On-site Sewage Management Systems

The term on-site sewage management system refers to any system that processes wastewater and disposes of the effluent within the premises.


The main types of on-site sewage management systems in The Hills Shire are septic tanks and aerated wastewater treatment systems.

Step 1.Septic Tanks

A septic tank is a waterproof tank usually located below ground level. It provides treatment of sewage by allowing solids to settle to the bottom of the tank. Oils and fats float to the top to form a scum layer.

Anaerobic (in the absence of air) bacterial digestion of the stored solids produces a sludge which accumulates at the bottom of the tank.

The partly treated effluent flows from the septic tank to either a holding tank for regular pump out or to a soil absorption system.


Step 2.Aerated Wastewater Treatment Systems

Aerated wastewater treatment systems (AWTS) use aeration of wastewater. This is an integral part of the treatment process.

A typical AWTS treats wastewater through the following process:

  • Settling of solids and flotation of scum in an anaerobic primary chamber (septic tank)
  • Oxidation and consumption of organic matter through aerobic biological processes
  • Clarification - secondary settling of solids
  • Disinfection using chlorine or other approved means if surface land application of treated wastewater is to occur
  • Regular removal of sludge to maintain the process

A list of accredited systems are located on the NSW Health website.


Step 3.Other Systems 

Council will also consider alternative sewage treatment systems providing they are:

  • accredited by NSW Health or
  • meet the required standards

Approval to Install

Approval to Install

To install a new on-site sewage management system on your property you must gain approval from Council.

You must submit an application together with all the required information and an application fee.

The policy below also relates to the installation of on-site sewage management systems in flood plains.

Please note: Application fees are variable depending on the size of the system. Please see Council’s Fees and Charges document for the current fee structure (Part 5 of Council's Hills Shire Plan).

Local Approvals Policy - 2021-2024(PDF, 1MB)

Application for Approval to Install / Amend a System of Sewage Management(PDF, 579KB)

Approval to Operate

Step 1.Approval to Operate Information

Approval is required to operate a system of sewage management under:

Subdivision 6 of the Local Government (General) Regulation 2021. 

Council must issue an approval to operate for every existing on-site sewage management system in The Hills.

Currently there are around 3500 on-site sewage management systems on Council's register. There are a large number of properties that have not submitted an application for approval regardless of when the system was installed.


Step 2.Application for Approval

If you have an on-site sewage management system and have not submitted an application for approval to operate you to:


Step 3.New Owners who have recently bought a property that uses an On-site Sewage Management System

The Local Government (Gen) Regulation 2005 provides a period of three (3) months in which to make an Application for an Approval to Operate.

A twelve (12) month exemption period may apply to new owners in certain circumstances. Please refer to Appendix 3 of Council's Local Approvals Policy - 2021-2024(PDF, 1MB)

For further information email council@thehills.nsw.gov.au or contact Council's Health and Environment Protection Division on +61 2 9843 0555.