Best practices for conducting a wastewater collection system smoke test
A wastewater collection system smoke test is a practical way to locate unwanted connections, confirm suspected defects, and understand how air moves through buried pipework. When conducted carefully, it can reveal stormwater entry points, roof downpipes, yard drains, cracked laterals, open cleanouts, and other sources of inflow and infiltration without excavating streets or private property.
The method uses a blower to introduce non-toxic smoke into an isolated section of sewer. Smoke escaping from the ground, a building, a gully, or a roof drainage system indicates a connection or defect that warrants investigation. The test is a screening tool rather than a final diagnosis: dye testing, CCTV inspection, flow monitoring, or a site visit may still be needed.
Australian utilities must account for different housing layouts, older combined drainage arrangements, narrow suburban easements, and intense rainfall events. A program in Sydney’s established suburbs may encounter complex private plumbing, while work in Melbourne can be affected by clay soils, ageing assets, and local requirements under the Environment Protection Act 2017.
Public communication is equally important. Residents may mistake smoke for a fire, and smoke can enter homes through dry traps or faulty plumbing. Clear notices, arrangements for sensitive premises, and coordination with councils, fire services, traffic controllers, and facility managers help keep the exercise safe and credible.
| Activity | Good practice | Evidence to retain |
|---|---|---|
| Define the test area | Select a manageable sewer reach and confirm access points | Map, asset IDs, boundaries |
| Prepare the community | Provide notices, contact details, timing, and safety advice | Letterbox records, stakeholder log |
| Run the test | Use controlled airflow and avoid excessive pressure | Equipment settings, weather notes |
| Record findings | Photograph and classify every smoke release | GPS points, photos, defect codes |
| Verify defects | Use CCTV, dye, or plumbing inspection where needed | Follow-up reports and work orders |
Define the purpose and test boundary
Start with a specific operational question. The aim might be to identify stormwater inflow before the wet season, investigate repeated surcharge complaints, verify a suspected illegal connection, or prioritise rehabilitation in a high-infiltration catchment. A clear purpose determines the area selected, the equipment required, and the level of evidence needed.
Choose a test reach that can be isolated and safely accessed. Review sewer maps, manhole locations, previous CCTV footage, maintenance records, customer complaints, pump station trends, and rainfall-related incidents. Confirm pipe diameter, depth, material, gradient, known easements, and any links to detention systems or pressure sewer infrastructure.
The boundary should be small enough to interpret accurately. Testing an entire suburb may produce confusing results because smoke can travel through interconnected lines. Isolate tributary branches where possible, document open ends, and note any assets that cannot be reached. If the network contains unusual hydraulic arrangements, involve an experienced collection systems engineer before equipment is started.
Prepare people, property, and equipment
Advance notification should explain the date, approximate duration, visible smoke, odour, non-toxicity, and the number residents can call for assistance. Notices should reach households, businesses, schools, aged-care facilities, hospitals, strata managers, and commercial kitchens. In Australia, give extra attention to properties with rainwater tanks, backyard studios, granny flats, and informal drainage modifications.
Ask occupants to pour water into infrequently used floor wastes and sinks so traps contain water. Identify people with respiratory sensitivities and arrange a different testing time where practical. Inspectors should never assume that a private building’s plumbing complies with current standards. Smoke entering a building is a finding to be managed, not evidence that the resident caused the problem.
Use a suitable blower, smoke cartridges or liquid smoke approved for the application, plugs, barriers, radios, high-visibility clothing, gas detection equipment where required, and cameras or tablets for records. Check calibration, batteries, hoses, seals, and access covers. Smoke products must be handled according to the manufacturer’s safety data and site risk assessment.
The work area also needs traffic and public safety controls. Manholes may be located in busy roads, laneways, shopping strips, or school zones. Follow the relevant state or territory traffic guidance, safe work procedures, and confined-space controls. No person should enter a sewer solely because a smoke test is underway.
Coordinate with businesses and regulators
Commercial premises often have drainage arrangements that are more complicated than residential properties. Restaurants, cafés, pubs, food manufacturers, and shopping-centre kitchens may have grease arrestors, trade waste connections, private pump wells, or roof drainage routed through service corridors. Reviewing FOG management guidance can help inspectors distinguish a sewer defect from a maintenance problem inside a food business.
Contact the water authority and council before testing where approvals, permits, or notification rules apply. Requirements vary between states and utilities. For example, a program affecting a Sydney Water network may need coordination with the utility’s access and operational processes, while a Victorian project may need to align with council procedures and duties under environmental protection legislation.
Fire and emergency services should be advised when the area, timing, or smoke volume could generate public concern. Notify shopping-centre security, building managers, and industrial site supervisors. A simple briefing should identify the test streets, the appearance of the smoke, the product used, and the person responsible for responding to calls.
Plan for weather and local habits. Strong wind can disperse smoke and make results unreliable, while heavy rain can alter drainage behaviour. Early morning testing may avoid peak traffic but can disturb residents; testing around school drop-off times or busy weekend trading can create unnecessary risk. Select a period that balances visibility, access, and community impact.
Control the smoke test in the field
Before introducing smoke, inspect each access point and confirm the intended isolation. Place plugs or temporary barriers carefully, preserving safe pressure relief. Start the blower at a low setting and increase airflow gradually. Excessive pressure can force smoke through traps, damage weak seals, or create misleading releases that would not occur under normal sewer conditions.
A competent observer should walk the test area while another person controls the blower and records observations. Look for smoke at stormwater pits, grated drains, downpipes, roof gutters, inspection openings, garden drains, retaining walls, cleanouts, and pavement cracks. Take photographs from a useful distance and record the exact address, asset reference, weather, time, and apparent source.
Smoke seen at a property does not always identify the precise defect. It may travel along fill, utility trenches, porous ground, or interconnected private drainage. Note the strength, duration, and location of each plume. A brief wisp from a vent may be normal, whereas a persistent release from a rainwater inlet suggests a direct cross-connection or failed separation.
Stop the operation if unexpected pressure, damaged infrastructure, unsafe traffic conditions, chemical exposure, or public distress develops. Ventilate buildings when necessary and provide clear advice to occupants. The field team should have a stop-work authority and a procedure for reporting incidents immediately.
Interpret results and verify defects
Classify findings consistently so the results can support maintenance and capital planning. Useful categories include direct stormwater connection, indirect inflow source, defective private lateral, open cleanout, damaged public sewer, unsealed manhole, illegal connection, and inconclusive observation. Use agreed defect codes and confidence ratings rather than relying on free-text descriptions alone.
Follow-up testing is important because smoke only shows a pathway for air. CCTV can assess structural condition and root intrusion, while dye testing can confirm whether a roof, yard, or surface drain reaches the wastewater network. Flow monitoring before and after rainfall can quantify the effect of a suspected inflow source.
Link observations with customer records, rainfall data, pump station alarms, and maintenance history. Repeated wet-weather alarms may justify faster investigation of a catchment, while a single smoke release in a dry-weather area may be a lower priority. Predictive maintenance can be strengthened by combining inspection results with pump failure analytics, particularly where inflow contributes to wet wells, ragging, or excessive pump starts.
Respect privacy when recording private property. Capture only what is needed to identify the drainage issue, protect photographs and addresses, and restrict access to authorised staff. Residents should receive a clear explanation of the finding and the responsible authority, especially when corrective work falls to a private owner.
Turn findings into an enforceable work program
Rank defects by environmental risk, public health significance, recurrence, hydraulic impact, and ease of correction. A direct stormwater connection to a sewer that surcharges near a creek may deserve urgent action. A minor inaccessible defect can be scheduled with other renewal work, provided the risk is documented and monitored.
Assign ownership and deadlines for every verified issue. Public assets may require cleaning, sealing, relining, or reconstruction. Private defects may involve a plumbing notice, trade waste discussion, technical advice, or cost-sharing arrangement, depending on local rules. In Australian communities, practical assistance and plain-language explanations often achieve better cooperation than enforcement alone.
Use results to improve the wider program. Update GIS layers, asset registers, defect histories, and catchment inflow models. Compare smoke findings with CCTV condition scores and wet-weather flow data. If a suburb has recurring grease-related blockages, pair the inspection program with education for food businesses and regular servicing of grease arrestors.
Keep a documented response plan for any sewage release discovered during testing or subsequent investigation. The guidance on spill response planning can support roles, escalation paths, notifications, containment measures, and post-incident review. The immediate next step is to select one high-priority sewer reach, complete its asset and stakeholder review, and issue a dated field plan for the smoke test.