A septic system overflow, sewage reaching the surface, entering a stormwater drain, or backing up into the house, is not just an inconvenience. It’s a public health emergency, a potential environmental offence under NSW law, and something that requires immediate action. In the Port Macquarie-Hastings region’s sensitive Hastings River catchment, the stakes for a sewage spill are particularly high.
Quick answer (BLUF)
Sewage overflow poses real health risks from pathogens including E. coli, Salmonella, Hepatitis A, norovirus, Cryptosporidium and Giardia. In NSW, an overflow reaching a watercourse, stormwater system, or a neighbouring property must be reported to PMHC and potentially the EPA. Immediately stop water use, call an emergency pump-out service, contain the overflow where possible, and avoid contact with the affected area. Do not attempt to hose away surface sewage, this spreads contamination.
The health risks: what sewage contains
Untreated or partially treated sewage is a complex mix of biological hazards:
Bacterial pathogens:
- Escherichia coli (E. coli): The indicator organism for faecal contamination; pathogenic strains cause severe gastroenteritis
- Salmonella: Gastroenteritis; potentially severe in children, elderly, or immunocompromised people
- Campylobacter: The most common cause of bacterial gastroenteritis in Australia
- Clostridium perfringens: Sporadic gastroenteritis
Viral pathogens:
- Norovirus: Highly contagious; causes acute gastroenteritis; survives in the environment for days to weeks
- Rotavirus: Primary cause of severe diarrhoea in young children
- Hepatitis A virus: Liver infection; can be severe; vaccination provides protection
Protozoan pathogens:
- Cryptosporidium parvum: Resistant to chlorine disinfection; causes severe diarrhoea, particularly dangerous for immunocompromised individuals
- Giardia intestinalis: Persistent gastrointestinal illness; common in rural water supplies
The risk profile is highest for direct contact with raw sewage, consumption of water or produce contaminated by overflow, and children playing in affected soil or water.
Immediate steps: what to do in the first hour
1. Stop adding water to the system Turn off washing machines, dishwashers, and hot water. Restrict toilet use to the absolute minimum. Reducing hydraulic load can stop the overflow from worsening while you wait for the pump-out contractor.
2. Keep people, children and pets away from the affected area Establish a clear exclusion zone around any surface overflow, wet patches, or backup area. Assume the affected ground is contaminated with pathogens.
3. Call an emergency pump-out service This is a same-day emergency, communicate that clearly when you call. Emergency pump-outs are the trade norm for active overflow situations; timing is confirmed by the operator once your enquiry is reviewed.
4. Do not hose the area A natural instinct is to wash the visible sewage away with a hose. This disperses contaminated material over a wider area and drives pathogens into the soil and potentially toward drainage. Leave the area as-is until the contractor arrives and the situation is stabilised.
5. Do not enter confined spaces near the tank Open septic tanks produce hydrogen sulphide (H₂S) and methane. H₂S at concentrations of 100 ppm and above is immediately dangerous to life. Only licensed contractors with gas detection equipment should work at open tank access points.
NSW legal obligations: reporting requirements
Under the NSW Protection of the Environment Operations Act 1997 (POEO Act), any overflow of sewage that causes or is likely to cause a serious or material harm to the environment must be reported to the EPA immediately.
For PMHC-regulated OSSM systems, any overflow that has or may have reached:
- A watercourse (creek, river, drainage line)
- A stormwater system
- A neighbouring property
- A public area
must be notified to PMHC’s environmental health team. Do this as soon as practical, the notification obligation is real, and late or absent reporting can worsen your legal exposure.
In the Hastings River catchment, any overflow reaching a waterway is treated seriously because of the sensitivity of the estuary system and the downstream effects on water quality.
Cleaning up after a septic overflow
If overflow has occurred on your property:
Surface contamination:
- Restrict access to the contaminated area until clean-up is complete
- If on hard surfaces: carefully shovel and bag any solid material; do not hose to drains
- Apply a disinfectant (diluted bleach at 1 part bleach to 9 parts water) to hard surfaces after solid removal
- Allow to air dry
Soil contamination:
- Soil contaminated with sewage should be removed to a disposal depth of at least 150 mm in affected areas
- Removed soil must be disposed of as liquid waste at a licensed facility
- Fresh soil replaces the removed material
- Mark the affected area and avoid use for edible garden purposes for at least 12 months
Grass and garden:
- Contaminated grass should be left for several weeks of sun exposure to allow natural pathogen die-off
- Avoid the area for recreation, particularly for children, during this period
Internal backup cleanup:
- Sewage that has backed up into the house requires professional biohazard cleaning
- Standard household cleaning products are not adequate for sewage-contaminated surfaces
- Remove and dispose of any porous materials (carpets, upholstery, timbers) that have been directly contaminated
After the emergency: finding and fixing the cause
An emergency pump-out stabilises the situation, it doesn’t fix the underlying cause. After the overflow is resolved:
- Schedule a full septic inspection to identify the root cause
- Get a written assessment of what failed and what’s required
- If the absorption area has failed, get PMHC OSSM approval for remediation before proceeding
- Review pump-out frequency to prevent recurrence
A sudden surge in guest numbers, Christmas, New Year, school holidays, is one of the more common triggers behind an overload-driven overflow. Our guide on preparing your septic for holiday guest peaks covers how to head this off before a big household arrives, rather than dealing with it as an emergency mid-stay. An east coast low or other major rain event is the other common trigger, our septic triage guide for after big rain sets out a check-in-order routine for exactly that situation. Storm events also bring power outages that stop an AWTS treating properly until power is restored; see our guide on AWTS power outages for what to check once the system is back online. Heavier winter kitchen grease loads are a less obvious but genuine contributing factor too; our guide on winter grease loads and why kitchens block trenches in July explains why an already-saturated wet-season system has less margin to absorb the extra fat a lot of households send down the drain in the colder months. Bushfire damage to above-ground tank components, vent lines or an AWTS control panel is a less common but genuine trigger too; our guide on protecting poly tanks and vent lines during bushfire season covers what to check before and after a fire event.
FAQs
Is sewage overflow dangerous to breathe?
At close range, sewage overflow produces unpleasant odours from hydrogen sulphide and organic decomposition. At normal outdoor distances, the odour is unpleasant but not at concentrations dangerous to breathe. The primary health risk is from direct contact and ingestion, not inhalation. However, never enter a confined space near an active septic overflow.
How long do pathogens survive in soil after a septic overflow?
Most faecal bacteria (E. coli, Salmonella) survive 1-3 weeks in warm, moist soil; longer in cold, wet conditions. Viruses (norovirus) and protozoa (Cryptosporidium oocysts) can survive weeks to months. The conservative approach is to treat contaminated soil as a hazard for at least 6-12 weeks after an overflow event.
Can I use my bore water after a septic overflow near it?
Do not use bore water for drinking until you have tested it. Request an immediate E. coli and coliform test from a NATA-accredited laboratory. Results are typically returned within 48 hours. Until results are available, boil water or use alternative supply for drinking and food preparation.
What’s the cost of emergency pump-out in the Hastings region?
Emergency pump-out services (same-day or after-hours) typically cost $400 to $800+ depending on tank size, travel distance, and time of day. Remote hinterland properties (Comboyne, upper Wauchope) may attract travel surcharges. This is significantly more than a scheduled pump-out, another reason preventive maintenance pays for itself.