5 Star Plumbing | Bad Smell Coming From Toilet: 9 Most Common Causes & Solutions
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Bad Smell Coming From Toilet: 9 Most Common Causes & Solutions

5 Star Plumbing > Blog > Bad Smell Coming From Toilet: 9 Most Common Causes & Solutions

Whatever its name, bathroom odor is always unpleasant and could even be deadly. A deep clean, where every nook and cranny has been cleaned, may be necessary when bathroom odors have built up and your standard air freshener is failing to eliminate the foul smells. This is one method for addressing the problem.

A stinky toilet could also be a sign of a more serious plumbing issue that requires expert attention and requires more than a DIY fix like baking soda, bleach, lemon juice, essential oils, white vinegar, or a cup of vinegar and hot water.

Why does the odor smell bad?

We regrettably lack a conclusive solution because there may be a lot of causes, and without being present, it may be challenging to identify the source of the offensive smell.

In addition to having an unpleasant odor, sewer gas contains methane, which is frequently linked to bathroom odors and that “bad smell” that the exhaust fan is unable to eliminate. Methane is not only flammable in high quantities, but it is also unhealthy to breathe.

The good news is that after you figure out what’s causing the odor, fixing it shouldn’t be too expensive or complicated. A sewage smell in your bathroom indicates that something is wrong with the plumbing system.

Possible reasons are:

  • The water in the shower, tub, or P-trap (sink) has evaporated.
  • A leak in the P-trap or nearby.
  • Obstructed drain.
  • The toilet seal is broken.
  • Restricted roof vent.
  • A vent pipe was installed incorrectly.
  • Vent pipe with a crack.

P-Trap with Evaporated Water

The P-trap in a toilet sometimes contains water that has evaporated, which is a common cause of unpleasant odors. To stop smelly sewage gases from entering the bathroom, the P-trap is a U-shaped conduit that is located beneath the toilet bowl. It captures water.

When a toilet isn’t used for a long time, the water in the P-trap evaporates, allowing sewer gases to escape and produce unpleasant odors. Vacant guest rooms or vacation homes frequently experience this issue.

Running water through the toilet on a regular basis will fill the P-trap and stop evaporation. Alternatively, a thin layer of mineral oil can be added to the water to form a barrier that slows the evaporation process.

schema trap

How to fix it

To ensure that the P-trap continues to trap and keep gases from entering your home, flush your toilet a few times to refill it with water.

Clogged Toilet Drain or Pipe

A clogged toilet drain or pipe might be a significant contributor to the unpleasant smell coming from your toilet. When waste, toilet paper, and other debris build up in the drain or pipe, they block the flow of water and make it stagnate. The odor-producing bacteria that are produced as a result of this stagnation can cause a foul toilet smell.

Having an outdated plumbing system that is prone to clogging, or flushing improper stuff down the toilet are just two examples of causes for clogs that can happen. Tree roots may occasionally enter pipes, clog them, and cause foul odors. Utilizing your toilet correctly and performing routine maintenance can help prevent clogs and keep it smelling fresh.

How to fix it

To have the seal changed, contact a licensed plumber. Our 5-star plumbers are available in different locations.

The tank has little water in it

A key contributor to a foul-smelling toilet is the low water level in the toilet tank. When the water level in the toilet tank is too low, it can cause insufficient flushing and a buildup of waste and bacteria.

This problem may be brought on by a number of things, including a broken or clogged pipe, a troublesome toilet flapper, a dirty toilet tank, or an inoperable water valve. Hard water can also result in mineral accumulation on toilet tank parts, which lowers the water level.

Unclogging the pipe, replacing the toilet flapper, or adjusting the water valve may be required to resolve this problem. Low water levels and bad aromas in your bathroom can be prevented with regular cleaning and upkeep.

How to fix it

Follow these steps to modify the float:

  • Verify the kind of float you have.
  • If you have a big rubber ball gadget in the tank, adjust the float ball’s arm slightly upwards so that more water can get in.
  • Or, turn the float adjustment screw (sometimes referred to as the floating cup ballcock) clockwise to elevate the float if it is located on top of the fill valve.

If neither of these solutions succeed, get assistance from a licensed plumber.

The toilet's flapper isn't operating properly

Bad smells may result from a malfunctioning toilet flapper. The flapper is in charge of controlling how much water is pumped from the tank into the bowl. If it breaks, water may leak from the tank, leaving the toilet bowl dry and allowing a sewage smell to enter the room.

If the flapper is damaged, worn out, or installed incorrectly, it may not function properly. It is crucial to take care of this problem right away to stop the foul odor from persisting. The issue can be resolved easily and affordably by changing the flapper. Regular cleaning and maintenance can also stop problems from developing in the first place.

How to fix it

You can adjust the flapper’s chain by detaching it and rehooking it to a hole closer to your flush lever. Make sure the chain has just the right amount of slack so that when you flush the toilet, it opens completely.

You should replace your flapper if it is too old or damaged. If you need to replace the flapper or its chain, call a plumber.

Bacteria in the System

A typical explanation for unpleasant scents coming from toilets is bacteria in the system. This occurs when organic waste and waste-related gases, such hydrogen sulfide, which has an odor similar to rotten eggs, are broken down by natural bacteria in the toilet’s pipes and drains.

This issue can be made worse by other things, including infrequent toilet usage, inadequate ventilation, and low water levels. When certain bacteria accumulate in the bowl or tank, they can also produce unpleasant odors.

This problem can be avoided by performing routine toilet cleaning and maintenance, as well as by utilizing substances that encourage the growth of beneficial bacteria.

How to fix it

Make a bleach solution with water in it:

  • Put on a mask, rubber gloves, and a waterproof apron before mixing one capful of bleach (5% sodium hypochlorite) with 99 parts cold tap water.
  • Do this in a space that has good ventilation.
  • Do not mix this diluted bleach with additional toilet cleaning products. (If necessary, first use detergents, then thoroughly rinse the area with water before applying the diluted bleach.)
  • After 24 hours, throw away the diluted bleach; do not use it again.
  • Remove any undesirable microorganisms from the bowl:
  • Fill the tank’s overflow line or flush valve with the diluted bleach.
  • After waiting for 30 minutes, flush your toilet to allow the bleach out and get rid of the bacteria and odor.

Mold Buildup

One of the main causes of bad toilet smell is mold buildup. Toilets are the ideal growing habitat for mold since it prefers warm, damp surroundings. As a result, the bathroom may begin to emit unpleasant smells.

When the toilet is not properly aired, or is not cleaned frequently, mold growth happens. When you flush and take a shower, the moisture and humidity can create the ideal conditions for mold to grow. Mold growth can also be facilitated by toilet leaks, which can also be a factor.

Regular toilet cleaning and ventilation are essential for preventing the growth of mold. A window can be opened or an exhaust fan can be used to accomplish this. In addition, any toilet leaks need to be corrected right away to stop moisture from building up.

How to fix it

For mold removal, use respiratory protection. Use an old toilet brush and either white vinegar or bleach to scrub the bottom of the rim. Additionally, any feces that might have splashed onto the rim will be removed as a result. Keep in mind to also clean the toilet seat’s underside.

Vent Pipe Problem

An attached vent pipe that passes through your roof serves as a common method of toilet drainage. To ensure that wastewater flows swiftly through the pipes and into the main sewer line, the pipe ventilates the system, eliminates sewer gas, and allows air to enter the system.

Sewer gas won’t be able to escape if this vent clogs due to obstructions or bad design.

How to fix it

For example, a nest of birds or a mass of leaves can obstruct the vent pipe. To clear it and inspect the vent pipe’s shape, call a licensed plumber.

To prevent sediments and liquids from being lodged inside the vent pipe, it should have a downward slope. A professional plumber should replace the vent pipe if the slope isn’t steep enough to prevent toilet water from stalling every time you flush after it encounters the obstruction.

A damaged sealant ring is present in the toilet

Your bathroom may smell bad if your toilet has a broken sealing ring, commonly known as a wax ring. The wax ring forms a watertight barrier between the toilet base and the sewer pipes. If the wax ring is worn out or damaged over time, sewage gas can escape through the crack and produce an odor.

Age, regular usage, faulty installation, or an unstable toilet base are just a few of the things that might harm the sealing ring. A quick and low-cost remedy to this issue is to replace the wax ring. To avoid further damage and potential health risks, it is better to treat the problem as soon as you notice a persistent bad smell.

How to fix it

Check for fractures in the sealing ring. Apply caulk to the exposed area if there are cracks.

No cracks are visible? Verify whether your toilet shakes or wobbles. If this is the case, a plumber needs to be hired to replace the loose sealing ring.

Cracked Toilet

Bathroom smells can be brought on by a damaged toilet. It happens when a crack forms in the porcelain or ceramic of the toilet, allowing sewer gases to seep into your bathroom. This may occur as a result of aging, poor installation, or physical damage.

Your health could be harmed by the offensive odor, which needs to be removed right away. Leaving a broken toilet unattended might result in water damage and other plumbing problems. It’s recommended to call a licensed plumber for repairs if you smell anything nasty coming from your toilet.

How to fix it

A crack above the waterline may be repairable, but if the damage is minor, you’ll likely need a new toilet to get rid of the sewer gas smell.

Additional Suggestions for Eliminating Toilet Odor

There are a few additional ideas for removing a toilet smell in addition to the conventional cleaning techniques. One is to use a toilet-specific odor-neutralizing product, such as deodorizing tablets or toilet bowl cleaners. Opening a window or putting on a fan will improve airflow in the bathroom.

Additionally, odors can be prevented from developing in the first place by routinely maintaining your plumbing and septic system. Consider contacting a reputable plumbing business like A-1 Sewer and Septic Service for advice and remedies if your toilet is emitting a chronic stink.


How can you get rid of the sewer odor in the toilet?

Sewer smell in a toilet might have a number of sources, such as a dry P-trap, blocked vent pipes, or a broken wax ring. To get rid of the odor, consider flushing the toilet to refill the water in the P-trap, cleaning the toilet properly, or calling a plumber to handle any bigger difficulties.

Why does my toilet have such a foul odor?

An unpleasant odor coming from a toilet could be caused by a number of things, such as a dry P-trap, clogged vent pipes, or a broken wax ring. A bacterial or mold buildup could also be to blame. A plumber can assist in identifying the problem and resolving it, which may require cleaning or fixing various components of the toilet system.

Why does flushing my toilet make the room smell like sewer?

With a dry P-trap, sewer gas can enter your home and cause your toilet to smell like a sewer when you flush. Both infrequent toilet usage and a broken vent system could be to blame for this. The problem can be identified and resolved by a plumber to get rid of the odor.

How can I get rid of my toilet's offensive odor?

Try flushing the toilet to refill the P-trap with water, properly cleaning the toilet with a disinfecting cleanser, and applying a toilet bowl deodorizer to get rid of any unpleasant toilet smells. A plumber can help identify and resolve the problem if the odor continues.

Why does my clean toilet smell bad?

If your toilet smells awful even when it is clean, it may have a broken flange or a defective wax ring that permits sewage gas to escape. It might also be brought on by bacterial or mold growth in the toilet bowl or tank. A plumber can identify the problem and resolve it.
Peter, plumber

I bring over 9 years of dedicated plumbing experience to the table. As a seasoned professional in the plumbing industry, I've tackled a wide range of projects, from residential repairs to large-scale commercial installations.

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