Septic and wastewater

There are two main types of system. Which one is required depends on where your property is located. Speak to the City's Health Services team before deciding which system to purchase.

Conventional system — the standard option for most properties in Mandurah. It uses two septic tanks and either two leach drains or four soakwells.

Nutrient retentive system — required for properties in environmentally sensitive areas.

Once you have decided which type of system you need, check that the design is approved by the Department of Health before lodging your application with the City.

You need City approval before installing, upgrading or relocating any wastewater system. The process is:

1. Lodge an application through the City of Mandurah Online portal. You will need to attach: 
   • A completed Application to Construct or Install an Apparatus for the Treatment of Sewage 
   • A scale site plan showing the location of the proposed system, any existing systems, and setbacks from structures, paved areas and property boundaries
2. Receive your permit to install. Your plumber must comply with all conditions on the permit.
3. Book a final inspection. Once installation is complete, contact Health Services to arrange an appointment to inspect the system on site.
4. Receive your permit to use before operating the system.

Greywater is household wastewater from the laundry and bathroom (not including the toilet or kitchen). Greywater systems are only permitted in approved areas of Mandurah.

To set up a greywater system:

1. Contact the City to confirm your property is in an approved area
2. Choose an approved greywater system and discuss with a licensed plumber
3. Lodge an application with the City

The City recommends that any septic system should be decommissioned as soon as possible once connection to the sewerage system has been made. Legally, however, decommissioning is not an automatic requirement once sewerage connection is made.

Decommissioning a wastewater system is a legal requirement in the following instances:

• Not more than 60 days after ownership of the property has changed. New property owners are responsible for ensuring that septic tanks are decommissioned and are advised to obtain proof. This process is often negotiated during property settlement
• If the foundations for a building on the premises are to be built closer than 1.2 metres from the septic tank, or a building is to be constructed above it
• Decommissioning must occur before any building works commence
• Within 60 days if there is a ‘material change of use’ of the property. For example, if a residence is turned into a business, the system must be decommissioned not more than 60 days after the change of use has occurred.

To decommission:

1. Have the tank pumped out by an approved contractor
2. Remove the tank and backfill with sand — or if removal is not possible, break the bottom of the tank and backfill with sand
3. Notify the City in writing, including certification from the liquid waste contractor

Note: Non-decommissioned septic tanks must not be paved or built over without City approval.