Approved primary treatment systems

The Health (Treatment of Sewage and Disposal of Effluent and Liquid Waste) Regulation 1974 requires all Primary Treatment Systems (PTSs) (also known as Septic Tanks) to be approved by the Chief Health Officer.

The department now requires all manufacturers’ to comply with the Code of Practice for Product Approval of Onsite Wastewater Systems which requires all PTSs to be certified to AS/NZS 1546.1. This will ensure that the quality standards of all PTSs manufactured in WA are in line with the Australian Standards.

Please be aware that the minimum capacity of a PTS treating all wastes connected to a residential premises up to 5 bedrooms is 3180L. A single tank can be approved for residential installation only when it is fitted with a baffle as an approved product and has a capacity equal to or larger than 3180L.

A primary treatment system with a single baffled tank with a capacity less than 3180L can be approved for small commercial installations only when the wastewater volume combined with the 1820L reserve is less than the total system capacity and an engineering certificate is provided to confirm the integrity of the configuration.

The following tables detail the specifications of precast concrete septic tanks (Table 1) and non-concrete septic tanks (Table 2) approved for use in Western Australia.

Table 1: Approved precast concrete septic tanks

Table 2: Approved non-concrete septic tanks

For more detailed information on approval process for sewage holding tanks, please refer to Guidance for the use of sewage holding tanks associated with temporary ablution blocks.

More information

Environmental Health Directorate
Department of Health
Telephone: 9222 2000
Email: ehinfo@health.wa.gov.au