Sewer Gas Smell In Your House? Here’s What To Do

A pungent sewage smell in your house is not something you can postpone fixing. There is no way you can enjoy the peace and serenity that a home provides while there is a lingering sewer gas smell everywhere.

But what causes a house to smell like sewage? Where does that the smell come from and how can you fix it? I will tell you all about it today.


A sewage smell in the house is mainly caused by a clogged plumbing vent, dry drain traps, clogged drainpipe, leaking toilet wax ring or biofilm/bacteria/grime trapped inside the drains. It could also be caused by a full septic tank backing up through the drains.

A sewage smell in the house that comes and goes is often caused by intermittent factors such as dried-out P-traps or fluctuations in atmospheric conditions that affect the behavior of sewer gases in the plumbing system, resulting in periodic odors.

The following are the causes of sewer gas smell in the house:

1. Clogged Drainpipe

Every fixture in your house has got its own drainpipe. Each of this drainpipe is then connected to the main house drainpipe. The main house drainpipe is the one that empties the waste/sewage to the city’s sewer lines or to the septic tank for those on a sewer system.

If the main house drainpipe is clogged all the fixtures in the house will be affected. You are likely to experience the sewer gas smell in large quantities after flushing the toilet or draining the bathtub.

So, how do you know if the main house drainpipe is clogged?

  • Toilet bubbling/gurgling when flushed – when you flush the toilet, the waste will displace the air in the drainpipe which will be forced to come out through the water at the bottom of the toilet in form of air bubbles.
  • Bathtub/shower drain gurgling after flushing the toilet – If the drainpipe is clogged and you flush the toilet, a vacuum created in the drainpipe will suck air/water from the tub/shower drain and hence the gurgling sound.

A house’s drainpipe can be fully or partially clogged. If it is fully clogged, you need to fix it as soon as possible. After the waste has filled the entire drainpipe, raw sewage will start to back up through your shower/sink drains or even the toilet.

Solution: Unclog the Drain

Before sewage start backing up in your drains, call in a plumber or unclog the drainpipe yourself. It is best if you attempt to unclog the drainpipe yourself before calling in a plumber. Plumbers are not cheap.

If the clog is in your main drainpipe and not a toilet or any of the other drains, a plunger may not be very helpful. What you want to use in this case is a plumber’s snake, also called an auger.

A plumber’s snake is a flexible cable with a hooked head and a cranking handle. Here is how to use it:

  • Push the head down the toilet drain slowly being careful not to scratch the inside of the toilet. Proceed to push it through the toilet trap and down in the drainpipe.
  • If you encounter a restriction pull up the cable slightly and start cranking the handle. Crank the handle clockwise and counterclockwise until you go through the clog.
  • Pull up the cable slowly making sure that its head does not touch the inside of the bowl.

Most toilet augers are only 6 feet long. If you need more length you can buy/rent out a longer motorized auger from a home improvement store.

You could also decide to bring in a professional plumber if you are not confident about using an auger. Plumbers have seen this kind of scenarios plenty of times and will know exactly what to do.

2. Clogged Plumbing Vent


You house drainage is also connected to a vertical pipe known as a plumbing vent or vent stack that runs through the roof of the house. The vent stack helps in circulation of air inside the drainage system by taking out the sewer gases and allowing air inside, to prevent creation of a vacuum.

Dry leaves, small branches and dead rodents are usually the culprits whenever you have a clogged vent stack. During winter it could also be caused by snow.

So, how does a clogged vent stack result in your house smelling like sewage? If the sewer gases cannot flow out through the vent, they will need to look for an alternative exit route.

Most of the time they will come out through the kitchen or bathroom sink or the bathtub/shower drain. And how do you know that you have a clogged vent? The signs looks almost like those of a clogged drainpipe.

  • The toilet gurgles when the bathtub/shower drains.
  • Kitchen/bathroom sink gurgles when the toilet is flushed.
  • Bathtub/shower drain gurgles when the toilet is flushed.

You can also hear all these drains gurgle when draining the washing machine. So why does this happen?

Every fixture in your house with a drain has a piece of pipe fitting called a P-trap. It looks like an inverted P or a U. If you look carefully in your toilet and under you kitchen/bathroom sink you will see it.

Why do these drains need the P-trap? There are 2 reasons:

  1. If something that should not be flushed down the drain ends up being flushed, it is held at the trap preventing it from clogging the drainpipe further down the drainage system.
  2. It at all times hold a little amount of water. This is the water you see at the bottom of the toilet. The water helps to create a barrier, preventing sewer gases from coming up in the house.

In order for all these drains to function properly, there must be air behind the P-trap. If the vent stuck is clogged, air cannot flow freely through the drains.

If say the vent stack is blocked and you happen to flush the toilet or drain the bathtub, a vacuum will be created inside the drainpipe, effectively sucking the water in the sink’s/washing machine’s P-trap.

If the water is sucked inside the drainpipe it means the water barrier has been broken. Sewer gases will therefore flow freely to your houses and hence the sewage smell in the bathroom/kitchen.

Solution: Unclog the Vent Stack

Unclogging a vent stack is actually very easy, assuming you have no fear of heights. Here is how you do it:

  • Grab a ladder and climb to the roof of your house armed with a garden hose and a flashlight.
  • Locate the vent stack. It is usually located straight above the bathroom.
  • If there is a cap on top of it remove it.
  • Check if there is any trash on top of the vent that you can easily remove with your hand.
  • Use the flashlight to see if there is any other visible trash inside the vent. That way you will know how to remove it.
  • Insert the hose inside the vent and start probing the clog with the tip of the hose to see if you can loosen it.
  • If it does not bulge, have someone turn on the water. The water will fill the vent and its weight might be enough to unclog it.
  • If the vent fills with water, it means the clog is quite nasty. You will need to upgrade to a better tool. The plumber’s snake.
  • Feed the snake down the vent until you encounter a restriction. Crank the handle clockwise and counterclockwise until you loosen the clog.
  • Flush the vent with water to make sure that there are no another clogs further below.

3. Dry Drain Traps


As we have seen above, a blocked vent stuck can drain away the water in your drain traps causing sewer gases to start flowing into the house. Blocked vents are however not the only ones responsible for dry drain traps.

If one of your drains has not been used for a long time, the water in the P-trap will evaporate, again breaking the barrier meant to keep away sewer gases from your home.

Solution: Flush the Drains

If you can trace where the sewer gases are coming from (either the shower drain, kitchen/bathroom sink, washing machine drain or even toilet) open the water and let it run for a few seconds. This will refill the P-trap and create the water barrier preventing further discharge of sewer gases.

Every time you come from a trip make it a habit to let water run through all of your drains just in case the water in one of the drain traps had evaporated. Flush the toilet as well. Even if you have not travelled and you have a drain that you haven’t used for a while (basement/guest bathroom) always flush water through it from time to time.

Another reason for dry drain traps is leaks. If a P-trap is leaking, the water inside will after some time be depleted, breaking the barrier created by the water. Sewer gases will then flow out freely to the house.

If you can smell the sewer gases coming out from your bathroom or kitchen sink, duck under the sink and check if there is any water on the floor. If there is, you either have a loose connection or a cracked pipe.

Tighten the loose connections with an adjustable wrench if that is where the leak is coming from. If unfortunately the piece of pipe is cracked you will need to replace it. Just remove it and take it with you to a home improvement store. But similar one and install it yourself. It’s quite easy.

4. Leaking Toilet Wax Ring

A toilet wax ring is a piece of round molded wax that is installed between the bottom of the toilet and the top of the drainpipe. It provides a watertight and airtight seal so that flush water and sewer gases do not leak out.

If the toilet wax ring is not sealing properly, flush water mixed with urine and poop will leak from the base of the toilet and pool around there. A pungent urine/sewer smell will fill your bathroom until you fix the problem.

Apart from leaking flush water at the base of the toilet, sewer gases will also leak out from the base of the toilet and fill your entire house. So how do you know if a bad wax ring is the source of the sewer gas smell in your house?

  • Water pooling around the base of your toilet. If the toilet is caulked to the floor, water may not be visible but you will notice that the basement ceiling will be damp/wet.
  • A wobbly/rocking toilet.
  • Bad odor coming from around the toilet.

It is however not always the case that when you have water pooling around the base of a toilet you have a bad wax ring. Sometimes the toilet may have a hairline crack draining away the water to the floor. In this case, the toilet will need to be replaced.

Solution: Replace The Toilet Wax Ring

Replacing a toilet wax ring sounds like a really tough task but it is actually quite easy. Plumbers however charge a lot to do it. It will only take you longer if your toilet is caulked to the floor.

Before replacing a toilet wax ring, make sure that your toilet is not leaking because of loose toilet bolts. Rock the toilet a bit to see if it is wobbling.

If you have a wobbly toilet, grab an adjustable wrench and tighten the 2 bolts on each side of the bowl. Sometimes the bolts are covered with plastic caps. Pry them off with a screw driver.

After tightening the toilet bolts mop the base of the toilet and flush the toilet a couple of times. Check out for leaks.

If you have leaks or if the toilet is not wobbling in the first place, proceed to replace the wax ring

How to Replace a Toilet Wax Ring

  • Turn off the water to the toilet. The shut off valve is on the wall behind the toilet. Turn it clockwise or the way.
  • Flush the toilet and hold the lever down to remove as much water as possible.
  • Remove the tank lid and mop the inside of the tank dry with a sponge.
  • Wear rubber gloves and also soak up the water at the bottom of the bowl.
  • Disconnect the water supply line from underneath the toilet tank. Do not use a wrench unless the coupling is too tight.
  • If your toilet is caulked, cut through the caulk with a sharp knife.
  • Loosen the 2 toilet anchor bolts with a wrench.
  • Grab the toilet with both hands and rock it about to completely break the wax seal.
  • Lift it off and gently lay it on its side on top of a rag/towel.
  • Plug off the drainpipe with a rag to prevent more sewer gases from coming up inside your house.
  • Use a putty knife to scrap off old wax from the toilet outlet and also on top of the closet flange. The closet/toilet flange is the circular pipe fitting that connects the toilet to the drainpipe.
  • Check the condition of the anchor bolts. If they are corroded then it would be a good time to replace them as well.
  • Set up a new wax ring on top of the closet flange. Wax rings cannot be reused.
  • Remove the rag from the drainpipe.
  • Lift the toilet and bring it just above the wax ring. If you can get someone to help you align the anchor bolts with the 2 toilet holes then let them do it. Set the toilet nicely on the wax ring.
  • Grab the toilet on both sides of the bowl and push it down gently to compress the wax ring.
  • Slide a washer and nut on each bolt and tighten them alternatingly. We tighten the bolts alternatingly to keep the toilet level.
  • Connect the water supply line back to the toilet.
  • Turn on the water shut off valve and let the tank fill.
  • Flush the toilet a couple of times and check for leaks at the base of the toilet. If none then your problem id fixed.

Note: If you have a two-piece toilet, you might want to remove the tank separate from the bowl to minimize the risk of it cracking. Read more about that here.

5. Full Septic Tank


If you are on a septic system, the reason for that foul sewer gas smell in your house could be because the septic tank is full or just about to be. Once the septic tank is full, waste start accumulating in the drainpipe.

When you drain one of the fixtures in your house, the waste displaces the sewer gases in the drainpipe which is then forced out through one of your other drains in form of bubbles.

The other telltale signs that your septic tank is full are:

  • Your fixtures are draining slowly
  • Water pooling in your lawns
  • Greener lawns than usual

If this is the case, you will need to empty you septic tank as soon as possible. Waste from your house will fill up the drainpipe pretty fast and when the waste has nowhere else to go it will start backing up through your drains. It is not pretty!

6. Biofilm/Bacteria/Grime


We use a lot of products in our shower/bathtub, kitchen sink, bathroom sink and washing machine. While most of these products wash away down the drain, some are left trapped inside the P-trap and the vertical pipe.

The accumulated mess inside the trap is called a biofilm. This is because most of these substances are organic. And what do we know about organic waste? It decomposes releasing an unpleasant sewage smell.

If you can trace this smell especially in your bathtub/shower drain or kitchen sink, fixing it is really easy. Proceed as follows:

  • Pour 1 gallon of hot water down the drain. The hot water will dissolve the soap scum and other debris as well as wash down most of the trash inside the trap and drainpipe.
  • If you are working on the bathtub, remove the drain stopper. This will depend on the type of stopper you have in your bathtub.
  • Pour half a cup of baking soda carefully down the drain.
  • Now slowly pour 1 cup of vinegar down the drain as well. Remember vinegar really quick with baking soda hence the need to pour the vinegar slowly.
  • Give the solution 30 minutes to work out its magic. The solution will eat way the biofilm breaking it down into smaller pieces.
  • After the 30 minutes, blast hot water down the drain. This will now wash down all the broken down waste leaving you drain trap and drainpipe clean and fully open.

You will also notice that your kitchen/bathroom sink has an overflow opening at the top. That is a perfect place for grime/grease to collect whereby it will start producing an awful stench after a while.

This is however a problem affecting kitchen sinks more than bathroom sinks. Here is how to fix it:

  • Grab a funnel and insert its outlet inside the sink overflow.
  • Pour about half a cup baking soda down the overflow through the funnel.
  • Slowly add about half a cup vinegar down the funnel as well.
  • Wait for thirty minutes.
  • Insert the funnel gain in the overflow and blast hot water down the overflow to wash down everything trapped inside.

And that is how to get rid of sewer gas in the house.


A sewer gas smell in a house is an unpleasant odor caused by the presence of gases typically found in sewage and wastewater systems. These gases, including hydrogen sulfide, methane, and ammonia, can enter a home through drains, pipes, or plumbing fixtures when there is a problem with the sewer system or plumbing infrastructure.

Common reasons for sewer gas odors in a house include blocked or damaged sewer lines, dried-out P-traps in drains, or improperly vented plumbing systems. Detecting and addressing sewer gas smells is essential as they can be harmful to health and indicate potential plumbing issues that may require professional intervention to ensure the safety and comfort of the home’s occupants.

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