On-site sewage facilities

An on-site sewage facility is any system that stores, treats and disposes of household wastewater on the property. Poorly sited or maintained on-site sewage facilities can impact public health and the environment. The owner of the facility is responsible for ensuring the system is maintained and functioning properly.

It is an offence under the Plumbing and Drainage Act 2018 to use plumbing or drainage that is the result of permit work, unless an inspection certificate or final inspection certificate has been issued stating the work is compliant, operational and fit for use.

The disposal of effluent (treated sewage) may occur:

  • on the property on a designated area (called a land application area)
  • off the premises by collection from a holding tank by a council-approved liquid waste carrier.

Systems over 20 EP (equivalent persons), would also require approval and further monitoring from the Environmental Protection Agency.

Types of on-site sewage systems

The Department of Housing and Public Works grants approval to treatment plants that produce:

Further information is available on the Department of Housing and Public Works website.

Local government approves the installation of on-site sewage facilities.

Treatment systems for household wastewater include:

  • conventional domestic sewage treatment plants (secondary treatment or better)
    • activated sludge system
    • biological trickling filter system
    • extended aeration system
    • aerated/aerobic sand filter system
  • conventional domestic sewerage treatment facilities (secondary treatment or better)
    • advanced passive treatment system (or other similar systems)
  • septic tanks (primary treatment)
    • all-waste septic tank (all household wastewater)
    • black water septic tank (toilet, urinal and bidet wastewater only)
    • greywater septic tank (sullage wastewater only)
  • composting systems
    • dry vault system (toilet waste only – waterless)
    • wet system (all household wastewater – may be considered a domestic sewage treatment plant)
  • holding tanks
    • off the premises by collection from a holding tank by a council-approved liquid waste carrier.

Sewage treatment facilities register

Local government maintains a register of such treatment plants and requires maintenance reports to be submitted to council as per the requirement under the Treatment Plant Approval determined by the Department of Housing and Public Works. If local government does not receive a service report when your service is due, a letter may be sent requesting a copy of the report. If a report is not provided, further action will be taken by the local government.

Septic tanks

It is recommended that septic tanks be pumped out every five years by a professional pumping contractor.

Land application areas

A land application area is the designated area on a property for application of the treated effluent and includes:

  • irrigation system
    • surface irrigation (spray above ground)
    • sub-surface irrigation (drippers in shallow trench – large surface area)
    • covered surface irrigation (drippers on natural ground covered by mulch, woodchip, etc – large surface area).
  • evapotranspiration-absorption trench/bed/mound
    • trench or bed (embodies the principles of evaporation, transpiration and absorption)
    • elevated sand mound (specially constructed on natural ground level).

The type of land application area will depend on the level of treatment the wastewater has received prior to disposal.


Related information

Onsite sewerage systems - care and maintenance helpful hints 32KB