Legislation
When a developed property is connected to sewer, usually under the infill sewerage program, any onsite effluent disposal systems such as septic tank and leach drain/soakwell systems will eventually require decommissioning.
This means that the contents of the tank are pumped out (by an approved contractor) and the system is either removed or backfilled.
If the system can’t be removed, the tanks should still be pumped out and the bottom of the tanks can be broken up and the system backfilled with sand.
As there are 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.
However under the Health (Treatment of Sewage and Disposal of Effluent and Liquid Waste) Regulations 1974 (PDF 0.99MB) (External site), decommissioning is required when
- The property is sold
- The use of the development changes eg from a residence to a child care centre
- Building extensions may encroach on minimums setback requirements from the system.
Septic tanks which have not been decommissioned should not be paved or built over without approval from the relevant local government.
Under the Code of Practice for the Reuse of Greywater in Western Australia (PDF 581KB) , disused septic tank systems can be converted into the primary treatment tank for a greywater system. However, the existing drainage receptacle (e.g. soakwells or leach drains) must be replaced with an approved greywater system.
For further information, contact the Environmental Health Directorate on +61 8 9388 4999.
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