On-site Wastewater Management Systems (OWMS)

Properties without a sewer system connection will require an OWMS to treat and then recycle or dispose of wastewater within property boundaries.

An OWMS is commonly referred to as septic or a septic tank system. There are a number of different types of OWMS available. To choose a system that is right for you and your property, you should liaise with a licenced plumber, and ensure that the system conforms to relevant Australian and New Zealand Standards.

Whichever system you choose, you may be required to conduct a Land Capability Assessment (LCA). In unsewered areas, a LCA should be undertaken for each site that requires the installation of an OWMS, unless Council is satisfied the site is low risk or sufficient information (e.g. soil permeability rates, soil types, depths to water table, fractured rock and other limiting factors) has already been gathered about the site. An LCA is mandatory for any allotment within a Special Water Supply Catchment Area. If you are unsure of whether an LCA is required, please contact Council’s Health Protection Unit on (03) 5232 9400 prior to submitting your application.

Applying to install or alter an OWMS permit

Prior to the installation or alteration of any OWMS, a permit must be obtained from Colac Otway Shire's Health Protection Unit. Please refer to the OWMS application form to understand the required documentation to accompany your application. A copy of the certificate of conformity for the system to be installed (if applicable) can be obtained from the relevant system manufacturer.

All OWMS works must comply with the permit issued by Colac Otway Shire, the Environment Protection Act 2017, the EPA Code of Practice for Onsite Wastewater Management and the relevant Australian/New Zealand Standards.

If your OWMS application is approved, the licenced plumber detailed on the permit must contact the Health Protection Unit to arrange an inspection of the system prior to backfilling. Seven days’ notice is preferred, prior to the commencement of works.   

When Council has received all the required documentation, a final inspection will be conducted by a Colac Otway Shire Environmental Health Officer.  If Council is satisfied that the permit conditions have been met, a Certificate to Use (CTU) the system will be issued.  The system cannot be used until a CTU is issued.  For new dwellings, a CTU must be issued before a Certificate of Occupancy can be issued by your Building Surveyor.

Amending, renewing or transferring an OWMS

If you need to amend, renew or transfer an OWMS, you must fill out the OWMS application form, and tick the appropriate category for the application.

What are Council’s responsibilities?

Council is responsible for approving OWMS with a flow rate of sewage not exceeding 5000 litres on any day. Systems that can treat more than 5000 litres per day require approval from the Environment Protection Authority (EPA).

OWMS have the potential for major environmental and human health risks, because of the pathogens and toxins they contain. Council has a commitment to administering and enforcing relevant OWMS legislation, and along with persons in control of an OWMS, a responsibility to minimise the impact of OWMS on public health and the environment.


Responsibility for managing and maintaining an OWMS falls with the property owner. An owner of land on which an OWMS operates must provide the occupier with written information regarding the correct operation and maintenance of the system. Persons in control of an OWMS must take all reasonably practicable steps to ensure the system is maintained in good working order and does not pose a risk to human health or the environment.

These steps include:

  • Regular desludging to remove the contents of the system, if applicable
  • Ensuring the integrity of pipes, tanks and storage systems.
  • Repairing and, when required, replacing all the components and fittings of the system.
  • Maintaining the biological and chemical processes integral to the proper functioning of the system.
  • Maintaining the integrity of the land used in connection with the system to ensure access to the system is not impeded.
  • Complying with the system manufacturer's specifications and recommendations.
  • Complying with any relevant council requirements.
  • Monitoring the system for signs of fail.

Persons in control of an OWMS must keep and hold all records of maintenance activities carried out on the system, including any pump-out and service records, for five years after each activity. These records must be made available for inspection upon request by Council.  

EPA Permits and Domestic Onsite Wastewater Management Responsibilities

Council is meeting its statutory responsibilities in relation to the assessment, permit and approval process for domestic onsite waste water systems.

Since November 2015, Council has issued 484 permits. Systems installed post 1 July 2016 upon approval would be assessed as EPA compliant.

A calendar year break down of permits is as follow:


















(to 9 August) 42.


A focus of the domestic wastewater management plan activities, is also the auditing and inspections of onsite domestic wastewater systems within declared water supply catchments.

Systems have been assessed and education to property owners and occupiers has been provided. 

Related Links:

Install an OWMS (Septic) System Application Form  

Information on suitable plants   

Plants-Suitable-for-Effluent-Fields.docx(DOCX, 58KB)

Help Protect our environment   

Septic_tank_tips_for_property_owners_and_holiday_makers.pdf(PDF, 197KB)

Your_septic_system_brochure.pdf(PDF, 1MB)

 Web-Final-Version-of-Operational-Plan-Domestic-Wastewater-Management-Plan-DWMP-20151113.pdf(PDF, 2MB)(PDF, 1MB)