Sewage Smell From Bathroom:
6 Possible Reasons and Fixes
If you’ve recently noticed a strong sewage smell from your bathroom, you’re not alone. Many Toronto homeowners experience this unpleasant issue at some point and it’s not just a nuisance. A bad odour can be a warning sign of underlying plumbing issues. A foul smell in your bathroom, often referred to as a sewer smell in the bathroom, can indicate a serious problem in your plumbing system, from a clogged shower drain to a dangerous sewer gas leak.
This article explores six common causes of sewer smells in bathrooms and sewerage odours as a common problem and what you can do about them. Whether you’re dealing with sewer odours in a guest bathroom or experiencing recurring sewage smells from a bathroom sink, John The Plumber Downtown Toronto is here to help you regain a clean-smelling bathroom.
1. Dry or Faulty P-Trap
Potential Risk
Moderate
DIY Friendly
Yes
Plumber Required
Sometimes
The P-trap (also known as a U-shaped pipe or water trap) beneath your sink or shower drain is designed to trap water and block sewer gases from entering your home. The P-trap is essential to prevent sewer gases and unpleasant odours from entering the bathroom. When that trap dries out, often due to infrequent use in guest bathrooms, it creates a direct path for sewage gases to rise into your living space.
Solution: Run hot water for a few minutes to refill the trap, ensuring there is sufficient water in the P-trap to maintain the seal. To prevent the trap from drying again, run water through all bathroom drains weekly. If the smell persists, your P-trap may be cracked or improperly installed and will require inspection by a licensed plumber.
2. Clogged Shower Drain or Sink Drain
Potential Risk
Low to Moderate
DIY Friendly
Yes
Plumber Required
Occasionally
Soap scum, hair, and debris create a breeding ground for bacteria inside your shower drain and sink drain. Shower drains are a common source of clogs and odours. This can generate a foul smell that resembles rotten eggs due to the presence of hydrogen sulphide, a byproduct of bacterial activity and sewage.
Fixes you can try:
- Pour a cup of baking soda and vinegar down the drain.
- Use a drain snake (or plumbing snake) to remove physical blockages.
- Consider a professional drain cleaning if odours return.
DIY solutions like baking soda and vinegar are effective for clearing clogs and odours in shower drains and sink drains.
Persistent blockages may indicate issues deeper in the main sewer line, which calls for a professional plumber’s expertise.
3. Damaged or Loose Toilet Seal (Wax Ring)
Potential Risk
Moderate
DIY Friendly
No
Plumber Required
Yes
Your toilet connects to the floor with a wax seal that keeps sewer gas and waste contained. Over time, this toilet seal can degrade, crack, or shift, allowing gases and even sewage backup to leak into your shower room.
What to do:
If you notice a sewage smell around the toilet bowl, wobbling, or water pooling at the base, contact a professional plumber. Replacing a wax ring involves removing and reseating the toilet, something best handled by an expert to avoid further plumbing damage.
4. Sewer Gas Leak or Vent Pipe Issue
Potential Risk
High
DIY Friendly
No
Plumber Required
Absolutely
Your vent pipe equalizes air pressure in your sewer system and routes gases like hydrogen sulphide safely outside. If it becomes cracked, clogged, or improperly installed, sewer gas may be redirected into your home, causing a noticeable sewer gas smell and exposure to sewer gases, which can be hazardous and lead to dangerous health risks like hydrogen sulphide poisoning.
How plumbers diagnose this:
- Smoke test using a smoke machine to detect hidden leaks
- Camera inspections in your vent and drain lines
If you suspect a sewer gas leak, avoid masking the unpleasant smell with air fresheners and instead call a master plumber immediately.
5. Septic Tank or Sewer Line Problems
Potential Risk
High
DIY Friendly
No
Plumber Required
Yes
While many homes in Toronto are connected to the municipal sewer system, some older or rural properties use septic tanks. If the septic system is full or the sewer line is blocked or cracked, you may experience sewage backup and powerful sewage odours inside your bathroom. Sewer backups can cause pipe damage and may be due to tree roots infiltrating the pipes.
Signs include:
- Gurgling sounds in drains
- Wastewater pooling in the yard
- Slow drains across multiple fixtures
- Unpleasant odours may also indicate septic tank or sewer line issues
6. Bacterial Growth in Bathroom Plumbing
Potential Risk
Low
DIY Friendly
Yes
Plumber Required
Optional
Bathrooms are warm, moist environments ideal for bacteria to thrive, especially in neglected areas like the overflow holes of a bathroom sink. This often causes that musty or unpleasant odour to linger in your bathroom.
Simple prevention tips:
- Clean all bathroom drains monthly using hot water and baking soda
- Regularly flush the toilet bowl and run taps to circulate fresh air
- Schedule annual drain cleaning by a local professional
How to Prevent Sewage Smells in Your Bathroom
- Use all your bathrooms regularly to prevent dry P-traps
- Keep your sewer lines and vent pipes maintained
- Schedule routine drain and sewer cleaning
- Regularly check your water supply for leaks or issues that could contribute to odours
- Hire licensed plumbers for annual inspections and maintenance of your bathroom plumbing
- Avoid flushing non-degradable materials
- Have your septic system or sewer connection inspected yearly
When to Call a Plumber in Downtown Toronto
If your bathroom smells like sewage and the issue isn’t resolved by DIY methods, don’t take chances. Sewer gas is hazardous, and small issues can quickly become expensive plumbing emergencies.
At John The Plumber Downtown Toronto, our certified technicians use the latest leak detection, smoke testing, and camera inspection tools to diagnose and fix sewage smell problems quickly and effectively.
Breathe Easy with a Clean Smelling Bathroom
Don’t let a foul bathroom odour ruin your peace of mind. Whether it’s a dry P-trap, cracked pipes, or a sewer backup, our Downtown Toronto plumbing specialists are ready to help you reclaim a fresh and healthy home.
Contact John The Plumber Downtown Toronto today for reliable, fast, and affordable sewer odour solutions.
Frequently Asked Questions About Sewage Smells in Bathrooms
How do I stop sewage odour in the bathroom?
How to tell where sewer smell is coming from?
The source of the sewer smell can often be narrowed down by its location. A smell near the toilet bowl may mean a damaged wax ring. Odours from the drain could point to a clogged shower drain, bacteria, or a dry P-trap. A smoke test conducted by a plumber can help identify cracked pipes, sewer gas leaks, or faulty vent pipes.
