Decommissioning existing systems


When sewer becomes available to a premises which has an onsite effluent disposal system, the owner has five years in which to disconnect the disposal system and connect to the sewer.  When undertaking this work many people take the opportunity to decommission the onsite disposal system at the same time although this is not legally required.

Decommissioning of an onsite effluent disposal system is only required when –

  • There is a change in use of the premises, or 
  • The property is sold (within 60 days after change of ownership), or 
  • Extensions to the property encroach on set-back requirements for the system.

To decommission an apparatus you must –

  • Have the septic tanks emptied by a Licensed Liquid Waste Contractor and disposed of at an approved site. 

and either

  • Remove the septic tanks, leach drains or soak wells from site and backfill with clean compacted sand (this option is recommended particularly if property development is planned in the future).


  • Remove the septic tank, leach drain or soakwell lids and ensure the bottom of the septic tanks are broken up. Backfill the septic tanks, leach drains and soak wells with clean compacted sand.

Unfortunately once a system has been decommissioned it can be difficult to prove this fact. Therefore owners are encouraged to retain copies of any receipts and where possible take photos of the decommissioning work being undertaken for future reference.