Gravity Sewer Systems

A reticulated Community Wastewater Management System (CWMS) provides for the collection and carriage of septic tank effluent or sewerage by either gravity flow or by pumping (either positive, or negative pressure (vacuum)) to a treatment facility that is owned, operated and maintained by the local Council, or another agency.

Currently in SA the most common reticulated CWMS is a STEDS (Septic Tank Effluent Disposal Scheme). These schemes comprise a gravity collection system and generally provide a connection to each property at a depth to allow connection of the property wastewater system by gravity and may receive the discharge from a septic tank and/or a greywater treatment tank or other approved treatment process on the property.

The Alexandrina Council’s primary sewer network is a gravity sewer system whereby sewage collection from the dwelling is connected via a septic tank to the greater gravity network, or connected directly (without septic tank, if a full sewer network), to the greater gravity network. The greater network then flows via gravity to electric sewer pump stations which then pump sewerage to a wastewater treatment plant for processing.

Using a gravity sewer system on a property, or to service a property, is subject to approval by Council.

The developer (or representative consultant) is required to provide sufficient information to enable a proper assessment to be undertaken.

If approved, the Water Services Association of Australia (WSAA) Gravity Sewerage Code of Australia (WSA 02-2014) is used as the basis for design and construction of a gravity sewer system.

The WSA 02-2014 Code together with relevant Codes, Council Standards, Typical Drawings, Authorised Products, Materials & Suppliers documents and other information cover the more detailed requirements and provide ‘deemed to comply’ solutions.

Reference Documents

The following Codes & Criteria also apply to any CWMS design undertaken;

• Alexandrina Wastewater - Typical Drawings
• WSA 01 – Polyethylene Pipeline Code of Australia
• WSA 02 – Sewerage Code of Australia
• WSA 04 – Sewerage Pumping Station Code of Australia
• WSA 06 – Vacuum Sewerage Code of Australia
• WSA 07 – Pressure Sewerage Code of Australia
• WSA 302 – SCADA Guidelines
• Community Wastewater Management Systems Code, April 2013 (SA Health)
• Code for Establishing & Applying Property Units as a Factor for the Imposition of Annual Service Charge for Community Wastewater Management Systems, 20 April 2006
• South Australian Community Wastewater Management (CWMS) Design Criteria, July 2019
• SA Water – Technical Standard TS-502 Authorised Products Gravity Sewer and Pressure Pumping Main Systems, Version 5.0, 25 June 2020 or a subsequent revision; with exception to those items documented

For more information in relation to Wastewater Services or Stormwater Reuse, please contact cwms@alexandrina.sa.gov.au