What type of Septic Tank do I need?

What Type Of Septic System Do I Need?

There are two main types of waste control or septic systems available in South Australia - the conventional system and aerobic systems.  There are also a range of other systems available, such as composting toilets, reed beds etc however these systems are currently classified as non-complying and as such require approval from the Department of Health (DH) and not the local Council.  If you are looking to install a non-complying system then you should direct all inquiries to the Department of Health (SA).


A conventional septic tank system may be either all purpose or a water closet (WC) only, regardless of which, both systems function in the same manner.  The system consists of two components, the septic tank and a soil absorption field or soakage trench.  The tank will be installed in the ground with an access shaft over the lid opening to allow access for the tank to be pumped out (every 4 years).  The trench system is also under ground and will only be visible via a breather pipe or vent pipe. 

The system takes all household wastewater, the solids settle at the bottom of the tank while the fats float to the surface of the tank.  The liquid portion (effluent) gradually moves into the trench (leaving the solids and fats behind) where it then soaks into the soil.  If the tank is not pumped regularly to remove the solids then these solids will also begin to migrate through to the soakage trench.  This is the main reason that these systems breakdown.  The solids and fats can not be absorbed into the soil but rather clog the soil, which in turn prevents the effluent from soaking away.  The only way the effluent can then escape is to break through to surface level, where it becomes a health hazard.


Aerobic systems fall into two categories Aerobic Wastewater Treatment Systems and Aerobic Sand Filter Systems.  The functioning of aerobic systems differs from conventional septic systems in that they provide a secondary treatment and disinfection process as well as the primary treatment (settling of solids).  The resultant reclaimed water can then used to irrigate designated area of the property.


Aerobic wastewater treatment systems may consist of a one or two tank system.  They include a primary treatment component and a secondary treatment component where the wastewater is aerated and clarified before being stored in a pump chamber.  The pump chamber is where disinfection occurs prior to the reclaimed water being discharged to the designated irrigation area.  This type of system recycles all household wastewater, which is then disposed of via an on-site irrigation system. The on-site irrigation system needs to be a minimum of 200m2 in size and set back 1.5m from the tanks and 0.5m from any boundary. The irrigation area must be planted with appropriate shrubs and the whole area mulched so as to prevent any run off from the site. Some land modification may be required depending on the landscape.

These systems require quarterly maintenance servicing by an accredited agent or trained personnel to ensure the reclaimed effluent complies with the discharge criteria stipulated by South Australian Health Commission (SAHC, 1995), now known as the DHS.  Such servicing will generally cost $50-60 per quarter.


The Aerobic Sand Filter system consists of a septic tank for primary treatment and a sand bed for secondary treatment.  The wastewater upon leaving the septic tank enters a distribution sump, which allows even distribution of the effluent across a bed of sand.  The wastewater is filtered through the sand by gravity to a collection point at the base of the sand bed.  It then flows to a pump chamber where disinfection occurs prior to being discharged to the designated irrigation area.  Aerobic sand filters have few working parts and hence there is no requirement for a service technician to service the system quarterly, however they still require monitoring to ensure that the reclaimed water complies with the discharge criteria.  The primary treatment component also requires regular pump out to ensure effective functioning.


The standard requires that each site be assessed for suitability of any chosen system.  It should firstly be decided which system is preferred, then determine whether it is suitable for your property.  For more information contact Council's Environmental Health Officer, Mrs Emma Mcdonald, 8688 2101 or Mobile 0427 882 202.

It should be noted that this fact sheet is intended as a guide only and does not incorporate all possible circumstances.



Tumby Bay is a beautiful coastal township of 1200 residents, who have chosen to establish livelihoods, raise families and retire in a safe and serene environment.

Contact us

District Council of Tumby Bay

Cnr Mortlock Street and West Terrace

PO Box 61, Tumby Bay SA 5605