20 June 2016

Decommissioning disused wastewater systems

Under the Health (Treatment of Sewage and Disposal of Effluent and Liquid Waste) Regulations 1974, the owner of a property must decommission any disused apparatus for the treatment of sewage when a property is connected to the sewer.

This includes items such as disused septic tanks and aerobic treatment units.

When do I have to decommission my septic tank?

Decommissioning must occur:

  • 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 is a wastewater system decommissioned?

The steps involved in decommissioning a system include:

  • any remaining wastewater in the system is pumped out and taken away by an approved liquid waste contractor
  • septic tanks or aerobic treatment units 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.

Who can decommission a septic tank?

Only licensed and approved personnel can decommission septic tanks. A list of septic tank removal companies can be found in the Yellow Pages directory (external site).

Who is liable to pay for the cost incurred when there is change in property ownership?

Since the cost associated with decommissioning can be high, it is advisable for prospective purchasers of a property to determine if decommissioning has already occurred.

More information

Water Unit, Environmental Health Directorate
Department of Health
PO Box 8172
PERTH BUSINESS CENTRE WA 6849
Phone: 9222 2000 
Last reviewed: 20-06-2016
Produced by

Public Health