An onsite wastewater management system (OWMS) treats sewage. Sewage is a type of wastewater that contains human excreta, urine or toilet flush water. It includes greywater.
Most sewage goes through Victoria’s sewerage systems for treatment. However, some areas do not have a sewer connection – for example, in some rural areas.
In this case, you can manage your sewage using an OWMS. The system treats the sewage for reuse or disposal.
You need a permit from your local council to install an OWMS. This includes a septic tank system.
A poorly installed or maintained OWMS can release untreated sewage. This is especially true of older systems. Untreated sewage can create significant risks of harm to human health and the environment. Risks can include:
- contaminated drinking water
- contaminated land or water
- offensive smells.
This information is for constructing, installing or altering an OWMS with a design or actual flow rate of sewage not more than 5,000 litres on any day.
For treatment plants that can treat more than 5,000 litres per day, refer to A03 – Sewage treatment.
Construct, install or alter your system
You need a A20 – On-site wastewater management system permit from your local council to construct, install or alter an OWMS.
To apply, you must contact your council. Your system must meet certain standards and any other council requirements under both the planning framework and the environment protection framework.
Your application must include a copy of a valid certificate of conformity for the system.
Altering an OWMS is changing either:
- the design or construction of the system
- the operation of the system
- the place or premises where it's located – for example, moving from a residential premises to a commercial premises, which may increase the hydraulic flow rate or organic load of the system.
Altering does not include general maintenance of the system.
For technical guidance for managing your OWMS, refer to Guideline for onsite wastewater effluent dispersal and recycling systems. This includes information that supports a risk-based approach to designing and using an OWMS.
For guidance on taking a risk-based approach to managing an OWMS, refer to Guidelines for onsite wastewater management.
Meet your legal obligations
The general environmental duty applies to the activities of constructing, operating and maintaining your OWMS. You must eliminate or reduce risks of harm from your OWMS so far as reasonably practicable.
For example, the duty applies to how you:
- construct, install, alter, operate and maintain the system
- deal with faults or system failures
- manage your waste.
Follow a risk management process to:
- identify hazards
- assess risk
- implement and monitor suitable controls.
Owners and occupiers of land with an OWMS also have legal obligations under the Environment Protection Regulations 2021(opens in a new window). These requirements apply to all systems, including older systems that did not have a permit when they were installed. Your local council can enforce these laws.
These obligations include:
- taking all reasonable steps to make sure the system is operating so that it does not pose a risk to the environment and human health
- making sure the system does not overflow
- notifying the local council if the system poses a risk to human health and the environment, or if there's a problem with the system
- taking reasonable steps to maintain the system in good working order (this obligation does not apply to residential renters).
Owners must also:
- provide written information about how to use the system to the person in management or control of the system – for example, a renter
- keep maintenance records and provide them to council when requested.
Sewage from an OWMS is considered priority waste under the Environment Protection Act 2017(opens in a new window) and Regulations. When septic tanks are pumped out, all reasonable steps must be taken to make sure the waste is taken to a place that's authorised to receive it (lawful place).
Local councils enforce the Regulations. They can take enforcement action if you do not comply.
Maintain your system
To make sure your system is functioning properly, it's important that you maintain it. All treatment plants should be maintained following the manufacturer's recommendations.
Make sure your system can be easily accessed for maintenance. Professionals, such as a licensed plumber or accredited servicing agent, can make sure the system is functioning correctly. For example, they can:
- check if your system needs cleaning and unblocking
- install an alarm to warn you of breakdowns
- de-sludge the system
- check and/or fix pipes, tanks and storage systems.
A good maintenance process avoids:
- driving vehicles over any part of the system
- allowing stormwater to discharge into the system or over the disposal and/or drain field
- covering the tank or the drain field.
For more information on how to maintain your system, refer to Guidelines for onsite wastewater management.
If your property has been affected by fire or flood, get a licensed plumber or service technician to assess your system.
Maintain the disinfection chamber
Chlorine tablets must be fitted to the dispenser in the right way.
If the system is fitted with UV disinfection, UV light tubes must be cleaned regularly.
Reduce sludge build-up in the tank
Over time, layers of sludge and scum build up in the system. These layers need to be removed for the primary settling tank to function properly. This means you need to de-sludge your system.
How often you need to de-sludge your system depends on many factors, including how much the system is used and the manufacturer requirements.
To reduce sludge:
- scrape all dishes to remove fats and grease before you wash them
- do not put solids in the system
- do not use a food waste disposal unit unless your system can carry the extra load
- do not put hygiene products – for example, sanitary napkins and tissues – in the system.
Keep microorganisms working well
Not all microorganisms are harmful. Some microorganisms in your OWMS help convert your waste to liquid and gas. To manage microorganisms:
- use biodegradable soaps and detergents that are low in phosphates
- use detergents that are low in salt
- use the right amount of detergents
- do not put chemicals or paint down your drain
- do not put non-biodegradable items or rubbish into the system.
Avoid powerful chemicals
Try to avoid using chemicals that impact how well your system works. These include:
- powerful bleaches
- whiteners
- nappy soakers
- spot removers
- disinfectants.
Reduce the amount of wastewater you produce
To reduce the amount of wastewater that enters your system:
- install water saving fittings
- take showers instead of baths
- wash only full loads of clothes.
Avoid overloading your system
To space out your water use, avoid:
- doing all your washing in one day
- running your dishwasher and washing machine at the same time.
Deal with incidents and faults
It's essential to be vigilant about potential failures, especially with older legacy systems. This means paying attention to key warning signs and taking steps to address issues. Do this even if an issue is contained to your property.
Warning signs of failure may include:
- the absorption field becoming wet, with wastewater pooling on the surface
- wastewater run-off from the disposal area
- a smell of effluent near or from the system
- drains or toilets running slowly
- the grease trap being full or blocked.
As the landowner or occupier, the Regulations require you to tell your council if your system shows any signs of failure. You need to explain what you have done, are doing or propose to do to fix the problem. If other people detect and report issues to council – such as offensive smells – and you have not reported it, a penalty may apply.
Decommission old systems
Groundwater contamination can happen if old wastewater management systems are left in place.
In most areas of Victoria, septic systems must be decommissioned when they're not needed anymore – for example, when a property is connected to the mains sewer.
Decommissioning means emptying and cleaning out the tank and making sure it cannot be used again. This helps minimise risks of contamination.
However, if any waste leaked into the ground, this area can remain contaminated. How long it's contaminated depends on where the system was and how it was installed.
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