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Septic tanks

Applications and Factsheets

Fact sheets

Most unsewered developments in Western Australia use septic tank systems to treat and dispose of sewage. These generally consist of two water tight tanks (or one large unit) and two sets of drainage receptacle e.g. leach drains or soak wells.

System installations are only permitted with local government or Department of Health approval (the Department of Health assesses larger development proposals). Persons wishing to install septic tank systems with leach drains/soakwells or an aerobic treatment unit (ATUs) need to lodge an Application to Construct or Install an Apparatus for the Treatment of Sewage (PDF 149KB) with the relevant local government.

This is to ensure that the system is of an approved design and manufacture, is properly sized and is suitably located.

It is an offence to install a wastewater system without an approval and it is also an offence to commission a system prior to a final inspection and approval to use from the local government.

Onsite treatment and disposal of effluent systems will not be approved if a property can be reasonably connected to sewer.
As they are designed to retain the solids in household wastewater, septic tank systems require routine maintenance. Pumping out the tanks on a regular basis stops accumulated fats and solids from overflowing into the drainage receptacles.

These soak wells or leach drains also need attention to ensure that the surrounding soil does not become over loaded. In systems that have been used for some time, the soil can begin to clog. Effluent is then less able to freely soak into the surrounding soil and begins to accumulate in the drainage receptacle. This can cause the effluent to surface around the drain/soak well and also back up into household pipes.

To improve the operation and longevity of drainage receptacles, new systems are now required to be alternating. This allows each section to be rested as effluent is diverted to the other leach drain or soak well area.
Persons wishing to manufacture septic tanks, leach drains and soakwells need to be familiar with the requirements of the Health (Treatment of Sewage and Disposal of Effluent and Liquid Waste) Regulations 1974 (PDF 0.99MB) (External site)

Manufacturers must apply to the Department of Health for product approval (Application for Product Approvals of Wastewater Disposal/reuse Systems) and to register their mark of distinguishing brand. Every article intended for use in the construction of an apparatus for the treatment of sewage is required to be legibly marked with the name of the manufacturer or this registered mark.
For further information, contact the Environmental Health Directorate on +618 9388 4999.

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