A sewer scope is a visual inspection: it shows the inside of the pipe but not whether it leaks under pressure or what else drains into it. Three tests fill those gaps. Dye testing traces where a fixture, downspout or sump actually discharges. Smoke testing reveals broken pipes, open cleanouts, dry traps and improper connections. Air or water pressure testing checks that new or repaired pipe is watertight before it is buried.
- A camera shows condition; it cannot prove a pipe is watertight or reveal every connection into it.
- Dye tests answer 'where does this water go?' and are cheap and quick.
- Smoke tests are mostly run by municipalities on whole streets; smoke from roof vents is normal, smoke indoors is not.
- Pressure tests are used on new or repaired piping before it is covered, as the plumbing inspector directs.
- The camera and these tests work best together: the camera finds where to look, the tests confirm what is happening.
01 /What is sewer scope testing, and what can a camera not test?
Sewer scope testing usually just means the camera inspection itself: a video survey that records the inside of the pipe. It is an observation, not a test in the engineering sense. A camera can see a crack, but it cannot tell you how much water leaks out through it, whether a hairline joint gap lets groundwater in during spring, or whether a downspout somewhere is connected to the sanitary line.
| Question | Can the camera answer it? | Better tool |
|---|---|---|
| Are there roots, cracks, offsets or sags? | Yes | Camera |
| Where exactly is the defect and how deep? | Yes, with a sonde locate | Camera and locator |
| Is the pipe watertight? | No | Air or water pressure test |
| Is a downspout, sump or area drain connected to the sanitary sewer? | Sometimes, if the connection is seen | Dye test |
| Where is sewer gas getting into the house? | Rarely | Smoke test of the drain-waste-vent system |
| Which main does the house drain into? | Sometimes | Dye test with manhole observation |
| Is groundwater entering through a joint? | Only if actively running when filmed | Camera in wet season, or flow monitoring |
02 /How does a dye test work?
A dye test works by putting a strongly coloured, non-staining tracer dye into one fixture or drain and watching where the colour appears. It answers one question at a time: where does this water go? It is one of the cheapest diagnostic tools in drainage work.
- Choose the source
A sink, shower, floor drain, downspout, sump pit or yard drain whose destination is uncertain.
- Add dye and flush
Dye tablets or liquid are added with enough water to carry them along.
- Watch the likely outlets
The downstream sanitary manhole, the storm manhole, a ditch, or the camera view inside the lateral.
- Record the result
Note which outlet showed dye and how long it took. A camera recording of dyed water entering at a joint is strong evidence.
- Improper connections — a downspout, weeping tile or sump connected to the sanitary sewer adds clean water that the sewer was not designed to carry, especially in storms.
- Leaks under a slab — dye in a shower drain that later shows in a floor crack or a sump points to a broken drain below the floor.
- Which sewer a house uses — useful where records are missing or where a lot might be served by a lane main or a street main.
03 /How does smoke testing work, and is it safe?
Smoke testing works by blowing a harmless, visible smoke into a sewer with a fan and watching where it comes out. Municipalities use it on whole streets to find broken laterals, uncapped cleanouts, connected downspouts and catch basins, and cross-connections. Plumbers use smaller smoke machines inside a building's drain system to find the source of a sewer gas smell.
| Smoke appears at | Usually means |
|---|---|
| Roof vent stacks | Normal; vents are open to the sewer by design |
| A crack in the lawn over the lateral | A broken or separated lateral below |
| A downspout or yard drain | That drain is connected to the sanitary sewer |
| An exterior cleanout | Missing or loose cap |
| Inside the house, at a floor drain | Dry trap; pour water in to restore the seal |
| Inside the house, from a wall or around a toilet | A leaking drain or vent pipe, or a failed toilet seal |
04 /What are air and water pressure tests for sewer lines?
Pressure tests check that a pipe holds water or air without leaking. New drainage piping is normally tested before it is covered, under the plumbing code as adopted in your province, and the plumbing inspector specifies which test and what standard it must meet. Repairs and new laterals are often tested the same way.
Pressure testing an old clay lateral rarely makes sense, because its joints were never designed to hold pressure and it would fail by design. For old pipe, the camera is the right tool; for new or repaired pipe, a test plus a post-work camera pass confirms the job. The after the inspection guide explains where a post-repair video fits.
05 /What is a sewer lateral inspection program?
A sewer lateral inspection program is a municipal effort to find and reduce clean water entering the sanitary sewer through private laterals and connections. Rain and groundwater getting into sanitary sewers, known as inflow and infiltration, takes up capacity that is needed for wastewater and can contribute to basement backups during storms.
- Street-by-street smoke and dye testing to find connected downspouts, sumps and broken laterals.
- Camera inspection of laterals from the main with lateral launch cameras; see CCTV sewer inspection.
- Programs encouraging disconnection of downspouts and sump pumps from the sanitary sewer.
- Subsidies or information programs for backwater valves or lateral repairs in some municipalities.
- In some places outside Canada, a required lateral inspection or test when a property is sold or renovated.
Programs, bylaws and subsidies differ by municipality and change over time. If you receive a notice or want to know what applies to your property, contact your municipality; in Calgary, call 311.
06 /Which test do you actually need?
Choose the test by the question you need answered. For most homeowners and buyers the camera comes first, and the other tests follow only when the camera cannot settle the question.
| Situation | Start with | Then, if needed |
|---|---|---|
| Buying a house | Camera inspection | Nothing else, unless a defect needs confirming |
| Sewer smell indoors, no visible cause | Check traps and the cleanout plug; plumber's smoke test of the drain-waste-vent system | Camera of the building drain |
| Water appearing through the basement floor after showers | Dye test | Camera of the under-slab drain |
| New lateral or repair before backfill | Pressure test as the inspector directs | Camera pass to check grade and joints |
| Suspected downspout or sump into the sanitary sewer | Dye test | Disconnect as your municipality requires |
| Municipal smoke test notice | Fill traps beforehand; report indoor smoke | Camera if smoke showed in the yard |
| After a backup | Camera inspection; see after a backup | Dye test if the source of water is unclear |
If a camera inspection is where you need to start, request a quote and mention any test results or municipal notices you already have. The camera run can then focus on the section in question.
FAQQuestions people ask
Is sewer smoke testing safe for my house?
The smoke used for sewer testing is generally described as non-toxic and non-staining, but it can be unpleasant indoors. Fill floor drain traps beforehand, ventilate if smoke enters, and tell the crew where it appeared.
Why is the city smoke testing my street?
Usually to find where rain and groundwater enter the sanitary sewer through broken laterals, uncapped cleanouts or connected downspouts, which takes up capacity during storms.
Can a camera find a leak in a sewer pipe?
A camera finds the defects that leak, such as cracks, holes and open joints, and sometimes shows groundwater entering. It cannot measure whether or how much wastewater leaks out.
What is a sewer pressure test?
A test in which a section of pipe is plugged and filled with water or pressurised with air, then watched for a drop. It confirms new or repaired pipe is watertight before it is buried.
Can my sump pump drain into the sanitary sewer?
Many municipalities do not allow sump pumps or downspouts to discharge into the sanitary sewer. Rules vary, so confirm with your municipality before changing any connection.
What is a dye test for sewer lines?
A diagnostic in which coloured tracer dye is flushed into one drain or downspout and the likely outlets are watched to see where it goes.
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