Septic Tanks

What Are On-Site Sewerage Facilities?

On-site sewerage facilities are used for the treatment of domestic sewage on premises in unsewered areas.

An on-site sewerage facility is a facility on a premises for treating, storing and disposing of sewage generated on the premises. An on-site sewerage facility may include:

• an on-site sewage treatment plant, which uses mechanical, biological and filtration methods to treat waste before discharging through either above or below ground irrigation systems; or
• a septic system, which uses biological methods to treat waste before discharging through a below ground system.

Local Government Approvals

Where an on-site sewerage facility is to be installed, a plumbing application must be made to the local government.

The requirements for an on-site sewerage facility are provided under the Plumbing and Drainage Act 2003 (PDA), the Queensland Plumbing and Wastewater Code (QPW Code) and its referenced Australian Standards, these being:

• AS/NZS 1546.1:1998—On-site domestic wastewater treatment units—Septic tanks
• AS/NZS 1546.3:2001—On-site domestic wastewater treatment units—Aerated wastewater treatment systems, and
• AS/NZS 1547:2000—On-site domestic wastewater management.

An application for an on-site sewerage facility must be assessed by the local government in accordance with the QPW Code (Parts 1 and 3), which includes the siting of the facility and layout of the land application area. In assessing a plumbing application for an on-site sewerage facility, the local government may also attach conditions to its approval. For example, this could include:

• the method of disposal for the treated effluent (above or below ground),
• the design of the land application area on the property where the wastewater is to be disposed based on the relevant soil type and its potential impact on surface and groundwater, and proximity to neighbouring properties and any sensitive environmental areas.

Chief Executive Approvals

In addition to the local government’s approval, under the PDA a treatment plant must also have a chief executive approval issued by the Department of Housing and Public Works (department) before it can be installed. Generally, the chief executive approval is obtained by the manufacturer of each treatment plant model. The following types of treatment plants currently require a chief executive approval:

• secondary
• advance secondary, and
• advanced secondary with nutrient removal.

 A chief executive approval is required for treatment plants designed to treat sewage for less than 21 equivalent persons. For treatment plants designed to service 21 or more equivalent persons approval must be obtained from the Department of Environment and Heritage Protection prior to installation.

 A chief executive approval is not required for:

• a septic tank
• the method of disposal for the treated effluent

the land application area, and

• chemical, composting or incinerating toilet or a dry-vault (waterless) toilet.

 The department assesses the treatment plant’s performance. To receive a chief executive approval, the manufacturer must undertake testing with an accredited testing agency and present the results to the department to demonstrate that the treatment plant meets the minimum water quality criteria specified under the QPW Code. A list of approved treatment plants is available on the department’s website via the link On-site sewerage facilities. Local governments are advised to use this approved list for guidance when assessing a plumbing permit for an on-site sewerage facility that includes a treatment plant.

Resources

More information can be found here: Septic Tanks.

Download a Septic Tank Factsheet