Servicing wastewater systems

The Department of Health is consulting on a draft code of practice for on-site wastewater disposal. The aim is to adopt the code of practice within future wastewater regulations to be created under the Public Health Act 2016. You are invited to provide feedback. Review the consultation page (external site) for more details. Submissions close 4.00 pm 28 September 2023. 

Without written permission from the local government, it is illegal to do the following:

  • Dismantle a wastewater system;
  • Emptying a wastewater systems;
  • Remove a wastewater system wholly or in any part; or
  • Alter or change the system’s mode of operation.

Primary Treatment Systems (Septic tanks)

Where installed, a primary treatment system needs to be pumped out every 4 years or more often according to the installation approval conditions. Pumping out of the primary treatment system must be done by a licensed contractor. Contact your local government Environmental Health Officer for further information.

Secondary Treatment Systems

Maintenance work on a Secondary Treatment Systems (STSs) can only be carried out by service persons authorised by the Chief Health Officer.  To obtain authorisation from the Chief Health Officer to service STSs, refer to the Becoming an authorised service technician for domestic on-site wastewater treatment systems document.

Maintenance, depending on the type of system, may include checking the blowers, contact media, pipework, valves, diffusers, effluent clarity and sludge return, removal of excess scum, testing the pump and general operation of the system. Where chlorine tablets are used, the amount supplied must be sufficient to last until the next scheduled service.

Service STSs after periods of non-use 

Many STSs will perform sufficiently under constant wastewater flow conditions but are not designed for sharp decreases or sudden shock loads. Wastewater flow variations can upset the system and set the system ‘off track’ and it could take some time for the system to return to normal.

Many systems also have slow start-up times and can require several months to grow sufficient populations of microorganisms that provide wastewater treatment. During this time, sewage like smell might be experienced as partially treated effluent could be produced and sent to the land application area.In order to avoid that, it is recommended, to contact an authorised service technician to come out and inspect the STS system before the STS system can be start after periods of non-use.


All STSs must be provided with an alarm system to alert occupants to an electrical or mechanical malfunction. The alarm must have an audible and visual (indicator light) component. The fault indicators should be located inside the premises, preferably within the kitchen or laundry.


Slight odour from the system is normal. However, strong persistent odours indicate the system is not functioning correctly


Remember that the dedicated irrigation system and irrigation area must function every day of the year - rain, hail or shine. When setting up the irrigation system, the following points should be considered:

  • The required size of the irrigation area should be in accordance with the installation approval (Local Government or Department of Health).
  • The irrigation area must comply with setback distances from the building, boundaries, swimming pools etc.
  • The irrigation area must be landscaped with suitable salt and nutrient tolerant plants and must be designed to discourage or prevent access by pets and people.
  • The recycled water must be evenly distributed over the whole area without spray drift, pooling or runoff.  
  • The irrigation system must not be connected to the reticulated mains supply or other drinking water supply.
  • All distribution pipework for the irrigation system should be buried at least 150mm below the ground surface.
  • The recycled water is not to be used for growing food crops.
  • Roof and surface waters must be diverted away from the irrigation area.
  • The irrigation area must not be located on land subject to flooding or waterlogging.
  • The pump provided in the aerobic system must be of sufficient capacity to ensure an even distribution of recycled water to the whole of the irrigation area.

Wastewater system manual and approval conditions

A copy of the operating and service manual and the approval conditions can be obtained from the system installer, service technician, manufacturer or an Environmental Health Officer of the council where system is installed.

For more detailed information on the operation and maintenance of the STSs refer to the Code of Practice for the Design, Manufacture, Installation and Operation of Aerobic Treatment Units (ATU’s).


Last reviewed: 16-05-2024
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Public Health