Backflow prevention
Backflow is a reverse flow of water that can contaminate our fresh water supply.
If you are a business owner or a property owner where a business is operating, installing a backflow prevention device on your property is the best way to manage backflow risk.
How does backflow occur?
Backflow occurs when water flows from a customer’s pipes back through the meter into GWMWater’s pipes. Backflow is caused by a sudden drop in pressure in the supply pipe.
When the pressure drops, contaminated water can mix with the fresh water in the mains network.
When the system is pressurised again, contaminated water can unknowingly be distributed to other local water users.
What can cause backflow contamination?
Connecting water to equipment used to mix chemicals with water.
Cleaning equipment used on chemical or biological substances.
Connecting water to cooling towers and heating systems.
Connecting water to equipment using recycled water.
Leaving a hose running in a container with chemicals in it.
Sites and processes that can cause backflow contamination
The below list includes examples of sites and processes where backflow contamination is a higher risk.
Motels and hotels
Schools, kindergartens and day care centres
Restaurants, food handling centres
Caravan parks (without sewage dump points)
Hospitals, nursing homes, dental clinics and medical clinics
Shops, commercial laundries and dry cleaners
Premises with grey water re-use systems
Vehicle washing facilities
Some food processing plants
Industrial processes
Fire hose reels
Public swimming pools or ponds
Abattoirs and poultry processing
Agricultural or irrigation use
Mortuaries and funeral parlours
Toxic chemicals, fertilisers and pesticides
Vehicle maintenance garage, service stations, spray painting, panel beating.
What are your responsibilities?
If you are a business owner or a property owner where a business is operating, you are responsible for:
Making sure that any activity on your property does not contaminate the water supply
Using a licensed plumber with the appropriate qualification in backflow prevention to:
Identify your property's hazard rating
Identify the type of backflow prevention device you need
Install and maintain backflow devices on your property appropriate to your property’s hazard rating
If your device is testable, test the backflow prevention device every 12 months. Your plumber must send us the test report within 14 days of the test.
New business customers
When you first apply for Consent to Connect to the Water Supply System, we will let you know if a backflow prevention device must be installed on your property.
Existing business customers
Some existing properties within the network may have the wrong type of backflow prevention device fitted or no device at all. We assess existing water connections for backflow prevention compliance. If your property fits either of these scenarios, you will receive a letter from us explaining why you need a backflow prevention device fitted and what you need to do to make your existing connection safe for everyone.
Complying with this request is a requirement under the Water (General) Amendment Regulations 2025 | legislation.vic.gov.au
What are licensed plumbers responsible for?
If you are a licensed plumber with backflow prevention qualifications, you are responsible for:
Assessing a property's hazard rating. (We will help you to determine the property's rating)
Choosing the appropriate backflow prevention device
Installing and testing the device
Providing the test report to GWMWater within 14 days of the test.
Please email to us at backflow@gwmwater.org.au or contact us.
For more information about plumbers' responsibilities, visit Backflow Prevention | Victorian Building Authority (vba.vic.gov.au).
How do I maintain my backflow prevention device?
As the property owner, you are responsible for arranging installation and ongoing maintenance of a backflow prevention device to your water service.
After your backflow prevention device has been installed by a licensed plumber, and approved by us, your plumber is to provide us with a commissioning test report. Your backflow prevention device must then maintained every 12 months by a licensed plumber. Your plumber must send us the test report within 14 days of the test to email backflow@gwmwater.org.au or by mail, fax or drop it off to us.
Contact us for more information about installing and maintaining a device.