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What is CWMS

Council's Community Wastewater Management System (CWMS) is a wastewater drainage system. The CWMS takes liquid wastewater (effluent) from properties that have a septic tank system to SA Water sewer mains or an approved treatment facility.

Households on CWMS have a septic tank which requires routine cleaning once every four years. Council manages this process to ensure the minimum cleaning requirements are adhered to.

Following recent State Government announcements we are currently working with SA Water to help develop a program for the connection of properties on CWMS to SA Water's sewer system. Here is the latest update from SA Water - SA Water update January 2021(PDF,446KB). For more information visit SA Water's water talks page.

At the 9 March Council meeting, community members raised a number of questions as part of the public forum. These questions have been answered through an Information Report to Council(PDF,151KB) .  

The video explains what CWMS is and how it works. But, if you're still unsure or have any questions, please fill out the CWMS feedback form


Properties on CWMS

Use the map to navigate to an address. Highlighted properties are on CWMS



An annual service charge applies to properties connected to CWMS and is incorporated in the council rates bill (see also Council rates). This charge is instead of sewer fees which would be payable to SA Water if a property was connected to sewer. Any CWMS charges collected by Council must be used to keep the system operational for current and future users of the system. For examples of related expenses and more information, see the Frequently asked questions - Finance below.

Development on a property connected to CWMS

There are certain developments on your property that will require Council development approval

If your property is connected to the CWMS, in addition to Council development approval, you may also require a separate approval from the Water Operations Team or the Environmental Health Team. These activities and the required approvals are detailed in the table below:


Water Operations

Environmental Health

Connection to CWMS (includes new connections, drain extensions and modifications)



Trade waste approvals or changes in trade waste agreements



Installation of a new trade waste system



Building a new house



Installation of a new septic tank



Additions to an existing building that include plumbing works



Installation or modification of a swimming pool



Installation or modification of a spa



Draining a swimming pool or spa



Installation of a pumped septic system




Subdividing properties connected to CWMS

As a part of the land division process, Council will determine what is required to achieve new CWMS connections for the proposed development.

A separate CWMS application will need to be lodged for a full assessment and a quote to be prepared. Costs associated with alterations to the CWMS and new connections to the CWMS need to be paid by the land owner prior to final clearance of the land division. For more details refer to the CWMS FAQs.

Building over CWMS infrastructure

In general, Council will not approve the construction of any structure over or under any CWMS infrastructure. This is to ensure that Council has access to its infrastructure for maintenance and repair purposes. For more details refer to the CWMS FAQs, or read Encroachment Over Community Wastewater Management System Infrastructure Information Sheet.


Swimming pools and spas

If your property is connected to CWMS, and you have, or want to install a swimming pool or spa, approval from the Water Operations Team is required. Submit your application to the Water Operations Team using the online form 

Unauthorised discharges into the CWMS can create serious environmental health issues for other customers on the same line due to the increased pressure in the network.  For more details refer to the CWMS FAQs below or EPA website



If there is a blockage on your property, call a licenced plumber and let them know you are on a septic system. It is important for plumbing work to be undertaken by a licensed plumber as this may have implications with your insurance or any warranties you may have.

Frequently asked questions - Plumbing & maintenance

What is a septic system?

A septic system treats and disposes of wastewater from toilets, bathrooms, laundries and kitchens. Simple care and maintenance of your septic system can prevent contamination to the environment and protect the health and safety of your family.

A septic system is made up of various components including:

  • Septic tank
  • Internal drains
  • Tail pipe
  • CWMS main and connection point. 

What is a septic tank?

Septic tanks have been used in un-sewered areas for many years as the first stage of treating domestic wastewater.

A septic tank is an underground watertight tank made from either concrete or plastic. Your septic tank should be located within the boundary of your property.

Wastewater from your toilets, laundry, bathrooms and kitchen is gravity fed into the septic tank for treatment, where the liquid and solid portions of the waste are separated.

The solids settle to the bottom of the tank where naturally occurring bacteria convert the material into sludge, while the liquid effluent passes out of the septic tank, through your system’s outlet drain and into Council’s Community Wastewater Management System (CWMS).

What is an access hatch and why do I need it?

Your septic tank is required to have a hatch to provide access for cleaning (pumping out). A licensed contractor must complete the pump out, and if you are connected to Council’s CWMS, this will be organised by Council and done every four years. Council’s contractors are licensed by the EPA to remove, transport and dispose of the waste.

In general, if your septic tank is working well, you should not need to open your septic tank. If you are required to open the access hatch, take care as wastewater can produce harmful gases.

It is a requirement that all new septic tanks have their access hatch raised to ground level. This must not be covered by anything that cannot be quickly and easily removed. Older septic tanks may not have their access hatch at ground level. For ease of access, it is recommended that home owners engage a contractor to raise the access hatch (lid).

What is an inspection point?

The inspection points (IP), located on the inlet and outlet drain of the septic tank, enable access to the sanitary drain to clear any potential blockages. A licensed plumber can assist in clearing these blockages if they occur. If you do not have visible IPs at these points, consider speaking to your licensed plumber about raising them to ground level.

What is a CWMS connection point?

The connection point is the point where wastewater enters Council’s CWMS. The connection point must not be covered as Council may need to access it from time to time.

Any maintenance of the CWMS drain, from the connection point is Council’s responsibility whereas any maintenance from the connection point up to and including the household drains is the responsibility of the property owner (see figure 1.)

Figure 1: Diagram illustrating what is Council’s responsibility and what is the property owner’s responsibility.


Please note, if you wish to raise the ground level of your property (e.g. when building a retaining wall or building a garden bed), you will need to contact Council for approval, and if approved, you will be required to pay for the connection point to be correctly positioned at the new ground level.

The photos below (figure 2) are examples of what your connection point may look like when it is raised to ground level.



How do I maintain my septic system?

Maintaining your septic tank and its associated drains is important because it will save you time, money and help protect the health of your family and property. Damaged drains should be repaired quickly to help prevent reoccurring blockages. SA Health’s fact sheet has some valuable information regarding maintenance of your system. 

Does my septic system require a pump?

Whenever possible, a septic tank system should be designed with sufficient grade on the drains so that wastewater can flow to the CWMS by gravity.

A pump system may need to be installed when there is insufficient fall for the wastewater to flow from the septic tank to the connection point. Please note, approval is required to pump wastewater into Council’s CWMS network.

What do I do if I need to replace my septic tank?

As the tank ages it may need to be replaced. Replacement of your septic tank requires wastewater works approval from Council. The septic tank and all other plumbing must be installed by a licensed plumber. The septic tank must be on the approved

products list which can be found on the SA Health website.

How do I know if a blockage is in my drains or Council’s CWMS drain?

Locate the connection point. It is typically located near the front or rear boundary of your property. If you have trouble locating the connection point, Council can provide some assistance to help you find it.

If there is no water flow observed through the connection point when you turn on a tap in your house, the blockage is most likely on your property. If this is the case, contact a licensed plumber to clear the blockage.

If water is holding at the connection point, the blockage is most likely in Council’s drain and you should call us on 8397 7444 so we can send someone from Council to assess and clear the blockage.

It is normal for your septic tank to appear full because of the design of the septic tank.

Is my plumber a licensed plumber?

It is important to check that the plumber you are using is licensed. You can request to see their identification card which should contain their licence number. The licence number can then be checked using the Consumer and Business Services website.

An unlicensed plumber may not undertake the required work correctly which may result in damage to your property and potentially impact any insurance claim or other warranties you may have.

How do I know if I have an SA Water sewer connection?

If you have an SA Water sewer connection, your SA Water bill will include a sewerage access charge for the removal and treatment of sewage and used water from your property. It is based on your property value as determined by the Valuer-General.

Under Council’s new CWMS Infrastructure Management Policy , CWMS customers who have an existing SA Water sewer connection point can apply for a payment plan from Council to connect to SA Water’s sewage system. Council will contact eligible properties in 2020-2021 financial year to discuss this opportunity.

Can I connect to the SA Water sewer system instead of the CWMS?

You will need to apply to SA Water to connect to their wastewater network. Be aware there are costs associated with this process. If your application is approved by SA Water, you will need to inform Council's Water Operations Team.

Do I need approval to discharge swimming pool or spa wastewater into the CWMS?

Yes you do. When a swimming pool is backwashed or emptied, the wastewater is generally pumped into the CWMS main. The CWMS network relies on gravity flows to drain wastewater from each of the connected properties and cannot manage pumped flows above 1L/s. Council needs to know when this will happen to manage the amount of flow into the system and prevent wastewater overflows.

Council requires pool owners who are connected to CWMS to install a flow restriction device to limit the flow to an acceptable rate.  Your pool drainage line must include 2 x inspection openings and an isolation valve to allow Council staff to test the flow rate before allowing the pool to be connected to your septic outlet pipe.  The arrangement should look like this:


Wastewater from your pool or spa must bypass your septic tank and be discharged to the outlet drain between your septic tank and the CWMS connection point. 

You should plan to backwash or drain your pool or spa in off-peak times to avoid causing disruption to the CWMS service for other residents.  The best times for backwashing or draining are between 10:00pm and 6:00am for periods no longer than 30 minutes.

For additional information about disposing of wastewater from swimming pools or spas see the EPA website

Is it ok to drain stormwater into CWMS?

No, it isn’t.  Residents must not allow any rainwater, stormwater or surface water to enter the CWMS.

If stormwater enters the CWMS, the network can become seriously overloaded during and after rain events.  When the CWMS is overloaded, septic tanks cannot efficiently drain into the network and this appears as though the drain is blocked. In extreme cases, the CWMS may overflow creating an environmental hazard.

Frequently asked questions - Planning

Is the CWMS network stable?

While Council’s CWMS network is stable, like all utilities, it requires maintenance to remain operational. Council’s plan for upgrading the system will be implemented as it reaches the end of its serviceable life. This is predicted to occur over the next few decades.

In 2018-2019, 74 sewer overflow events per 100km of network were reported. This is comparable to SA Water’s performance, which recorded an average of 86 sewer overflows per 100 km of network (source: SA Water Regulatory Performance Report 2017-2018).

What work does Council undertake to operate and maintain the CWMS network?

Council’s CWMS Asset Management Plan sets out a rolling program of renewal and upgrade works. We also proactively inspect and monitor the system, assessing its condition and the flow of wastewater through the network of pipes, as well as undertake asset rehabilitation where required.

In the last two years (2017-2018 to 2018-2019), we have assessed the condition of about 9% of the CWMS pipe network (or 10 kilometres of pipe). We will continue to assess the condition of a minimum distance of 1km of pipe each year. In the last 10 years, we have also upgraded 2.4 kilometres of sewer pipes at a cost of $2.06 million and pumped out an average of 1,100 tanks per year.

How does the CWMS Infrastructure Management Policy affect me if I live in the Modbury Precinct?

Under Council’s new CWMS Infrastructure Management Policy , properties serviced by CWMS located within the Modbury Precinct will be converted to SA Water’s sewage system. Council will assist property owners with this process.

The cost of conversion is the responsibility of the property owner. To minimise the financial impact, Council will offer a payment plan.

Frequently asked questions - Finance

What does my annual CWMS charge cover?

Council is licensed by Essential Services Commission of South Australia (ESCOSA) to operate as an intermediate water retailer under the Water Industry Act (WIA) 2012. Under the licence terms, Council is required to ensure service pricing covers the full cost of operations and maintenance of the system as well as full cost recovery of capital expenditure.

The CWMS annual service charge is based on projected operational and maintenance costs as well as capital expenditure from Council’s CWMS Asset Management Plan.

The annual service charge applies to properties connected to CWMS and is incorporated in your council rates bill. This charge replaces the sewer fees which would be payable to SA Water if your property was connected to sewer. 

Any CWMS charges collected by Council must be used to keep the system operational for current and future users of the system. Some examples of CWMS related expenses include:

  • The operation and maintenance of CWMS network
  • Renewal and upgrade of CWMS mains
  • Routine pump outs of septic tanks connected to CWMS 
  • Fees charged by SA Water to accept wastewater from CWMS into their system for treatment - about $700,000 annually
  • Costs associated with depreciation, capital and risk.

What are the costs associated with CWMS?

Yearly CWMS service fees are $725 or $480 for those charged an SA Water abuttal fee. Other costs associated with CWMS can be found in Council's Fees & Charges Register

Why can’t general rate revenue be used to cross-subsidise CWMS customers?

Legislative changes by Essential Services Commission of South Australia (ESCOSA) mean that Council has to recover the full cost of operating and maintaining the CWMS network from users of the service. Costs were previously subsidised, with about $900,000 of general rates revenue re-invested in the system in 2018–2019 – that’s about a $193 subsidy per connection. If there was no subsidy, the current annual charge would be $843 instead of $725. As this is no longer possible, annual CWMS charges will gradually increase over the next four years until full cost recovery is reached in 2022–2023. The increase for 2020–2021 is $75.

Will the annual service charge continue to increase?

Legislative changes by Essential Services Commission of South Australia (ESCOSA) mean that Council has to recover the full cost of operating and maintaining the CWMS from users of the service. As a result, the annual CWMS service charge will gradually increase over the next four years until full cost recovery is reached in 2022–2023. The increase for 2020–2021 is $75.

Where have the funds collected from the annual CWMS service charge been invested?

Residents on CWMS pay an annual service charge, which is used to cover the cost of operating and maintaining the system, renewal and upgrade of the mains, routine pump-outs of septic tanks, service support, fees charged by SA Water to accept wastewater into their system for treatment, as well as costs associated with depreciation, capital and risk.

Historically, the money collected through the annual CWMS service charge has been insufficient to cover these costs. In 2019-2020 about $900,000 of general rate revenue was re-invested in the system to cover the shortfall.

The requirement by Essential Services Commission for Council to operate the CWMS on a full cost recovery basis means that general rate revenue can no longer be used to subsidise the system, meaning the annual CWMS charges will gradually increase over the next four years until full cost recovery is reached in 2022–2023.

Over the last 10 years, Council has renewed about 2.4 kilometres of CWMS mains at a total cost of $2.06 million, assessed the condition of more than 10 kilometres of pipe (or 9% of the network) in the past 2 years, and pumped out an average of 1,100 tanks per year. We have also paid SA Water approximately $6.1 million in fees during this time.

Can I connect to the SA Water sewer system instead of CWMS?

You can apply to SA Water to connect to their wastewater network. Be aware there are costs associated with this process. If your application is approved by SA Water, you will need to inform Council's Water Operations Team. Visit - connections - fees

Who will bear the cost of conversion from CWMS to SA Water's sewer system?

Currently the cost of conversion is the responsibility of the property owner. To minimise the financial impact, Council will offer payment plans. Please contact Council to determine if you are eligible for a payment plan.

Given the recent state government announcement to commit $65M to connecting all CWMS properties to SA Water, SA Water are working towards developing a program and associated costs and we hope that the commitment by State Government will enable all current properties to connect to SA Water.

Until such time as we receive a conversion program from SA Water, the cost of renewals and upgrades will be funded from developer contributions, the annual service charge and grant funding.

Difficulty paying CWMS fees

If you are on a low or fixed income, or experiencing financial hardship, you may be eligible for state government assistance through the cost-of-living concession and /or the sewerage concession. For more information visit 

Trade waste information

What is trade waste?

Trade waste is any wastewater that is generated from an operating business.
Trade waste generally requires additional treatment, which is business specific.

Do I need authorisation?

If you are operating a business, you must have the appropriate trade waste authorisation. Under the Water Industry Act 2012 it is illegal to discharge unauthorised trade waste into Council’s CWMS network.

How do I apply for authorisation?

Trade waste authorisation can be obtained by lodging an online application with Council.

Please note, if you are installing a new trade waste system, and are connected to Council’s CWMS, you will need to apply for a wastewater works approval under the South Australian Public Health (Wastewater) Regulations 2013.

To obtain a trade waste authorisation you must provide the following information as part of the application. You may need to consult with a Wastewater Engineer.

Information required for trade waste authorisation application

  1. Owner of business entity
  2. Name of business entity
  3. Business address
  4. Contact details
  5. Type of business activity
  6. Hours of business operation
  7. Proposed rate of wastewater discharge
  8. Name of all chemicals used at the business premises (including up to date SDS for each chemicals used on site)
  9. Wastewater drainage and stormwater drainage plans
  10. Type, specification and size of all pre-treatment devices

Trade Waste Authorisation

The authority to discharge trade waste, which is granted by Council, is site specific. Businesses which operate from multiple sites will require a trade waste authorisation for each site.

The conditions of the trade waste authorisation will impact the type of pre-treatment and plumbing work that is required. Council trade waste authorisation is required before the works are undertaken.

  1. A trade waste discharge authorisation cannot be transferred or reassigned to another party and ceases when there is:
    1. A change in the ownership of a business; or
    2. A change in the location of the business; or
    3. A change in discharge requirements from SA Water; or
    4. A change in legislation.

Business entities must notify Council when there is a change in business operations, including a significant change to the quality and quantity of trade waste. The online form can be used to notify Council.

Landowner and tenant/lessee relationship

The application for trade waste authorisation must be made by the business entity.  The business is responsible for compliance with the conditions of the trade waste discharge authorisation.

If a business owner refuses to seek trade waste authorisation or refuses to comply with the conditions of the trade waste authorisation, Council may take action under the Water Industry Act to prevent further discharge of unauthorised wastewater.

Pre-Treatment of Trade Waste

Trade waste is pre-treated using physical, chemical and biological methods to improve the quality of wastewater before it is discharged into Council’s CWMS network.

Most trade waste can be treated using the common pre-treatment devices shown in table 2 below.

Table 2 Examples of pre-treatment devices

Pre-treatment Device


Grease arrestors

Used to intercept grease and fat. Typically required when hot food is prepared on the premises. Some examples include, butchers/poultry processors, cafes, restaurants, canteens, food courts and bistros.

Dry basket arrestor with fixed screens

Used to intercept food scraps and solid waste. Typically required when there is a risk of solids entering the CWMS. Some examples include bakeries, cafes, restaurants, canteens, food courts, bistros, butcher/poultry processors, places where food is prepared and hairdressers.

Sink screen/strainer

Used to intercept food scraps and solid waste. Typically used for hairdressers.

Cooling pits

Used to cool down hot liquids. Often used at laundromats.

Oil water separators

Used to separate oil from water. Typically required for pre-treatment of wastewater in the automotive industry.


The trade waste authorisation will have conditions relating to maintenance of the pre-treatment devices. These conditions are developed from the information provided in your application. It is the responsibility of the business to ensure that all pre-treatment devices are regularly serviced and maintained in accordance with the conditions detailed in the trade waste authorisation.

For guidance on basic pre-treatment requirements, please refer to SA Water basic pre-treatment requirements.


Trade Waste Audits

Council undertakes random audits to monitor business compliance, which may include water quality sampling.

For examples of businesses which generate trade waste, refer to the SA Water Basic Trade Waste Pre-Treatment Requirements information sheet

If you're still not sure about how CWMS works or have further questions, submit our CWMS feedback form

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