Septic tank decommissioning

When a developed property is connected to sewer, any onsite effluent disposal systems such as septic tank and leach drain/soakwell systems will eventually require decommissioning.  The Health (Miscellaneous Provisions) Act 1911 require disused septic tank and other wastewater systems to be decommissioned where a premises is connected to sewer and under the following circumstances:

  • When there is a change in the use of the premises, decommissioning must occur within 60 days.
  • When there is a change of ownership of a property, decommissioning must occur within 60 days following that change of ownership
  • If foundations for a building on the premises are to be built closer than 1.2 metres to the apparatus, or if a building is to be constructed above the apparatus, decommissioning must occur before building works commence


Decommissioning means that the contents of the tank are pumped out and the system is either removed or back-filled. The contractor is required to pump out the entire contents of the tanks in accordance with the provisions of the
Environmental Protection Act 1986, and dispose of the waste at an approved facility. If the system can’t be removed, the tanks should still be pumped out, the bottom of the tanks broken up and the system back-filled with sand. Septic tanks which have not been decommissioned should not be paved or built over without approval from the Town.

Due to the costs involved in both decommissioning a septic tank and connecting to sewer, householders are not automatically required to decommission tanks when they connect to the sewer.

Disused septic tank systems can be converted into the primary treatment tank for a greywater system. However, the existing drainage receptacle (e.g. soak wells or leach drains) must be replaced with an approved greywater system.