On-site sewage management

Why are Councils Inspecting? Ensuring our health

A State Government survey of sewage management systems in NSW showed that up to 70% were experiencing some type of failure.  In 1998 new legislation (under the Local Government Act, 1993, Section 68) was introduced that made it mandatory for local councils to monitor and approve the operation of all on-site sewage management systems and ensure that those systems complied with environmental and public health performance standards.

All Councils who have un-sewered suburbs must implement an inspection regime and issue an 1C approval to operate 1D certificate for all on-site sewage management systems in their local government areas. In addition to this, councils must develop an on-site management strategy and keep a database of all on-site sewage management systems.

This new legislation was introduced as a result of the much publicised Wallis Lake incident, where 400 members of the public became severely ill after consuming shellfish from the region. Faulty on-site septic systems were suspected to be the source of virus which caused the illness.

Liverpool City Council estimates there are approximately 3,500 on-site sewage management systems in our local government area. All of these on-site systems are required under legislation to be inspected.  An on-site system is a miniature sewage treatment plant, if it is misused, overworked or incorrectly maintained it will fail and potentially be a public and environmental health risk.

On-site sewage systems inspections

Who is affected?

  • Anyone (owners and occupiers) who has an on-site sewage management system
  • Anyone thinking of installing an on-site sewage management system.

On-site sewage systems include:

  • Aerated waste water treatment systems (AWTS)
  • Septic tanks and adsorption trenches
  • Septic tanks and evapotranspiration beds
  • Septic and pump-out systems
  • Grease traps
  • Wet composting toilets
  • Waterless composting toilets
  • Biological aquatic systems
  • Domestic greywater treatment systems
  • Insinkerators.

What do the inspections involve?

The process for an existing on-site sewage management system is below:

  • You will be notified by mail when Council's Environmental Health Officers are in your area
  • A Council Environmental Health Officer will inspect your system
  • Your system will receive a rating based on the risk - high, medium or low
  • If there are no operating problems you will be given approval to operate
  • If failing you will be asked to do work to rectify the problem
  • Your system will be inspected every 1 to 6 years depending on your risk category (Monitoring Program).

A working on-site system will have a thriving bacteria culture which, through their metabolic activities, breaks down sewage in the septic tank. Once disposed of through the soil, soil micro-organisms further purify the effluent. Unfortunately, many things can go wrong, particularly the beneficial bacteria being killed and soil absorption/filtration capabilities are being degraded over time. This, combined with unsafe effluent disposal practices, can result in serious public and environmental health risks.

Legalisation for On-site Sewage Management Systems

There are a number of laws that govern the approval of on-site sewage management systems (AWTS, Septic Tanks, and Biological Filter systems, etc.) and enforcement of remediation works on on-site systems. These include:

Fines for a system contributing to serious pollution of the environment range from $750 on the spot fine for an individual. Corporations risk on the spot fines of $1,500.

Corporations responsible for contributing to serious pollution of the environment face penalties of up to $1,000,000, plus a further $120,000 for each day the offence occurs, while individuals face penalties of up to $250, 000 plus $60,000 for each day the offence occurs.

Residents Responsibilities

Many residents do not realise that as the septic system owner, they are legally responsible for ensuring the safe and efficient functioning of their system.

Failing septic systems can have environmental and public health effects which reach beyond the residential premise. This was demonstrated in the Wallis Lake oyster incident which resulted in members of the public contracting hepatitis.

Residents are responsible for:

  • Ensuring the on-site sewage management system (OSMS) is desludged when required
  • Ensuring harmful chemicals (bleach, nappy wash, disinfectants) do not enter the OSMS system. This will kill the bacteria involved in digesting the sewage resulting in a smell/failure of the system
  • Ensuring the septic system is not hydraulically overloaded (1-2 loads of washing per day)
  • Ensuring any repairs are made to remedy a failed septic system (Via Council Approval)
  • AWTS owners are required to have their system serviced by a qualified AWTS technician
  • Ensuring that any treated or untreated effluent remains within the boundary of their premise. Treated or untreated effluent leaving the premise may result in a fine
  • AWTS owners must rotate their moveable hose and sprinkler/trickle system around their premises in the designated approved irrigation area so as to prevent pooling and ponding of treated wastewater.

Maintenance and Care for On-site Systems

A failing septic system gives off a number of signs. These include wet and soggy absorption trenches, toilets and sinks draining slowly and the constant smell of sewage. Handy hints for caring for your septic system are listed below:

  • Minimise the use of disinfectants. Disinfectants kill micro-organisms that are essential to septic system functioning
  • Minimise or eliminate the use of dishwashers. Dishwashers use large volumes of water and can overload the On-site Sewage Management System leading to reduced treatment time. This leads to poor quality treated effluent being discharged
  • Be careful in your selection of washing powders. Most washing powders are high in Sodium and Phosphorous. These elements eventually build up in the soil were the effluent is discharged resulting in vegetation being killed off
  • Don't pour excessive amounts of oil and grease down the sink. This will result in an overly large scum layer forming in the septic tank
  • Don't put hygiene products, tampons, nappies etc. down the toilet. This will clog the pipes. Dispose of them in a separate bin instead
  • Do check if your septic system needs a pump out. Over the years, solid sludge will accumulate at the bottom of the tank. This has the potential to block the system. If the sludge level reaches 30 percent of the tank volume, then it is in need of a pump out. As a general rule, most households need a pump out every three years. A constant unpleasant stench from the septic tank usually means that there is excessive sludge build up
  • The monthly use of enzymes (i.e. Actizyme) will nourish bacteria and clean the septic tank. If the tank smells, you could also try adding a 2-3 cup of lime and 2-3 bags of wheat germ. Gypsum can also be added to the irrigation area occasionally
  • Encourage planting of appropriate vegetation near the absorption area to facilitate nutrient uptake. Only plant small growing vegetation 0.5 13 1m in height, as large plants root system will interfere with the irrigation piping. It is not recommended that low-lying vegetables and fruit such as cucumbers and strawberries be grown on an effluent irrigation field. If you have grass on the absorption trench, this must be mowed regularly and the grass removed from the area so that the nutrients are not recycled
  • Prevent the absorption trench from becoming waterlogged by contouring the landscape.

The majority of on-site systems fail because of excessive consumption of water overloading the system. The water consumption of the following household devices is listed below:

  • Showers use 10-30 litres per minute
  • Baths use an average of 120 litres
  • Toilets can use up to 10 litres per flush
  • Washing machines can use up to 100-200 litres per load
  • Dishwashers use up to 50 litres per cycle.

When selecting water using appliances look for AAA rated appliances.

Common Problems

A large part of on-site sewage management systems inspections will be educating the public about septic systems. Of particular concern is the misconceptions held about Aerated Waste Water Treatment Systems (AWTS). Common problems encountered in field during inspections include:

  • Heavy objects placed on absorption trenches - this crushes piping leading to trench failure
  • A consistent sewage smell indicating a failed trench or septic tank in need of a sludge pump out
  • Cracked lids and open inspection holes. This encourages shelter for the breeding of vermin
  • Absorption trenches/effluent application areas not being regularly mowed.
  • Some owners of AWTS units are under the impression that the liquid product generated is of drinking quality. This is NOT the case
  • Owners of AWTS with spray irrigation using high powered sprays or aerosol sprays which is illegal
  • Spray irrigation coming into contact with fruit trees, pools, dams and pets.
  • Surface Effluent Irrigation hoses must be black. Many owners have been attaching the traditional green garden hose. This is dangerous and illegal as guests may mistake it for tap water
  • No chlorine tablets placed in AWTS which means effluent is not being adequately disinfected
  • Absence of Reclaimed Effluent Warning Signs, as shown below, in AWTS disposal areas
  • Extremely strong chlorine smell coming from AWTS. This indicates a very high free chlorine reading which can kill important microorganisms in the soil
  • Some residents not realising that there property is un-sewered. This is mostly a problem with rented properties
  • Internal components of AWTS rotting or missing
  • Grass ingrown into the tank
  • Decorative objects such as ponds placed on top of on-site systems to disguise them. This obstructs maintenance and inspection.


Warning Sign that must be displayed in all irrigation areas for Aerated Wastewater Treatment Systems (AWTS).

Useful Links

Should you require any further information on On-site Sewage Management Systems, Contact Council's Environmental Health Officers:

  • Jason Bullock, Environmental Health Officer
    Phone: 9821 7228








The easy septic guide for homes not connected to the sewer

Certificate of Decommissioning for On-site Sewage Management Systems