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Backflow prevention

Backflow is when water flows backwards into the public water supply network from a private property and is one of the biggest risks to the water supply.

It is a potential source of contamination that can seriously affect the quality and safety of our drinking water, which could cause illness or death. For these reasons all connections to council water supply must be completed by a Council approved contractor.

What causes backflow?

The two main causes of backflow are:

  1. When the public water supply network is at a lower pressure than the water pressure on a private property, water will flow backwards into the public water supply network.
  2. If the public water supply network is directly connected to equipment, which is at a higher pressure, water will be forced back into the public water supply network

This backwards flow can come from residential, commercial, and industrial properties and can be prevented by installing a backflow prevention device at the property boundary.

Preventing backflow

Since 1997, all new properties in Tauranga must have a backflow prevention device fitted to their water supply. Backflow manifolds were installed at all other properties throughout the city when new water meters were installed or replaced.

The installation of a backflow prevention device at the point of supply is a condition of supply and is to be fitted before the water supply connection is installed. If other high risk hazards are identified on site, we will advise property owners that a greater level of protection is required.

As a property owner you have a legal obligation to install the appropriate backflow prevention devices to protect the water on your property and ensure you don’t contaminate the public water supply network. Your obligation starts at the water meter and includes your entire property’s water system.

Backflow Prevention, Protecting your Health (415kb pdf)

Level Definitions What to do
Low level risk Has the potential to create discomfort due to changes in smell and taste. Council installs backflow protection at the boundary for each property which will protect the local network for low level risk activities.
If you have areas within your premises that could create a risk to your drinking water, call council or your plumber* for advice. Your local hardware or plumbing store sells devices that can provide this level of protection e.g. hose pipe protection.
Medium level risk Has the potential to make people ill. Call council for advice and arrange for an assessment and installation of medium or high level protection.
High level risk Has the potential to cause loss of life Call council for advice and arrange for an assessment and installation of high level protection.

* Check your plumber has experience in backflow protection.

Backflow risks and solutions

We use the following criteria to determine the level of backflow protection required for boundary protection and the acceptable solution for that risk. It is an approved document from the Building Industry Authority for Water Supplies, G12, Reprinted Incorporating Amendments 1, 2 and 3.

Water Supplies Acceptable Solutions G12/AS1

Type of hazard

Acceptable devices

Backflow prevention standard/industry solution


Any condition, device or practice which, in connection with the potable water supply system, has the potential to cause death.

  1. Autoclaves and sterilisers
  2. Systems containing chemicals such as anti-freeze, anti-corrosion, biocides, or fungicides
  3. Beauty salon and hairdresser's sinks
  4. Boiler, chiller and cooling tower make-up water
  5. Car and factory washing facilities
  6. Chemical dispensers
  7. Chemical injectors
  8. Chlorinators
  9. Dental equipment
  10. Direct heat exchangers
  11. Fire sprinkler systems and fire hydrant systems that use toxic or hazardous water
  12. Hose taps associated with High hazard situations like mixing of pesticides
  13. Irrigation systems with chemicals
  14. Laboratories
  15. Mortuaries
  16. Pest control equipment
  17. Photography and X-ray machines
  18. Piers and docks
  19. Sewage pumps and sump ejectors
  20. Sluice sinks and bed pan washers
  21. Livestock water supply with added chemicals
  22. Veterinary equipment
Air gap*

Reduced pressure zone device
G12/AS1 Figure 1

AS 2845:Pan 1
Note: The examples given are not an exhaustive list.  Where there is doubt comparison must be made to the hazard definition.


Any condition, device or practice which, in connection with the potable water supply system, has the potential to injure or endanger health.

  1. Appliances, vehicles or equipment
  2. Auxiliary water supplies such as pumped and non-pumped fire sprinkler secondary water
  3. Deionised water, reverse osmosis units and equipment cooling without chemicals
  4. Fire sprinkler systems and building hydrant systems
  5. Hose taps and fire hose reels associated with Medium hazard
  6. Irrigation systems with underground controllers
  7. Irrigation without chemicals
  8. Livestock water supply without added chemicals
  9. Untreated water storage tanks
  10. Water and steam cleaning
  11. Water for equipment cooling
  12. Drink dispensers with carbonators
  13. Swimming pools, spas and fountains.
Air gap*

Reduced pressure zone device

Double check valve
G12/AS1 Figure 1

AS 2845:Part 1

AS 2845:Part 1
Note:  The examples given are not an exhaustive list.  Where there is doubt comparison must be made to the hazard definitions.


  1. Hose tap used for fixed domestic irrigation systems
  2. Facilities used for the storage or preparation of food and beverages
Air gap*

Reduced pressure zone device

Double check valve

Hose connection vacuum break
G12/AS1 Figure 1

AS 2845:Part 1

AS 2845:Part 1

AS 2845:Part 1

Source: Building Industry Authority , October 2001

*Air gaps are for internal protection only. Alternative boundary protection must also be installed. (E.g. If risk is ‘medium’, a testable double check backflow prevention device is required).


Not all devices will cover all backflow risks. The below table details what type of device protects from what type of backflow in some given risk situations. Information around what backflow prevention device is appropriate should be advised by a qualified engineer or council.

Type of backflow prevention

Cross connection hazard





  back -pressure back-siphonage back-pressure back-siphonage back-pressure back-siphonage

Air Gap

(Note 1)







Reduced pressure zone device







Double check valve assembly (Note 2)    





Pressure type vacuum breaker(Note 3)  






Atmospheric vacuum breaker(Note 4)  







  1. Air gaps must not be installed in a toxic environment, and are for internal protection only. Alternative boundary protection must also be installed.
  2. Double check valves can be installed in a medium and low hazard toxic environment.
  3. Pressure type vacuum breakers are designed to vent at 7 kPa or less.  However, they require a significantly higher pressure to reseat and must be installed only in systems which provide pressures sufficient to ensure full closing of the valve.
  4. Hose outlet vacuum breakers are a specific type of atmospheric vacuum breaker.

Source: Building Industry Authority, November 2004

Typical backflow risk categorisation

In addition, we have provided a list of typical business types in High, Medium, and Low risk categories. This list is not exhaustive and is based on general water usage considerations. Therefore, it may not accurately reflect the actual risk onsite, and risk assessments are required to be done on a case by case basis.


Low Risk: Medium Risk: High Risk
Residential properties (With no pool or spa) Properties with Pools or Spas Properties with plumbed Bidet systems
Retail Stores (Clothing, Electronics, etc.) Auto Repair Shops Commercial Cleaning Services (e.g Laundromat) 
Small Offices (with household amenities) Manufacturing Workshops Restaurants/Bars and Cafes with Commercial Kitchens
Places of Worship Printing Shops Beauty Spas with Specialized Treatments
  Food Preparation Facilities Hair dressers (with hair wash basins)
  Pharmacies Laboratories
  Butchers Dental Clinic
  Bakeries Medical Centre 
  Restaurants/bars and Cafes (without commercial dishwasher) Radiology Studios
  Grocery Stores Funeral Homes
  Fitness Centers Veterinary Clinics
  Florists Pet Grooming Services
  Medium/Large offices (with cafeteria) Childcare Facilities incl. Public/Private Schools 
    Car Wash Facilities
    Radiator repairs
    Pest Control Services
    Manufacturing Plants
    Printing and Publishing Services
    Garden Supply stores

Backflow prevention device testing

Backflow prevention devices are owned and maintained by council. They are tested annually to ensure the device is functioning and will be maintained and serviced as is required.

Backflow prevention surveys

Following the introduction of the Quality Assurance Rules implemented by Central Government Water Service Regulator, (Taumata Arowai) in 2022, we are now required to actively survey all properties that potentially pose a risk to the public water supply network every five years, to ensure the correct backflow prevention devices are in place.

From early 2023 these surveys will be carried out in-person by our qualified assessor.

Each survey will take around 30 minutes, during which we will check the property to assess what activities are conducted and check if the fitted backflow prevention device is suitable. The type of device required depends upon the hazard risk rating assigned to the property.

If the level of protection is not appropriate, we are responsible for ensuring a new device is installed as soon as we practically can. Installation will be managed by council and carried out by council contractors, with the full cost for the device and installation to be invoiced back to the property owner.

As a water supplier, we are legally responsible for protecting the water supply and ensuring that each property complies with the new regulation. This survey programme is important to protect our water quality and public health. 

Commonly asked questions

The Water Services Act 2021 (WSA) introduced clear and stringent requirements for backflow management. The new water services regulator, Taumata Arowai, have introduced a suite of Water Quality Assurance Rules which sets out the requirements relating to the performance of drinking water supplier duties under the Act. These rules provide the minimum requirements drinking water suppliers must comply with to demonstrate they are supplying safe drinking water.

These rules came into effect in early 2023 and will affect the way that council manage backflow prevention assets and processes.

Council must ensure the backflow prevention device at the boundary is appropriate for the level of risk posed by the (activity on the) property. Existing backflow prevention devices that are not adequate could jeopardise the safety of our city’s public water supply network.

The higher the hazard risk rating of potential backflow, the more complex the device that is needed. To ensure the right device is installed for the right risk, a hazard rating of high, medium or low will be assessed by council and you will be advised what device you require.

No. A boundary backflow prevention device must be installed by a council approved contractor. Local plumbing companies are not approved to install these.

If, after a backflow risk survey, you are informed you need a new device, the installation will be organised and carried out by council contractors. The full cost of the device and install will be invoiced back to the property owner.

List of council approved contractors

All properties, including council owned facilities, must have an appropriate backflow prevention device in place. Businesses and industries that pose more risk should consider budgeting for an upgrade however it is the property owner’s responsibility to ensure that an adequate backflow prevention device is installed at the boundary on the water supply connection to protect the public water supply network. Several factors will determine the cost of the installation, such as the size of the connection, the location of the device, and surface conditions at the site of installation.

Council will allow a minimum of four weeks between surveying a property and installing a replacement backflow prevention device with the invoice to follow installation.

We will do our best to provide property owners with an accurate estimate, but some installations will be more difficult, which means we can’t predict the final cost.

We survey all properties that could pose a risk to the public water supply network every five years to ensure the correct backflow prevention device is in place. However, if a high-risk backflow prevention device is currently installed on your property’s water connection at the boundary then you will not be surveyed again. Council annually tests and maintains all backflow prevention devices at the boundary.

The cost will depend upon the device required and the complexity of its installation. Costs can range from $5,000 to more than $10,000. You will be advised of a more accurate approximate cost when/if works are required and better understood. The final amount will be invoiced to you the month after the work has been completed.

Yes, pools pose a potential backflow risk to the public water supply network and require a testable double check backflow prevention device at the property boundary. It is important to take this into consideration when budgeting for a new pool as some pool companies won’t always include it in their quote.

After surveying your property you will receive a call within seven to ten business days and a letter within several weeks.

Once you have had your backflow prevention device installed, it will be vested with council and you don’t have to do anything further. The approved contractor will advise council of the details we need to know. This will be entered into our asset database so that we have a permanent record of it. After installation, council will manage the device and carry out annual testing and maintenance.

Minor maintenance such as the replacement of seals or springs are currently managed and funded by council. In the event that the correct backflow prevention device is installed but has failed its test and is unrepairable, council will install a new one and cover this cost.

Backflow problems can occur inside the home as well. If you are planning any work that changes the plumbing system on your property or in your home, talk to a plumber first. Some people create cross connections without realising that they are putting their own health at risk.

No. This is required by the Water Services Act 2021 (WSA) that introduced clear and stringent requirements for backflow management.

It has been put in place to keep local public water supply networks safe and is not related to the proposed reform or the establishment of new water entities.

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