How to Get Rid of Sewage Smell in the Bathroom

Bad odour in the bathroom is a frequent issue in flats and older houses, yet it can also crop up in recently refurbished properties. Even after a thorough clean, a sewage smell can stubbornly linger and, in most cases, the source is somewhere within the water drainage system, the pipework ventilation, or simple sealing faults that you can often check without any major building work.

What are the most common causes of a sewage smell in the bathroom?

A sewage smell in the bathroom is usually connected to how used water is directed into the waste system. Beneath basins, showers and baths there are curved fittings (U-bends/traps) that hold a small amount of water to create a barrier against gases; when that water seal fails, odours can drift back into the room.

Soap scum, hair, toothpaste, grease and hygiene products can build up along the inside of pipes, forming a film that, over time, starts to give off a strong smell. Poor pipe ventilation, inadequate sealing around the base of the toilet, and loose joints can also allow gases to escape and cause unpleasant odours.

Watch a video on the YouTube channel O Pulo do Gato na Construção explaining how to identify bathroom odour causes linked to the trap (sifão) or the trapped floor drain (caixa sifonada), and how to fix the issue for good:

https://www.youtube.com/watch?v=qMiwKIn0N7w

How can you identify where the sewage smell in the bathroom is coming from?

To work out where the sewage smell in the bathroom is coming from, start by noticing where it is strongest: the shower drain, basin waste, floor drain, or the toilet. Using that as your guide, you can run through a straightforward set of checks, moving from the most likely causes to the less obvious ones.

These checks help you tell whether it’s a local issue-such as a dried-out trap-or something affecting the internal system more broadly. Pay attention to how the water drains away, any hidden damp, and unusual noises in the pipework, as these details often point to the source of the bad smell.

• Check drains that are rarely used and run water for a few minutes to refill the trap seal.
• Look inside drains and manually remove hair and any built-up debris.
• Examine the base of the toilet for looseness, movement and signs of damp staining.
• Inspect traps and any visible connections under the basin for cracks, drips, or loose threaded fittings.
• Listen for gurgling sounds and note slow drainage in more than one place in the home.

When does a sewage smell in the bathroom require professional help?

Not every sewage smell in the bathroom means you need a plumber, but some signs suggest it has moved beyond the basics. If the odour returns soon after you’ve refilled the traps with water, or if it appears from several drains at the same time, there may be a problem with pipe ventilation or a blockage in internal sections of the system.

Leaks into walls or floors, damp patches with no clear cause, repeated blockages and constant gurgling noises can indicate damage in concealed pipework. Because gases from organic decomposition can trigger headaches, nausea and general discomfort, a technical assessment helps pinpoint the fault using the right equipment and reduces risks to health and to the building’s structure.

How can you prevent a sewage smell in the bathroom day to day?

Keeping sewage smell out of the bathroom comes down to small routine habits that protect the water seal in traps and limit residue build-up. Using all drains reasonably often, and being careful about what goes down the basin and the toilet, makes a noticeable difference over time.

It also helps to clean visible drains regularly, fit strainers that catch hair, and watch for changes in how quickly water drains away, as these are often the first warning that something in the pipework is not right. By staying alert to these details, you improve day-to-day comfort and extend the life of the plumbing installation, avoiding unpleasant surprises and more costly work later on.