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Why Your Toilet Stinks When Flushed: How To Fix It

Why Your Toilet Stinks When Flushed: How To Fix It

Your toilet stinks when you flush it, and you are not sure why. This is not a rare problem to have with a toilet—but it’s not pleasant, either. So what’s behind the smell?

There is a multitude of potential causes of a toilet stinking after it is flushed:

  1. The toilet wax ring is not sealed
  2. Clogged toilet drain
  3. Bacteria from sewage
  4. A clogged plumbing vent pipe
  5. The water in the p-trap has evaporated
  6. Rotted or cracked drainpipes
  7. A missing cleanout plug
  8. A cracked toilet bowl
  9. The toilet doesn’t get enough use

Tips on how to resolve all these issues are included in the article below. Fortunately, most of these problems can be fixed as a simple, low-budget DIY project.

Reasons Why Your Toilet Stinks When You Flush It

Before you can get rid of the bad toilet smell for good, you’ll first have to figure out what is causing the odor to begin with.

There several root causes of a toilet being on the fritz:

1.   Toilet Wax Ring Is Not Sealed

The toilet wax ring acts as a seal between the toilet and the toilet anchor flange, keeping the toilet attached to the drain and bathroom floor. A properly sealed wax ring acts as a mold-resistant and bacteria-resistant anchor for the toilet.

The wax ring at the base of your toilet is pretty much what it sounds like: a ring of sticky wax that forms a watertight seal between the toilet base and the sewer pipe. Wax rings generally require little to no maintenance and will often last the lifetime of the toilet itself.

However, there is a chance that the wax ring on your toilet was either not installed properly or has dried out and crumbled prematurely.

Signs that your toilet wax ring may no longer be sealed include:

  • A lingering foul odor around the toilet
  • Water leaking out from the base of your toilet
  • A toilet feeling unusually wobbly

2.   Clogged Toilet Drain

A toilet drain clogged with debris is another potential root cause of foul odor after flushing. Even a small clog in the pipe that is unnoticeable may lead to a foul odor after flushing.

Signs, other than overflowing, that your toilet drain may be clogged include:

  • The water may start flushing abnormally and may stay in the bowl longer.
  • The toilet doesn’t flush at all.
  • The drain is emitting a foul odor.
  • The water in your toilet, shower, or bathtub is gurgling or making a bubbling sound. (This means that there is air trapped somewhere in your pipes or there is water backed up somewhere in the sewer lines.)

3.   Bacteria From Sewage

Hot and humid conditions during the summer months allow microorganisms such as bacteria from sewage to thrive. It is possible that microorganisms from the sewer have made it to your toilet via some kind of blockage in the sewer lines or weather conditions.

Sewage back-ups can occur after events of blockage in the sewer lines or heavy rainfall events in communities that combine sewage and storm water outflow. Proper remediation after a sewage back-up event can help prevent foul odors from remaining in the home.

4.   Plumbing Vent Pipe Is Clogged

One of the more common causes of a foul odor during flushing is a clogged plumbing vent pipe.

Plumbing vent pipes are responsible for allowing air into a home’s plumbing system. The vent pipes balance the pressure in the pipe as water traverses the drain.

Plumbing vent pipes also vent off sewage gases. As long as the vent pipes remain unblocked, there will be a steady air supply available to counteract either negative or positive pressure that develops when a toilet is flushed.

Signs of a clogged plumbing vent pipe include:

  • The toilet gurgles after it has been flushed
  • The toilet bowl drains more slowly than normal
  • You notice a foul odor after flushing the toilet

5.   The Water in the P-Trap Has Evaporated

This is one of the most common causes of sewer odors within a home. Each drainage system, including those connected to the shower, floor, and plumbing fixtures, has a P-trap. These traps are required by building codes. The P-traps are made of U-shaped pipe/tubing connecting a floor drain or plumbing fixture to the line going to the sewer or septic tank.

The P-trap holds a small amount of wastewater within the pipe to prevent sewage odors from escaping to the house. Signs that the water in a P-trap has been evaporated include a foul odor that you cannot pinpoint directly to your toilet.

6.   Rotted Or Cracked Drainpipes

The cause of a foul odor after flushing may be more serious than some of the other potential causes discussed so far. The root cause of the foul odor may be a rotted or cracked drainpipe within your plumbing system. Signs that your sewer line may be in dire need of repair include:

  • An odor of sewage in your home
  • You notice mold growing on your walls or ceilings
  • Frequent sewage back-ups or blockages
  • The drains are slower than usual
  • DIY fixes such as unclogging drains or vent pipes don’t seem to be working

7.   A Missing Cleanout Plug

The source of the sewage odor may be a missing cleanout plug rather than an issue with your toilet. Cleanout plugs are located underneath floor drains. A missing cleanout plug can cause sewage gas to escape into your home in much the same way that an issue with your toilet would.

8.   A Cracked Toilet Bowl

After flushing, the foul odor in your bathroom could be due to a cracked toilet bowl, which can be a major issue. Usually, a cracked toilet bowl is accompanied by a leak, but this may not be immediately apparent.

Plumbing experts note that cracks will often occur at the bottom of the toilet bowl, where they cannot be spotted easily.

9.   You May Not Be Flushing Your Toilet Enough

It is also possible that your toilet smells every time you flush it because you do not use it enough. This is possibly the case if you have an extra toilet in a basement where it is not often used.

When toilets are not used very often, the water in the toilet bowl can evaporate. The water in the toilet bowl helps keep sewage odors from escaping the drainpipes beneath the toilet.

To prevent this water from evaporating and sewage gases from entering the bathroom, it is recommended that you flush each toilet at least once a week. This will help keep the toilet bowl filled with water consistently, trapping odors found in drainpipes beneath toilets.

How to Stop Your Toilet From Stinking When Flushing It

In this section, you will find tips on how to go about fixing each of the problems noted above for contributing to a foul odor in your bathroom after you flush your toilet. If any of these issues appear to be beyond DIY repair, it is encouraged that you connect with a qualified local plumber.

Sealing the Wax Ring

If you happen to notice water leaking from the toilet base, it is recommended that you make sure you fully inspect the water damage before starting the project.

Leaking water can damage a subfloor to the extent of weakening the mounting bolts attaching the toilet to its anchor flange. You may need to even cut away some of the subfloor and replace it.

Detailed instructions on how to replace the wax ring under your toilet can be found here.

Removing the Toilet

  1. Your first step will involve shutting off the water supply by turning the knob located next to the toilet. Use a plunger to force any remaining water down the drain before removing the toilet.
  2. Place a bucket underneath the water supply line by the valve.
  3. Disconnect the water supply line from the toilet.
  4. Loosen and then remove the nuts keeping the toilet attached to the floor.
  5. The bolts may be corroded. If they are corroded, apply penetrating oil, such as this spray, to the bolts first.
  6. Make sure to avoid applying too much pressure to the bolts to avoid damaging the anchor flange.

Installing a New Wax Ring

You do not need many tools and materials for installing a new wax ring underneath your toilet. You will primarily need a new wax ring such as this. You will also need disposable gloves, a plastic putty knife, and mineral spirits.

  1. Put on a pair of disposable gloves to avoid getting your hands sticky and grimy from the wax.
  2. Make sure that you are providing plenty of ventilation.
  3. Remove and discard the old wax ring.
  4. Use a plastic putty knife and a rag soaked in mineral spirits to help remove the remaining wax.
  5. Plug the drain with a ball of old rags large enough to not fall into the drain. The purpose of this plug is to prevent sewer gases from entering your home.
  6. Remove old bolts from the toilet anchor flange and check the flange for any damage or missing pieces.
  7. While still wearing the disposable gloves, install the new wax ring.
  8. Then you will re-install the toilet using the steps shown here.

Unclogging the Toilet Drain

Some blockage may cause a foul odor present after flushing within the toilet drain. There are several different methods for unclogging a toilet drain.

The conventional method of using a plunger will often work fine, but you may need to explore other options.

Use a Toilet Plunger

Using a toilet plunger such as this one is a quick and easy way to see if you can unclog a toilet drain. When you use the plunger, quickly push down on the handle 2 or 3 times, as is recommended by this plumbing company. After hearing the water travel down the drain, flush the toilet to confirm that it has been unclogged.

Chemical Drain Cleaners

Chemical drain cleaners only help jar loose biological debris, but they can be useful if you use them properly. 

Be sure to take care when using chemical drain cleaners. If used improperly, chemical drain cleaners can lead to more damage than what you started with.

 Look for chemical drain cleaners specificity designed to unclog toilet drains such as:

Homemade Drain Cleaners

You can also be creative and enlist the help of homemade drain cleaners. Though less potent than store-bought chemical drain cleaners, homemade drain cleaners can still be effective.

Homemade drain cleaners that people swear by include:

  • Baking Soda and Vinegar: Not only are these solutions good deodorizers, but they can also help unclog a drain.
    • First, add one cup of baking soda to the toilet.
    • Then wait a couple of minutes and slowly add a couple of cups of vinegar to the mix.
    • Wait for a few minutes and then check to see the mixture is doing the trick by flushing the toilet.
  • Dish Soap and Hot Water: Shampoo and hot water may work in the same capacity as dish soap and hot water.
    • First, heat up a gallon of water on the stove.
    • Squirt some dish soap or shampoo into the toilet bowl while you are waiting for the water to heat up.
    • Pour hot water (but not boiling) into the bowl and wait for the mixture to soften the clog.

Plumbing Snake

You may be able to rent a plumbing snake from your local hardware store to help unclog your toilet drain. Make sure that the equipment is for use with toilets first.

A plumbing snake is an auger-like tool that spins around and dislodges debris within the drain. You can learn more about plumbing snakes here.

Get Rid Of Odor from Sewage Bacteria

It’s possible that the foul odor after flushing could be traced to bacteria from sewage. The heat and humidity of summertime contribute to ideal conditions for bacteria and microorganisms often found in sewage. Bacteria can take hold along the rim of the toilet bowl and then multiply in number.

You can get rid of bacteria in your toilet bowl by pouring a few cups of bleach into the overflow pipe or flush valve located inside the toilet tank. You can also use vinegar to clean and deodorize your toilet bowl.

  • First, squirt vinegar around the entire perimeter of the toilet bowl above the waterline.
  • Then pour ⅔ of a cup of vinegar into the toilet bowl.
  • Let the vinegar do its magic for at least 15 minutes before flushing.
  • If you notice a visible ring from the waterline, swish a toilet brush at and above the waterline before flushing.

Unclogging a Plumbing Vent Pipe

The plumbing vent pipe is the component of your plumbing system responsible for venting off-gases and adding air to the pipes to balance out negative and positive pressure in the system.

According to this article, you may have to go to your roof to take care of an issue related to your plumbing vent pipe. The vent openings are located on top of the roof.

If the plumbing vent gets obstructed somehow, then air might not be able to get into the drain, and the vacuum can pull water out of P-traps. This can allow sewer gases to enter the home.

 To clear the blockage from a plumbing vent pipe:

  1. Pull together a screwdriver and a garden hose with an adjustable nozzle to clear the blockage. The purpose of the screwdriver is to unscrew the cap on top of the plumbing vent.
  2. Start by setting up a ladder to get up to the roof.
  3. Inspect the plumbing vent for leaves or other debris that might be causing the blockage.
  4. Take the garden hose with the adjustable nozzle and spray water directly into the vent.
  5. The stream of water will generally dislodge most obstructions.
  6. If the obstruction doesn’t budge, you will likely need to enlist the help of a plumbing snake or auger.

Restore Water in P-Traps

There are several possible reasons that a plumbing trap could lose water:

  • Overly dry air conditions can cause the water in the trap to evaporate
  • A blockage in a pipe can lead to capillary action absorbing water from the toilet
  • Wind from outside the house may even be getting into the pipes and causing water to leave the bowl
  • Water may be passing through the pipe with too much force

The quickest potential fix for this and its resulting odor is to walk around your home with a pitcher full of water and pour water down every drain you have. Flush any toilets that haven’t been used in a while.

Fix Rotting Or Cracked Pipes

Your plumbing system might be in dire need of repair, particularly if it is an antiquated cast-iron pumping system. Cast-iron piping has always been very durable, but if there is cast-iron piping in your home, take it as a sign that your plumbing system is pretty old. Cast-iron plumbing was built to last 80-100 years and is reaching the end of its lifespan in many homes, according to these plumbing experts.

Rotting or cracked pipes will also often lead to leaks. If you notice that your water bill is unexpectedly high, the culprit could be a leak somewhere in your plumbing. In this case, you may want to consider hiring a qualified plumber to perform a plumbing inspection to check for leaks in the pipes.

Replacing a Missing Cleanout Plug

If a cleanout plug is missing from underneath a floor drain in your home, you may notice a sewage-like odor being emitted. Your toilet may not be the problem.

Fortunately, replacing a cleanout plug is an easy and affordable repair.  Cleanout plugs, such as this one, generally come at a low price. To install a new cleanout plug:

  1. Pull up the drain cover from the drain.
  2. Locate the two holes inside the drain bowl.
  3. One of those holes should have a cleanout plug inside it. If you don’t see a cleanout plug there, install a new plug to keep gases from escaping your sewer.

Fixing a Cracked Toilet Bowl

If you have replaced the wax seal and still have troubles with foul odors after flushing, a cracked toilet bowl is a likely culprit.

A cracked toilet bowl may or may not be accompanied by a leak, as sometimes these cracks are in hard-to-see places underneath the toilet bowl. Look for cracks around the toilet bowl or cracks within the toilet tank. Regardless of where the crack is located, you will use the same materials and methods to fix the crack.

Unfortunately, the most practical solution when you notice a crack in the toilet bowl may be to replace the entire bowl. Short of replacing the entire toilet, you may perform a repair that will buy you extra time. However, in all likelihood, you will eventually end up having to replace the toilet. A repair could last a while, though, on a toilet that does not receive too much heavy use.

To repair a cracked toilet bowl, you’ll need:

You will repair the crack using the following steps:

  1. Turn off the water supply to the toilet by turning the valve located beneath the toilet tank.
  2. Lay down towels and/or washcloths on the bathroom floor around the toilet to keep the floor from getting damaged.
  3. Drain all the water out of the tank. This can be accomplished by flushing after turning the water supply off. You may have to manually drain the toilet tank and toilet bowl by lifting the flapper located over the drain in the toilet bowl.
  4. Apply the plumber’s putty or silicone sealant on hairline cracks; more serious damage will require you to replace the toilet.
  5. Allow the putty or silicone to properly adhere to its spot based on the time duration recommended by the manufacturer.
  6. Turn the water supply to the toilet back on.
  7. Allow the toilet tank to refill.

Check to see that the problem fixes leaks or helps get rid of foul odors. If not, then you will need to proceed to troubleshoot for another potential cause. You may even need to replace the toilet entirely.

How to Find a Qualified Plumber If You Need One

In the event that your toilet problem requires the expertise of a professional, you have resources at your disposal to connect with a qualified plumber.

Be wary of contractors performing shoddy work. Many states or locales require more plumbers to hold some kind of a contractor’s license for plumbing. Contractors holding a plumber’s license likely had to take and pass an exam to receive their license or certification.

You can find out if your state or municipality requires commercial contractors to hold a plumbing license by searching terms such as “plumber’s license in….” followed by the name of your state or locale.

There are also numerous online review sites for local contractors, including Google Reviews, HomeAdvisor, and Angie’s List.