Sewerage / Sheet 4
Septic tanks and other on-site systems
A home with no sewer connection treats its own sewage in an on-site system, such as a septic tank, and in Victoria the owner is responsible for keeping it working: a council permit is needed to install or change one, and the law requires owners to stop it overflowing and to tell the council when it fails.
General information. The rules here are Victoria’s, from EPA Victoria, with Western Australia’s service intervals for comparison. Your council administers the rules where you live.
What counts as an on-site system
EPA Victoria calls them onsite wastewater management systems, or OWMS. Most of Victoria’s sewage goes through the sewerage network, but some areas, rural ones among them, have no sewer connection, and there an OWMS treats the sewage so it can be reused or dispersed. A septic tank system is one kind.
For a system handling up to 5,000 litres a day, the permit to build, install or alter it comes from the local council, and the application includes a certificate of conformity for the system. Altering means changing its design, how it runs, or the use of the premises, such as a house becoming a business; routine maintenance does not count.
EPA Victoria’s concern is what a poorly installed or maintained system can release, especially an older one: untreated sewage that can contaminate drinking water, land or waterways, or simply smell.
An owner’s duties in Victoria
The Environment Protection Regulations 2021 apply to every system, including older ones installed without a permit, and councils enforce them. In EPA Victoria’s summary, the owner or occupier must:
- take reasonable steps to keep the system running without risk to people or the environment;
- make sure it does not overflow;
- tell the council if the system poses a risk or has a problem;
- keep it in good working order (a duty that does not fall on residential renters).
Owners must also:
- give whoever manages the system, a renter for example, written information on how to use it;
- keep maintenance records and show them to the council on request.
When a tank is pumped out, the contents count as priority waste, and reasonable steps must be taken to see it goes somewhere lawfully able to receive it.
How often systems are serviced
EPA Victoria says how often a tank needs de-sludging depends on how much it is used and on the manufacturer’s requirements. WA’s Department of Health gives general service periods, while reminding owners to follow their approval conditions and the manufacturer’s advice first.
| System | General service period |
|---|---|
| Aerobic treatment unit | Every 3 months |
| Septic tank and leach drains | Every 2 to 3 years |
EPA Victoria gives a licensed plumber or an accredited servicing agent as examples of professionals who can check whether the system needs cleaning, de-sludge it, fit an alarm that warns of breakdowns, and check or repair its pipes and tanks.
Keeping the bacteria working
Some of the microorganisms in a system are doing the treating, and the tank depends on them. EPA Victoria’s advice, condensed:
- Scrape plates before washing so fat and grease stay out, and keep solids, sanitary napkins and tissues out of the system.
- Skip a food waste disposal unit unless the system is built for the extra load.
- Choose biodegradable soaps and detergents low in phosphates and salt, and use only as much as needed.
- Avoid strong bleaches, whiteners, nappy soakers, spot removers and disinfectants, and never pour paint or chemicals down the drain.
- Spread the water out: not all the washing in one day, not the dishwasher and washing machine together.
- Keep cars off every part of the system, keep stormwater out of it and away from the disposal field, and do not cover the tank or field.
Signs a system is failing
EPA Victoria’s warning signs, worth watching most closely on older systems:
- the absorption field turning wet, with wastewater pooling on top
- wastewater running off the disposal area
- a smell of effluent near the system
- slow drains or toilets
- a full or blocked grease trap
In Victoria the owner or occupier has to report any sign of failure to the council and explain what has been done or is planned to fix it. If someone else reports it first, a smell for instance, a penalty may apply.
Overflows, and looking inside a tank
WA’s Department of Health notes that sewage spills happen on properties with septic tanks and leach drains as well as on sewered ones. Its precautions for a spill:
- Keep anyone without protective gear, and animals, away until the area has been cleaned and disinfected.
- Anyone cleaning up wears rubber boots, rubber gloves and washable or disposable overalls, with cuts and scratches covered by waterproof dressings first. Wash and disinfect straight away any wound that wastewater touches.
- Treat everything the wastewater touched as contaminated, wash hands with soap and warm water before eating, and wash dirty clothes on their own.
- See a doctor straight away if anyone becomes ill.
Inside the tank is another matter. Safe Work Australia’s list of confined spaces includes tanks, pits and underground sewers: places not built for people, where the air may be short of oxygen or carry gases. Under its rules a person has entered once their head or upper body is inside. Its duties are written for workplaces, and they call for an entry permit, a risk assessment, a standby person outside and rescue procedures before a worker goes in. EPA Victoria gives a licensed plumber or accredited servicing agent as examples of professionals who can de-sludge and check a system.
After a fire or a flood, EPA Victoria’s advice is to have a licensed plumber or service technician assess the system.
Decommissioning an old system
In most of Victoria, a septic system that is no longer needed, for instance because the property has been connected to the sewer, has to be decommissioned: emptied, cleaned out and made unusable. Old systems left in place can contaminate groundwater, and ground that has already taken leaked waste can stay contaminated afterwards.