The short answer
Start with Your Own Senses
Before any equipment is used, the pros rely on the most obvious clue: the smell. Sewage has a distinct, sulfurous odor that lingers and intensifies near the source. You might notice it first near baseboards, outlets, or vents. That smell often points to where the wall needs closer checking.
Your eyes help too. Look for yellow or brown stains, bubbling paint, or soft drywall. These marks can appear days before the odor becomes strong. In dry climates, surface stains may dry and become less obvious, so pay attention to subtle changes in color or texture.
Use Moisture Meters for Clues
Moisture meters are handheld tools that measure dampness inside building materials. The pros press them against the wall surface and get a reading. A high reading in one spot suggests water is present, but it does not tell you if that water is sewage. That distinction matters for safety and cleanup.
The pros use these meters to map out the wet area. They check the wall at different heights and distances from the suspected leak. This helps them find the boundaries of the problem. It also helps them decide where to open the wall for a closer look.
- Pinless meters scan without touching the surface
- Pin-type meters poke small probes into the drywall
- Readings above normal moisture suggest a hidden leak
- The pros compare readings across the wall to find patterns
- Moisture alone does not confirm sewage, so further checks are needed
Thermal Imaging Finds Cool Damp Spots
Thermal imaging cameras show temperature differences on a wall surface. Wet areas often cool the wall through evaporation, so they appear as cooler patches on the camera screen. This helps the pros see the shape and size of the damp zone without tearing anything open.
The camera is useful for finding leaks behind tile, paneling, or thick paint. It does not detect the sewage itself, only the moisture that comes with it. That is why the pros pair thermal imaging with other methods to confirm what the water contains.
Trace the Odor to Its Source
The pros use their noses as a detection tool, but they do it carefully. They follow the strongest smell, moving along the wall and checking at floor level and ceiling height. Sewage gases can rise, so the source might be lower than where you first notice the odor.
They also check nearby fixtures like toilets, sinks, or floor drains. A cracked pipe, a loose seal, or a blocked vent can push sewage into the wall cavity. Tracing the smell helps the pros narrow down which pipe or joint is failing.
- Check the base of the wall where it meets the floor
- Look behind removable access panels
- Sniff around electrical outlets and light switches
- Inspect the ceiling if the smell is stronger above
- Follow the odor to the nearest plumbing fixture
- Open wall cavities only when the source is close
Confirm with Sampling and Inspection
Once the pros locate a wet area, they confirm whether it is sewage. They may take a small sample of the moisture or the wall material for laboratory testing. That test checks for bacteria or chemical markers that are specific to sewage. This step protects your health and guides the cleanup.
The pros may also open a small section of the wall to see the inside. They look for black sludge, stained insulation, or corroded pipes. Seeing the actual condition tells them how far the contamination has spread and what needs to be removed. This inspection is the basis for any repair work.
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Call Now (208) 729-2441Frequently asked questions
Can I detect sewage in the walls myself?
You can notice the smell, stains, or soft spots, but you cannot confirm sewage without testing. Moisture meters and lab tests are needed for certainty. If you suspect sewage, avoid touching the area and call a local water damage pro for an inspection.
Is sewage in the walls dangerous to breathe?
Sewage contains bacteria, viruses, and gases that can be harmful if inhaled or touched. You might feel unwell from the fumes. If you feel sick, see a doctor. Keep the area ventilated and do not disturb the wall until a professional checks it.
What happens after the pros find the sewage?
The pros will explain what they found and recommend next steps. That often includes removing contaminated materials, cleaning and sanitizing, and drying the structure. Your insurance company may be involved, but policies vary, and your insurer decides what is covered.