Sewage is wastewater that comes from toilets, bathrooms, kitchens and laundries.

Most sewage goes through Victoria’s sewerage systems for treatment.

Sometimes it’s not practical, or possible, to connect to the existing sewerage system. In that case you can manage sewage using an on-site wastewater management system (OWMS) such as a septic tank, composting toilet or secondary treatment system.

How to manage your on-site system the right way

Poorly installed or maintained systems can be a risk to human health and the environment. This is especially true of older systems. Risks can include:

  • polluted drinking water
  • land and waterway contamination
  • offensive smells.

How to build, install or change your OWMS

You need a local council permit to build or install an OWMS that can treat up to 5,000 litres daily. You need an EPA permission to install and run an OWMS that can treat more than 5,000 litres daily.

You need a local council permit to change an OWMS's construction or design. This includes changes that increase the system's flow or load.

How to maintain your OWMS 

  • Ensure you can access your system easily.
  • Use licensed plumbers to assess whether your system needs cleaning and unblocking.
  • Desludge the system every three to five years. How often depends on the level of system use.
  • Take all reasonable steps to ensure the system is maintained properly and keep all system maintenance record.
  • Have an accredited servicing agent install an alarm to warn you of breakdowns.
  • Maintain the disinfection chamber. This chamber uses chlorine to disinfect the treated water. Chlorine tablets must be fitted to the dispenser in the right way. If fitted with UV disinfection, UV light tubes must be cleaned regularly.
  • Don’t drive vehicles over any part of the system.
  • Don’t allow stormwater to discharge into the on-site system or over the disposal/drain field.
  • Don’t cover the tank or drain field.
  • Don’t place non-biodegradable items or rubbish into the system. Bacteria and other organisms can't break down these items or rubbish.
  • Make sure you follow any local council maintenance requirements.

How to keep your OWMS working well

To reduce sludge build up in the tank:

  • scrape all dishes to remove fats and grease before washing
  • don't put solids in the system
  • don't use a food waste disposal unit unless your system can carry the extra load
  • don't put hygiene products in the system. For example, sanitary napkins and tissues.

Not all bacteria are harmful. Some of the bacteria in your OWMS converts your waste to liquid and gas. To keep bacteria working well:

  • use biodegradable soaps and detergents that are low in phosphate. Phosphates feed algae that pollute waterways.
  • in dispersive soil areas, use detergents that are low in sodium
  • use the right amount of detergents
  • don't put chemicals or paint down your drains.

Powerful bleaches, whiteners, nappy soakers, spot removers or disinfectants can impact how well your system works. Try to avoid using them.

To reduce the amount of wastewater you produce:

  • install water saving fittings
  • take showers instead of baths
  • wash only full loads of clothes.

To avoid overloading your OWMS, space out your water use. For example:

  • Don't do all your washing in one day.
  • Don't run your dishwasher and washing machine at the same time.

How to deal with system failures

You must monitor your system for potential failures, especially older systems. This means watching for warning signs, including:

  • foul smells coming from or near the system
  • slow running toilets or drains
  • full or blocked grease trap
  • wastewater runoff from the disposal area
  • wastewater pooling on the disposal field's surface.

You must take steps to address any issues as soon as possible.

How you can use wastewater from your on-site system

On-site systems can treat wastewater to meet three standards: 

  • Primary quality: safe to go directly into soil. 
  • Secondary quality: suitable for surface irrigation use, but don’t put directly into soil. 
  • Advanced secondary quality: suitable for use in your toilet or washing machine. Also suitable for surface and underground irrigation.

What the Environment Protection Act 2017 means for duty holders

The general environmental duty (GED) is at the centre of the Act. It applies to all Victorians. The GED requires you to reduce the risk of your activities harming the environment or human health.

There are many ways you can comply with the GED. For example:

  • Keep your wastewater or septic system in good working order.
  • Manage the risk when disposing the treated sewage to the land.

The Environment Protection Regulations 2021 (Part 5.7, On-site wastewater management systems) requires the following for on-site wastewater management systems:

  • The system should be operated and maintained properly.
  • Duty to provide information to the land occupier.
  • Duty to notify council,
  • Duty to keep and provide maintenance records
  • Council may order maintenance

More help for managing your OWMS

Code of practice – Onsite wastewater management (publication 891)

Victorian land capability assessment framework, Municipal Association of Victoria

Maintaining septic systems under 5000L video

Contact your local council for more information.

Read more about wastewater

About wastewater

About greywater

Onsite wastewater treatment systems with valid certificates

Regulatory framework and approval process for onsite wastewater treatment systems

Wastewater guidance for industry

Reviewed 8 December 2021