Septic Tank & Aerobic Wastewater System Maintenance

New Systems

Whether you choose a standard septic system or an aerobic wastewater system it will need to undergo a settling in period in which the required bacteria establish themselves.  During the first few weeks of operation there may be some odour associated with the tank from vents in the system.  This is normal.  The odours should reduce once the tank has settled in and the necessary bacteria have established themselves.

For a waste control system to function efficiently the tank needs to operate under alkaline conditions. Under normal operation the tank will be in an alkaline condition however, the balance of the tank can be compromised due to a number of ways:


Excessive use of cleaning chemicals

  • Shock volumes of incoming water from washing machines or spa baths
  • Lack of use of the system if the house has been vacant for some time
  • Allowing sanitary napkins, facial tissues, disposable nappies or similar items to enter the tank


Odour Problems

If conditions in the tank become acidic the normal bacteria may die off which will result in offensive odours. This can be rectified by using hydrated lime which is available from hardware stores. It is recommended to mix 0.5kg of lime with 10 litres of water which is flushed down the toilet 2 or 3 times a day for 3 to 4 days until a total of about 5kg is used. The balance of the tank should return in about a week. If odours are still present after that time more lime may be required.


General System Maintenance

Mosquito control

  • Ensure vents have mosquito-proof mesh fitted
  • Ensure inspection openings and tanks are sealed to prevent mosquito entry


  • Only use products labelled as biodegradable or safe for septic tanks
  • Follow directions for use and use only in moderation
  • Where possible use alternative cleaners such as bicarb of soda, borax, vinegar etc

Toilet paper

  • Use only biodegradable toilet paper. Facial tissues, sanitary napkins, tampons and disposable nappies should not be flushed down the toilet

Food scraps

  • All food scraps should go into your domestic waste bin or compost, not down the sink


  • All types of septic systems require desludging by professional contractors at least every four years. Some tanks may require pumping out more frequently depending on the size of the tank and whether it is for domestic, industrial or commercial use.


Aerobic Wastewater Treatment Systems

As a condition of approval, all aerobic wastewater treatment systems are required to be serviced by the system manufacturer or an accredited service agent at three monthly intervals or as recommended by the manufacturer in the service manual. This may include checking the blowers, contact media, pipework, valves, diffusers, effluent clarity, sludge return, removal of excess scum, testing the pump and general operation of the system. A supply of chlorine tablets sufficient to last until the next scheduled service must be installed in the unit.


Prohibited discharges

  • Stormwater from downpipes or rainwater tank overflows
  • Trade waste from commercial premises
  • Backwash water from swimming/spa pools
  • Paint, petroleum products or other solvents, strong alkalines or acids


Further Information

For more information contact Council's Environmental Services section on 08 8563 8481.