Toilet Smells Like Sewage When Flushed — Here’s Why!

Isn’t it awkward when your toilet looks neat and clean but still generates that disgusting sewer odor? It’s not unusual to see something like that, but it doesn’t make the scene less annoying.

If your toilet smells like sewage when flushed, it is probably because of the damaged wax ring. If not, the problem lies in a cracked toilet bowl, clogs in the drains, or bacteria buildup.

The only remaining cause is unlikely — the water from the bowl evaporated because you weren’t using the toilet for a long time.

Problems are versatile, but the only thing that matters is that you can fix them all single-handedly. Let’s see how!

Problem 1: Bacteria Buildup Under the Rim

Rim jets are below the bowl rim, which makes them invisible. These holes enable flushing, keeping the toilet clean with strong water jets. But jet holes often accumulate dirt over time, so they clog fully or partially.

Bacteria buildup under the rim, so it soon starts emitting stinky sewer gas. Although you can’t see the stinky source from above, it’s there, and it’s making your bathroom experiences much worse.

Solution: Clean the Rim Jets

You don’t need special tools to clean the toilet bowl rim jets. Removing bacteria buildups is easy — use the toilet brush to scrub out waste deposits from all holes and jets under the rim.

If the clogs are too stiff, use a wire brush to thoroughly clean the holes. A metal coat hanger will do well — bend it to get a sharp wire, so you can breach the hard waste deposits in the rim holes.

After that, you can take a sponge and your favorite cleaning product to wipe the toilet rim. When you complete all these steps, your toilet will flush as usual —and it won’t smell again.

Problem 2: Cracked Toilet Bowl

A cracked bowl will surely smell bad because it lets sewer gas enter your bathroom. Cracks are often small and barely visible, so you probably don’t feel the sewage smell too strongly and frequently.

Cracks in bowls are very common — the reason may include mechanical impact, harsh cleaning chemicals like Drano, or frequent temperature fluctuations. Repairing a damaged bowl is impossible, so you’ll need to replace it with a new model.

Our suggestion is to install a highly durable toilet bowl that guarantees long-term efficiency. You should also pay attention to water consumption — some bowls need more water than others to flush properly. 

That’s why a dual flush mechanism is the finest system for homeowners who care about nature and their utility bills.  

Full-flushing American Standard H2Option uses 1.6 gallons of water, but its conserving flush spends only a gallon. This makes the bowl ideal for both types of homeowners — those who want strong flushing and those who protect nature.

Solution: Replace the Cracked Bowl

Replacing your toilet bowl may turn into a dirty DIY project, so prepare tools such as towels, buckets, and rubber gloves. Besides that, you should get a pair of pliers, an adjustable wrench, and screwdrivers.

Now you can start by closing the shutoff valve. It’s a small knob behind the toilet that allows or prevents water from going to the toilet tank. You must turn it clockwise — if the shutoff valve won’t shut off, it’s probably too old and rusty.

In that case, use WD-40 to spray the knob. Leave it to work for 15 minutes, and you’ll twist the valve easily afterward. The water supply is off, which means you can empty the entire toilet by pressing the flush handle.

Detaching the metal supply hose that brings fresh water into the tank is the next step. The hose has a threaded nut connecting it to the toilet tank, so you’ll need to unscrew it. When you do it, you can also unscrew tank bolts and remove the tank.

The next task is to grab the wrench and twist the base bolts counterclockwise — it will loosen the bowl and allow you to remove it.

Before installing a new bowl, inspect the toilet flange. It’s a plastic entrance to the outlet drain, so you don’t want to leave it broken or malfunctioning. An uneven flange can cause water leakages and increase the risk of sewer smells.

Finally, you can install a new toilet bowl. Place it on top of the flange and its wax seal — it should fit tightly to the ground. After that, you can reinstall the entire toilet:

  • Screw the base bolts by turning them clockwise
  • Put back the tank and screw its bolts with the wrench
  • Attach the metal supply hose
  • Open the shutoff valve to enable water supply

Problem 3: Damaged Wax Ring

When you inspect the toilet flange, you will also notice a wax seal on top of it. It’s a wax seal that’s flexible enough to stay between the flange and the bowl, supporting the latter to make it stable.

A damaged wax ring makes the toilet wobbly and allows smelly sewer gas to go back to the bathroom. You’ll know that the ring is broken by water puddles — the toilet is leaking at its base.

Solution: Replace the Wax Ring

Replacing the damaged wax ring requires time and precision because it’s a part that prevents toilet leaks. It hides under the toilet bowl, which means you should count on dirty work and elbow grease.

  • Close the water supply by turning the shutoff valve clockwise
  • Detach the metal supply hosepipe with the adjustable wrench
  • Flush the toilet to empty the tank
  • Unscrew tank bolts and remove the entire part after that
  • Unscrew the base bolts using pliers or your wrench
  • Disconnect the toilet bowl from its floor base

When you remove the toilet bowl, place it on the side — put a towel on the floor to protect it from cracks. The bottom of the bowl will contain the remnants of the old wax ring, so take a putty knife and use it to remove them.

Do the same with the toilet flange — remove the wax seal to create room for a new model. Clean the entire area to set the stage for the new wax ring.

When you do that, apply a new wax ring on the flange before reinstalling the toilet bowl. There should be no space between the ring and the bowl, so press the porcelain item firmly against the ground to attach it.

Now you can reassemble the toilet like this:

  • Tighten the toilet base bolts to secure the bowl
  • Put back the toilet tank and screw its pair of bolts
  • Attach the supply hosepipe to the tank
  • Open the water supply valve by twisting it counterclockwise

We recommend flushing the toilet to ensure everything is fine — there should be no leaks, and your toilet shouldn’t wobble with a new wax seal.

Problem 4: Clogged Vent

The air vent is a pressure regulator. It’s a vent pipe that transfers fresh air to the drain pipe, so the pressure can restore after flushing to prevent a stinky toilet.

The problem occurs when the air vent clogs — there is no air to enter the vent pipes, so the flush system goes out of balance. A clogged vent results in a drainage vacuum, preventing a small amount of water from returning to the bowl.

If there is no small puddle in the bowl, nothing stops sewer gas from returning and causing a foul odor in your bathroom. That’s why your toilet smells like sewage when flushed.

Solution: Unclog the Air Vent

The downside of this problem — apart from a smelly toilet — is that you must climb on the roof. That’s where the vent pipe is, so you’ll need to go up to unclog it.

First of all, open the vent pipe’s entrance because it’s probably full of fallen leaves. It allows you to approach the pipe and insert a garden hose — pouring water down the line should eliminate debris.

However, the waste is sometimes too hard to disappear like that. In such circumstances, you’ll need a toilet auger. It’s a flexible rod that you can use to break even the most stubborn clogs inside the vent pipe.

After drilling through the clogs, you can again pour water to clean the entire air supply line. It will restore the system to normal and stop disgusting bathroom smells.

Problem 5: Clogged Toilet

Toilet clogs can cause foul odor because they prevent the toilet from handling poop and urine smells. If the clog is too big, it will create waste buildups somewhere in the toilet drain.

Solution: Unclog the Toilet

Don’t call a professional plumber to unclog the toilet. Use a cleaning tool instead — a toilet auger will do just fine! Here’s how the auger works:

  • Insert the auger down the outlet drain line
  • Rotate its rubber handle to push the drill deep down
  • Keep rotating until you reach the clog
  • The tool will stop when it touches the blockage, so remember to give it the extra push
  • The toilet snake drills through the clog until it breaks apart

Now your toilet is free again, so it can dispose of waste and stop the lousy sewer gas smell.

Problem 6: Water Evaporation

The last problem is the least common, but it happens if you travel frequently or don’t visit your cottage too often. In this case, the water in the bowl may evaporate because you don’t use the toilet for a long time.

Solution: Clean the Toilet and Ventilate the Bathroom

The solution is fairly simple — flush the toilet to fill the bowl with water. The water will refresh the entire plumbing line, while some of it will stay in the bowl to protect your bathroom from awkward smells.

After that, you can clean the toilet to make sure there’s no residual waste in it.

The Bottom Line

Discovering bad sewer odors in the bathroom is annoying, but you can probably solve the problem soon. Begin by identifying the cause — it can be one of these things:

  • A clogged toilet or air vent
  • Bacteria buildup under the rim
  • A broken wax seal or bowl
  • Water evaporation

If you don’t want to call a licensed plumber, follow the steps we discussed above — they will help you solve each of these smelly toilet issues!

FAQ

Is it dangerous when your toilet smells like sewage?

No, it’s almost never dangerous when the toilet has a sewage smell. It feels bad, but that rotten eggs smell can hardly hurt you. However, it indicates a problem with the plumbing system that you have to pinpoint and resolve.

Can sewer gases come up through the toilet?

Yes, sewage gases can come up through the toilet when there is no water in the bowl. A small puddle in the bowl stops the gases from going to the bathroom, so the smell may appear if the puddle is not there.

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