Sewer Smell from Toilet, When Flushed, Causes & How to Eliminate

At times, when you flush the toilet, you are hit with a sewer smell instead of a simple washing away of the waste. Odor from your toilet is not only unpleasant but also a health hazard. With the right instructions and tools, you can identify the causes and how to fix the problem.

The causes of a sewer smell from the toilet when you flush include a broken seal at the base of the toilet, a blockage in the drainpipe, a rarely used toilet and a faulty P-trap. Any of or more of these aspects can lead to sewer smells finding their way into the home.

To eliminate the sewer smell, fix the broken seal, unblock the toilet, use a toilet more often or replace the toilet bowl. You might need to enlist the services of a plumber for some of these fixes such as replacing the toilet bowl. With the steps below, you can fix some of the other issues yourself.

Why Toilet Smells like Sewage when Flushed

Some of the reasons your toilet has a sewer smell when you flush it include the following:

You don’t use the toilet frequently enough

This issue is often observed when the toilet is found in the basement, a second home or a room in the house which isn’t used often. What happens in such cases is that the water in the P-trap in the toilet evaporates when it’s not replenished.

The water in the P-trap acts as the seal against sewer gases from the drainpipe. When the level of the water goes down in this pipe, it eliminates the seal allowing sewer gases from the drainpipe into the toilet bowl. That’s what you smell when you flush the toilet.

A broken wax ring

The wax ring of your toilet is located between the toilet seat and the floor and connects it to the toilet’s drainpipe. This wax ring provides a seal that prevents the leakage of water and sewer gases to the outside.

The seal provided by your wax ring can get worn out and thus allow water and gases from the sewer to escape to the outside. You can tell that the wax ring is compromised when you sit on the toilet and it rocks a bit. You may also observe water on the floor around the toilet.

Wax Ring
Wax Ring

A blockage in the toilet

A clog can occur in the toilet due to flushing down the wrong items such as diapers and sanitary pads. This will often hold up wastes making it easy for the foul odors to flow back into the home. This can also be due to poor plumbing where the drain pipes aren’t given enough slope to allow waste flow naturally to the sewer. If wastes stay close to the toilet, their decaying smell can easily find its way into the home when you flush it.

Small drainpipe

A small drainpipe means that wastes find it hard getting into the sewer line. This also means that the toilet can easily get clogged up with gases and wastes being held up rather than flowing freely to the sewer line. This often makes the toilet flush slowly or have bubbles when flushing.

Poor plumbing

Poor plumbing in general can lead to issues with the toilet such as not having the right slope for the drain pipes, not having the right circumference for the pipes and many other issues. One such issue is that gases can be finding their way into the house through leaks in pipes, a poor toilet design and other issues.

Other Causes of the Sewer Gas/Smell from Toilet (when not Flushed)

If you get the sewer gas indoors yet you haven’t even flushed the toilet, possible reasons include:

Cracked toilet Bowl

Although a rarity, the seat of your toilet can easily crack due to either being hit heavily, being dropped or carrying too much weight. Such cracks are dangerous and can also lead to leaks from the toilet. If not taken care of correctly, they can lead to a major disaster where the toilet breaks apart. Trust me, you don’t want to deal with that.

Poor venting

Venting refers to providing an outlet for the sewer gases to flow to the air and to balance the pressure in the pipes with that of the atmosphere. Without a way to vent the toilet, sewer gases build up inside the drain pipe and can easily escape to the house either when flushing the toilet or not.

Symptoms of a clogged vent pipe and how to unclog
Vent Pipe

Some other signs of poor venting of the toilet include bubbling toilets, the toilet taking long to flush and ghost flushing where the toilet flushes itself.

Bad bacteria in the toilet

The drain pipe is filled with lots of bacteria some of which emit awful gases when they break down wastes. When the environment is right, these bacteria can grow into the toilet bowl emerging under the toilet’s P-trap and making the toilet smell badly. This is common in hot and humid areas.

New Toilet Smells like Sewage

A newly installed toilet would smell like sewage because it is not properly installed, it is installed with malfunctioned part(s) or while in installing something broke up.

Incorrect installation and broken parts result in leakage openings that let water and sewer gas escape. You can hire a pro plumber to reinstall your toilet correctly or simply fix the failing parts as discussed below.

New toilet smells like sewage
Newly Installed toilet

How to Eliminate Toilet Sewer Odor

For the issues discussed above, their respective solutions are as follows:

1. Use the toilet more frequently

For the times when the toilet stays for so long that the water in the P-trap evaporates, you will need to use the toilet more often to keep the water in the P-trap replenished. This can be as easy as a flush at least once every week to keep the water fresh and at the right amount.

2. Replace the wax ring

Replacing the wax ring of your toilet requires some work on your end as follows:

  • Turn off the shutoff valve to stop the water from the mains from entering the toilet tank.
  • Flush the toilet then hold the handle down to remove all the water from the toilet tank. If there’s still some water in the toilet tank, open the lid then soak it up with a piece of cloth until the tank is free of water.
  • Use a wrench to remove the bolts holding the toilet to the floor. After loosening the nuts, the bolts will remain while the nuts will come off.
  • Hold the toilet with both hands then gently rock it back and forth while pulling it upwards. It’ll come off the floor and can be removed and placed on a soft base. Make sure you place it on a cushioned floor to prevent damage to the porcelain of the toilet seat.
  • Use a putty knife to gently remove the wax ring from the opening of the drain pipe. You should make sure you have completely removed the wax ring and any debris that may be found on the base of the toilet. Make sure that the slots of of the drain flange are also cleaned properly as you prepare a new wax ring.
  • Position the new wax ring into the opening of the drain pipe with the plastic cone facing downwards and towards the drain.
  • Make sure the T bolts are positioned properly to face upwards as you prepare the toilet seat. In this stage also, you can add any glue, seal or gasket you think will make the seal around the base of the toilet better. You should also take the opportunity to clean the toilet seat with a toilet cleaner or other suitable detergent.
  • Carry the toilet seat and slowly position it on top of the T bolts. Place it down on the opening of the drain pipe gently.
  • Tighten the bolts on the base of the toilet using the wrench then add caulk around the base of the toilet.
  • Turn on the shutoff valve to allow the water into the toilet tank again.

You then test the integrity of the toilet’s wax ring after that.

3.  Unclog the toilet

There are many ways to unclog the toilet. You can use a toilet plunger, toilet auger or wire to push down the blockage. Other times, the toilet simply needs to be flushed with hot water and the blockage will go away.

If the blockage is too deep inside the drainpipe, you may need the input of a plumber to solve it.

4.  Replace the drain pipe

If the drain pipe is too small, it’ll need to be replaced since there is no way around it. These are some of the tasks to leave to a plumber since it involves a lot of dirt and delicate work replacing the drain pipe. Do not attempt it by yourself.

It’s also an opportunity to rectify any other issues with the plumbing system such as giving it the right slope for better drainage.

5. Replace the toilet Bowl

When the toilet bowl is cracked, you will simply need a new one. The procedure for replacing the toilet is similar to that of replacing the toilet wax ring save for the fact that you will be putting back a new toilet seat rather than the old one and won’t be necessarily replacing the wax ring. Make sure the toilet seat you bought is compatible with the fixtures on the floor of your toilet.

6. Properly vent the toilet

Venting the toilet can be done either by adding a venting pipe on the drain pipe or adding a venting device indoors. Venting a toilet can be a daunting task which needs lots of details. While you can easily do the job yourself, we recommend enlisting the services of an expert.

7. Use bleach to clean the toilet

When it comes to killing bacteria in the toilet, household cleaners can do the trick although the addition of bleach to the cleaning process is advised as it makes the whole process more effective.

Clorox Bleach

Tips & Ideas to Prevent the Sewer Smell

To keep the sewer gases out of the house, you need to do the following:

  • Always add caulk to the toilet base after fixing anything under it.
  • Pour hot water into the toilet and the shower drain at least once every week. This helps unclog it and washes dirt away.
  • Flush toilets at least once every week to keep the P-trap filled with water. Since it acts as a seal to the sewer gases, it’ll keep them out.
  • Inspect the drainpipe to check for cracks or cuts which can allow sewer gases out.
  • Checks for clogs in the vents and other parts of the plumbing system.
  • Keep a good cleaning routine for your toilet to prevent the buildup of bacteria.
  • When installing toilets and other household appliances, always adhere to the regulations in your area to prevent issues with poor drainage and gases flowing back into the house.

These are easy tips to add to your household routine yet have tremendous benefits.

Further Reading: Toilet & Bathroom Odor

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