When there is a sewer odour

A sewer-like smell noticed inside or outside.

SewerOwner does not assess air quality, gas concentrations, or health effects, and will not tell you whether a building is safe. If anyone feels unwell, contact medical or emergency help rather than reading further.

What this page cannot establish

noticing this establishes that you noticed it — it does not establish a cause
this page cannot establish what is producing the smell
this page cannot establish whether any gas is present or at what concentration
this page cannot establish whether the building is safe to occupy
this page cannot establish that the buried line is involved

What a professional will be trying to work out

These are the distinctions a professional makes when they attend. They are questions, not conclusions — and knowing them lets you follow the conversation rather than just receive its result.

where the smell is noticed and whether it moves
whether it is constant or intermittent
whether it coincides with weather, water use, or time of day
whether any fixture in the area is rarely used

What is worth writing down

These details are cheap to record now and impossible to reconstruct later.

where the smell is noticed
when it is present and when it is not
whether anything changed in the building recently

Evidence that would change the next decision

If you are deciding whether something is worth paying for, these are the things that actually move the decision.

the specific locations where it is and is not noticed
the pattern over time

What would change the answer

the specific locations where it is and is not noticed
the pattern over time

What to do next

Where and when a smell occurs is the information a professional needs, and it is best captured before it changes.

Prepare what to tell a licensed professional

If your situation is different

You also have slow or backing-up drains: More than one drain affected

What we cannot determine
Air quality and health effects are firmly outside what this platform will assess.
Smoke testing
The method usually used to trace where an odour path runs, and what it does not cover.
Gurgling
Both can point at how the system is venting rather than at a blockage.