The do's and don'ts

The do's and don'ts of operating your on-site treatment and disposal system

Keep the treatment system ‘alive’

Household cleaners, strong detergents and toxic chemicals can kill the ‘good’ bacteria within treatment systems. To keep these bacteria alive:


  • Use biodegradable detergents and cleaners;
  • Check your detergents and cleaners to see if they are suitable for use with an on-site treatment system; and
  • Limit as much as possible the use of bleach-based products such as whiteners, nappy soakers and stain removers.


  • Pour acids, pesticides, medicines, paint, thinners, engine oil or other materials which will kill the bacteria into your treatment system. (These should be disposed of properly at your local transfer station or landfill);
  • Pour grease or cooking oil into your treatment system; or
  • Use septic tank “cleaning chemicals”.

Reduce the solid load

To reduce the sludge build-up in your treatment system:


  • Scrape all your dishes to remove fats and food particles before washing; and
  • Shake sand and dirt from clothes before you wash them.


  • Put sanitary pads, tampons, paper tissues, paper towels, disposable nappies, nappy liners, cigarettes or rags into the system;
  • Use a kitchen waste disposal unit; or
  • Put compostable vegetable matter into the treatment system unless it is specified by the manufacturer.

Reduce the liquid load

Small loads of effluent don’t pass through the treatment system as quickly. This gives the solids in the effluent more time to settle out of the liquid rather than escaping out of the tank into the disposal system.

Less effluent going into the system also means less effluent coming out. Therefore, the soils beneath the disposal system don’t get as wet, providing a more effective final treatment for the effluent.

To reduce the amount of effluent going into the tank:


  • Install water-saving devices eg. dual flush toilets;
  • Take showers instead of baths; and
  • Fix leaking taps.


  • Wash clothes until you have a full load;
  • Do all the clothes washing on the same day. If you normally do more than two full loads of washing per week, try to spread it out over a few days;
  • Empty large volumes of water into the treatment system from spa pools; or
  • Allow stormwater to enter the treatment system, either from the roof or the surrounding land.

Protect the disposal system


  • Restrict access to any areas of land that have been specially planted as part of the disposal system.


  • Allow vehicle or stock access to areas where a disposal system has been installed;
  • Allow stormwater to enter the disposal system, either from the roof or the surrounding land; or
  • Grow deep rooting trees or shrubs over the disposal system.