CCTV drain inspection is the primary tool for assessing pipe condition from the inside. But CCTV has limits, it shows the pipe wall, not where gas or liquid escapes between the drain and the outside world. Smoke testing is a complementary technique that identifies leaks, illegal connections and cross-connections by filling the drain system with visible non-toxic smoke. On the Central Coast, it is used both by council inspectors for public infrastructure and by private plumbers for complex residential and commercial diagnosis.
Quick answer (BLUF)
Smoke testing fills a drain system with a harmless coloured smoke under low pressure. Smoke emerging from unexpected locations, garden soil, a vent pipe in the wrong location, a stormwater outlet from what should be a sealed sewer system, identifies leaks, illegal cross-connections or failed joints. It is particularly useful for diagnosing intermittent sewer smell problems, suspected cross-connections between sewer and stormwater, and drainage complaints in older Gosford and Wyong properties where the original drain layout is unknown.
How smoke testing works
The process is straightforward in concept:
- All accessible drain openings are sealed, cleanouts, floor drains, roof vents
- A smoke machine is connected to the drain system at a convenient access point
- Low-pressure non-toxic smoke (a white or grey theatrical-style smoke) is forced into the drain
- The system is pressurised gently and then observed for 10-20 minutes
- Any location where smoke emerges identifies a breach, leak or unintended connection
The smoke used is food-grade or purpose-made for drain testing, it is non-toxic, non-flammable and dissipates rapidly. No permanent residue is left in the pipes or on surfaces. The smoke density makes even a small joint gap or pinhole crack visible.
What smoke testing can find
Joint leaks and pipe cracks: If a terracotta joint has opened or a pipe has a hairline crack, smoke will emerge from the soil surface above that point. In a tight, well-sealed drain run, no smoke escapes.
Cross-connections between sewer and stormwater: A cross-connection is where the sewer system is accidentally connected to the stormwater system or vice versa. This is prohibited, stormwater discharging to the sewer overloads the treatment plant; sewage discharging to stormwater is an environmental pollutant. Smoke testing a sewer line will cause smoke to appear from stormwater outlets or pits if there is a cross-connection, immediately identifying the location.
Illegal connections: Properties with extensions, additions or modified drainage (common in older Gosford and Wyong homes that have been extended without formal documentation) may have connections that were never approved and are not reflected in any drainage plan. Smoke testing locates these quickly.
Failed inspection shaft seals: If an old terracotta inspection shaft has lost its lid seal, or a concrete pit has a cracked wall, smoke will emerge from ground level at that point.
Internal venting failures: In multi-storey buildings, smoke testing can identify ventilation failures in the drainage system that cause trap syphoning and persistent sewer gas smell inside.
When to use smoke testing vs CCTV inspection
CCTV inspection and smoke testing answer different questions:
| CCTV inspection answers | Smoke testing answers |
|---|---|
| What does the inside of the pipe look like? | Is the pipe system sealed to the outside? |
| Where are the root infiltrations? | Where are the leaks? |
| Is there a collapse or deformation? | Are there illegal cross-connections? |
| What is the pipe material? | Where does the drain run (approximate)? |
In complex diagnostic situations, both techniques may be used, CCTV to map defects and smoke testing to confirm whether those defects are actually causing leakage to the environment.
Smoke testing on the Central Coast: common scenarios
Persistent sewer smell with no obvious cause: The homeowner can smell sewer gas inside or in the garden but the CCTV inspection shows no blockage or visible defect. Smoke testing identifies whether the smell is coming from a joint leak, a failed inspection shaft seal or a vent pipe termination point that is too close to the building.
Pre-purchase due diligence on an older property: Some buyers and buyers’ agents in areas like Woy Woy, Gosford and The Entrance are now requesting smoke tests as part of pre-purchase drain due diligence, particularly for properties where the drainage layout is unclear from available records.
Council infrastructure investigation: Central Coast Council’s drainage operations team uses smoke testing to identify private stormwater connections that are illegally discharging to the sewer, and to trace infiltration issues in the public stormwater network. A council-initiated smoke test on a street section may result in notices to affected property owners.
Before subdivision: Confirming that a property’s existing drainage has no cross-connections before subdivision lodgement reduces the risk of consent conditions requiring remediation after approval.
What happens after smoke testing finds a problem
If smoke testing identifies a joint leak, crack or cross-connection, the next step depends on the nature of the finding:
Joint leaks and pipe cracks: CCTV inspection to confirm the exact location and severity, followed by point repair or full-length relining as appropriate.
Cross-connections: These require active remediation, the illegal connection must be physically cut and properly sealed. Simply relining the pipe does not fix a cross-connection.
Illegal connections to the sewer: The local water authority (Sydney Water or Hunter Water) may require formal notification and an approved rectification plan.
Council-initiated investigation finding issues on your property: You will typically receive a notice requiring rectification within a specified timeframe. A licensed plumber can manage the rectification process.
FAQs
Is smoke testing harmful to people or pets?
The smoke used for drain testing is non-toxic and non-flammable. It is essentially a theatrical-style fog machine fluid. It disperses in air within minutes and leaves no residue. No evacuation of the property is required, though people with respiratory sensitivities may prefer to remain outside during the test.
How much does smoke testing cost on the Central Coast?
Smoke testing as a standalone diagnostic typically costs $300, $600 for a residential property, depending on the complexity of the drain system. It is often more cost-effective when bundled with a CCTV inspection, some contractors offer combined inspection packages.
Will smoke testing damage my plants or garden?
No. The smoke dissipates within minutes and has no chemical impact on soil, plant material or groundwater. You may see white or grey smoke emerging from the garden surface above a leaking joint, this is the point of the test.
Can smoke testing locate where the stormwater pipe runs if I have no drainage plan?
To an extent. If smoke escapes from the ground surface along the pipe route, the approximate line of the drain can be traced. However, smoke testing is not a precision pipe-location technique, it shows leaks rather than mapping intact pipe runs. Ground penetrating radar (GPR) or a CCTV camera with a sonde locator is better for precise pipe mapping.