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Sewage management onsite

If you live in a house that is not connected to the main sewer, then chances are your yard contains an on-site sewage management system. If this is the case then you have a special responsibility to ensure that your system is working well. Such on-site sewage management systems include septic tanks, aerated wastewater treatment systems (AWTS), pump out systems, composting toilets, effluent soak-away trenches, mounds and irrigation areas, greywater application systems and domestic grease traps.  

Chapter G8 "Onsite Sewage Management" of Shoalhaven Development Control Plan 2014 specifies development guidelines for wastewater treatment. View this document in the planning register.

What is an on-site sewage management system?
Types of on-site sewage management systems
System operation and maintenance
Approvals and regulations
Contact us

What is an on-site sewage management system?

A domestic on-site sewage management system is made up of various components to complete two main processes:

  1. The storage and treatment of wastewater from a house to a certain standard; and
  2. Its application to a dedicated area of land.

Wastewater may be black water from the toilet and kitchen sink or greywater from showers, basins, and washing machines, or a combination of both. Wastewater, no matter where it comes from, can transmit disease and cause major environmental damage. Therefore, it should not be applied to land without treatment.

Larger on-site sewage management systems are generally called package plants. These systems are designed to treat wastewater from a larger development such as tourist cabins, caravan parks and conference centres.

Within the Shoalhaven there are more than 7,000 on-site sewage management systems.

Types of on-site sewage management systems

Septic tank
Septic tanks treat both greywater and black water, but they provide only limited treatment through the settling of solids and the flotation of fats and greases. Bacteria in the tank break down the solids over a period of time. Wastewater that has been treated in a septic tank can only be applied to land through a covered soil absorption system, as the effluent is still too contaminated for above ground or near surface irrigation. This system relies on the soil completing the treatment process as the effluent moves through the strata. However, not all soils are suitable for absorption trenches, and may result in effluent reaching the surface and/or groundwater and adversely affect receiving water bodies.

The aerated wastewater treatment system (AWTS) is an alternative to the conventional septic system. This effluent is treated to a level known as tertiary treatment with the effluent undergoing disinfection by chlorination or ultra violet light to remove bacteria and other microorganisms. The effluent produced may be surface or subsurface irrigated in a dedicated area.

The effluent contains fewer potential harmful pathogens because it is treated to a higher standard than the conventional septic tank. However, if the effluent is not appropriately disposed of, unacceptable levels of pollution will still enter the receiving environment.

The higher level of treatment achieved in an AWTS is conditional upon the system receiving regular maintenance. Without regular maintenance by a suitable qualified person, significant public health and pollution problems could eventuate.

Composting toilets
Composting toilets collect and treat toilet waste only. In these systems, toilet wastes pass from the pan down a chute and into a chamber. All faecal matter and other compostable matter produced in the dwelling, such as toilet paper, may be disposed of to this system where it is broken down into compost by natural decomposer organisms. When fully broken down, the compost may be used in gardens but must be buried and covered. Water from the shower, sinks and the washing machine needs to be treated separately, for example in a septic tank or AWTS as above.

Greywater treatment systems
Greywater treatment systems collect, store, treat and sometimes disinfect greywater to enable treated greywater to be used in toilets, washing machines and on gardens and lawns. Further information on Greywater is available.

Greywater diversion devices
Greywater diversion devices redirect greywater to the garden or lawn via a subsurface irrigation system. There are two types of greywater diversion devices (GDD):



  1. Gravity diversion device - A gravity diversion device incorporates a hand activated valve, switch or tap and is fitted to the outlet of the waste pipe of the plumbing fixture such as a laundry tub.  Greywater is diverted directly to a sub-surface irrigation system in the garden.
  2. Pump diversion device - A pump diversion device incorporates a surge tank to cope with sudden influxes of greywater for distribution of the greywater directly to a sub-surface irrigation system in the garden.  The surge tank does not operate as a storage tank.

Other alternative systems
There are many other types of on-site sewage management systems such as sand filter beds, wetlands, and mounds. New products are continuing to be developed and come on to the market. Council or the NSW Department of Health have more information on these systems if you need it.

Partial on-site systems e.g. pump out and common effluent systems (CES) also exist. These usually involve the preliminary on-site treatment of wastewater in a septic tank, followed by collection and transport of the treated wastewater to an off-site facility. Pump out systems use road tankers to transport the effluent, and CES use a network of small diameter pipes. The assessment may indicate that the proposal would be better served by a package treatment plant utilising the land suitable for effluent disposal, with the plant and disposal field being managed for all future owners of the development.

Regardless of the type of system, you should try to avoid contact with all treated and untreated wastewater and thoroughly wash affected areas if contact does occur.

System operation and maintenance

Sewage management systems that have not been well maintained may release dangerous levels of sewage pollution to the environment. Sewage pollution causes contamination of water, which can spread disease and lead to environmental degradation. The cumulative impact of effluent can create a critical problem.

Fines may be imposed under the Protection of the Environment Operations Act, 1997 and the Local Government Act, 1997 if wastewater is not managed properly.

What you put down your drains and toilets has a lot to do with how well your system performs. Maintenance of your sewage management system also needs to be done well and on-time.

The following brochures provide a guide to the types of things you should and shouldn't do with your system. They also provide information on your system and a few warning signs that signal to you that there are troubles with your system. Please ensure that these problems are attended to immediately to protect your health and the environment.

Managing Wastewater in your Backyard (PDF 91kb)
Your Septic System (PDF 151kb)
Your Aerated Wastewater Treatment System (PDF 104kb)
Your Land Application Area (PDF 123kb)
Your Waterless Composting Toilet (PDF 115kb)

To have your septic tank or AWTS desludged, please download the Septic Tank Clean Out Application Form . This includes details of costs which must be paid to Council before the service is carried out. 

Reducing water usage
Reducing water usage will lessen the likelihood of problems such as overloading with your septic system. Overloading may result in wastewater backing up into your house, contamination of your yard with improperly treated effluent, and effluent from your system contaminating groundwater or a nearby waterway. Your sewage management system is also unable to cope with large volumes of water such as several showers or loads of washing over a short period of time. You should try to ensure water use is spread more evenly throughout the day and week.
For further water reduction tips, please refer to Shoalhaven Water website (New Window).

Approvals and regulations

It is essential that on-site sewage systems be operated efficiently to maintain our local environment and public health.

An application is required to be submitted to Council for approval to install a system of sewage management. Download the Drainage Application form (PDF 151kb). Following an inspection of this system, Council will issue an Approval to Operate. Typically, this process occurs at the same time a new house is built.

Many systems, especially those installed prior to 1999, would not have had an Approval to Operate a System of Sewage Management issued following the original installation of the system. In this instance, an application is required to be made to Council. Download the Approval to Operate a System of Sewage Management application form (PDF 76kb). An application is also required to be made by a person who purchases (or otherwise acquires) land on which any sewage management facilities are installed or constructed.

Council has implemented an approvals and inspection regime aimed at achieving environmental and public health performance objectives, while minimising cost to the community.

All on-site sewage management systems are inspected by Council on a regular basis and your approval renewed. The frequency of inspections depends on the risk operating that system poses to public health and the environment. Council will send a letter to you when your renewal is due outlining the fees that apply to your system. For further information regarding your renewal, please download Council's information sheet Due for Renewal or information on Fees and Charges  is also available.

Domestic greywater diversion may be carried out without the prior approval of Council if the conditions of Section 75A of the Local Government (General) Regulation 2005 are met. Greywater diversion devices redirect greywater to the garden or lawn via a subsurface irrigation system. You will need a plumber to install the device.

Further information

Contact - Environmental Services (Onsite Sewage Management Unit)

(02) 4429 3598 (Mon/Tues/Wed) for properties north of Sussex Inlet
(02) 4429 8941 (Mon/Wed/Thurs) for properties south of and including Sussex Inlet

To organise a pump out of your existing system, please contact Shoalhaven Water on (02) 4429 3343

Other Useful Links

Environment & health protection guidelines – onsite sewage management for single households 1998 (PDF 2.32mb)

Various greywater fact sheets (new window)

Laundry detergents – the salts, nitrogen and phosphorous content of various washing detergents available in Australia (new window)