- Last updated:
- 09 May 2019
Properties not connected to public sewerage need to have an on-site sewerage facility (OSF).
On-site sewerage facilities
An OSF is any system that stores, treats and disposes of household wastewater on the property. They consist of two components; the treatment plant and the land application area. For a more comprehensive guide refer to council's what is an OSF fact sheet.
All systems need approval from council before installation. Once approved, the property owner will receive a copy of the approved plan. Then a licensed drainage contractor can proceed to install the facility. It is the responsibility of the contractor to:
- install the facility correctly
- ensure completion of inspections and certifications.
Types of systems include:
- septic tanks
- activated sludge
- aerated wastewater treatment
- split black and grey water treatment
- holding tank with pump out
- composting i.e. wet or waterless
- recirculating sand filter.
Factors to consider when choosing a system include:
- soil type of the property
- size and slope of the property
- quantity of water to be treated
- amount of water available
- proximity to waterways
- spread of load throughout the day
- initial cost of system and land application area
- ongoing maintenance requirements
Before selecting an OSF, a licensed site and soil assessor must visit the property. They will recommend the level of treatment required for your wastewater. Sewerage treatment can involve up to three stages:
- primary treatment: breaks down solid material to liquid waste, then disperse below ground
- secondary treatment: breaks down organic material to wastewater suitable for surface or subsurface irrigation
- advanced secondary treatment: reduces suspended solids to wastewater suitable for release into sensitive ecosystems.
The land application area is where the treated wastewater is disposed of within the property boundary. Using a land application area, avoids causing harm to:
- occupants of the property
- neighbouring properties, and
- the surrounding environment, including waterways.
There are three types of land application areas:
- trench based systems - transpiration to large flat areas with absorbent soils
- surface irrigation systems - disperses using sprinklers, may not be suitable for sloping land
- sub surface systems - disperses using pipes beneath a layer of suspended soil.
OSFs need regular maintenance to ensure they operate in a safe and effective manner. Poorly maintained and malfunctioning systems can impact public health, the environment and resale value.
- make sure the system is well maintained and works properly. You may need a service agent agreement. Depending on the system, servicing frequency can vary from quarterly to yearly
- take reasonable steps to keep all plumbing and drainage on the property in good condition
- ensure the system does not create a nuisance or pose a health risk to the surrounding area.
Servicing may include:
- measure sludge and scum levels
- ensure adequate chlorine supplies
- ensure pumps and blowers are operational
- clean filters
- test chemical levels
- check for evidence of bacteria die-off
- check for ponding of wastewater in the land application area
- check mechanical components
- ensure plant is in operational condition.
Besides regular servicing, property owners can ensure the safe operation by performing extra actions. These include:
- avoiding anti-bacterial products and using only septic safe products
- prevent ponding of wastewater in the land application area to avoid spread of sickness
- be alert to any failure of the electrical components of the system
- take note of any leaking water or broken pipes
- act on any change in odour coming from the plant
- listen for the correct operation of the system.
OSFs, including septic tanks must be correctly decommissioned. This is to ensure the tank isn't a future risk to public health or the environment.
Approved liquid waste contractors must:
- remove all effluent and sludge
- disinfect and neutralise the tank.
The tank then needs to be buried to meet council guidelines.
For more information refer to council's septic tank decommissioning procedure fact sheet.
To apply for a permit to install or change an OSF:
- form 1A application form
- site and soil report with details of the proposed system design
- installation and minor alterations certification form
- compliance and commissioning certification form.
OSF eServices is an online reporting facility that allows real time submission of service reports via an app on your service agent's:
- smart phone, or
Service reports provide important information on the performance and maintenance requirements for OSF. Services reports also provide a means of monitoring OSF discharges to ensure that OSF do not pose a risk to the:
- environment, or
- health of the community.
This service will ensure that service reports are effective and improve communication between:
- homeowners, and
- OSF service agents.
Council offers several ways to submit your service report:
- by the OSF eServices app
- integrating your business system with council's system
- by email or post
- in person at any of council's development counters.
To register to use the app or integrate your system, complete the:
For more information, refer to:
Contamination of waterways should be reported to council immediately.
Reports of odour problems are also investigated as odours can show system failure.
For more information refer to council's OSF responsibilities and complaints fact sheet.
To report a problem contact council's development services.
Further details are available for:
- common failings of OSFs
- water conservation
- catchment water quality improvement program - OSF management.