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City of Bunbury


In areas where reticulated sewer is not available, on-site disposal of waste water is required. Application should be made through the City to install an onsite wastewater treatment and disposal system. These also include mechanical equipment wash down bays that discharge wastewater on site. Refer to the information note for further guidance

The City can approve systems for single residential developments and industrial/ commercial developments producing not more than 540 litres of waste water per day. Larger developments require approval by the Department of Health (WA). Please refer to the application form for further details regarding the application process and information to be included.

The type and size of system will depend on a number of factors including:

  • Volume of wastewater produced
  • Type of soil
  • Proximity to water bodies
  • Depth to groundwater

Contact the Water Corporation on 13 13 95 to determine whether deep sewer is available to your property.

Contact a licensed plumber to ascertain the most appropriate effluent system for your property.

Wastewater system decommissioning

Once a sewer connection is available to a property, it must be connected within five years of the Water Corporation advising of its availability. If the property is sold, it has to be connected within one year of the settlement date. Wastewater systems must be ‘decommissioned’ to prevent them from collapsing in the future and possibly causing damage or injury.

When do I have to decommission a septic tank?

The City strongly recommends that onsite effluent disposal systems be decommissioned as soon as possible after a property is connected to mains sewer. Under law, systems must be decommissioned:

  • If there is a material change in the use of the premises – not more than 60 days after the day on which the change in use occurred. An example of this is if a premises changes from a private residence to a childcare centre.
  • Not more than 60 days after every person who was an owner of the premises at the time the premises was connected to the sewer ceases to be an owner of the premises.
  • Before building work commences if foundations for a building on the premises are to be built closer than 1.2 metres from the apparatus or a building is to be constructed above the apparatus.

How do I decommission my old septic system?

  • Any remaining wastewater in the system is pumped out and taken away by an approved liquid waste contractor
  • Wastewater or greywater systems are removed
  • Where removal of the system is not practicable, the base of the tanks must be broken up and the entire system backfilled with clean fill.