean—has been negatively impacted by a drain vent that can’t properly get rid of noxious sewer gas.

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Final Note

In the end, a sewer-like smell emanating from the toilet is one of the most unpleasant situations that can happen in the bathroom. The good thing is that addressing this problem generally doesn’t involve high costs, headaches, and a lot of energy exertion. In most cases, the problem is caused by a faulty wax ring, meaning the solution is just simple replacement.

But in the situations where your toilet is cracked or you have an unreachable/unbreakable drain clog, it’s best to get help from a professional plumber. After all, they possess the know-how and tools necessary to remedy these situations.

Matthew Mountain
Matthew Mountain

Matt loves everything DIY. He has been learning and practicing different trades since he was a kid, and he's often the first one called when a friend or family member needs a helping hand at home. Matt loves to work with wood and stone, and landscaping is by far his most favorite pastime.

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