Backflow occurs when water from a customer's property flows backward into the public water supply pipes. This reversal of flow can introduce contaminants such as dirt, pesticides, chemicals, oils, and bacteria, posing significant health risks.
Backflow is more likely to happen under the following conditions:
• A drop in mains pressure: This can occur during events like a water main break or firefighting operations.
• Higher water pressure on a property compared to the public water main: For instance, when an on-site pump, such as a bore pump, is operating.
Contaminants may enter the drinking water supply through cross-connections, where two water sources that should remain separate (e.g. a drinking water system and a bore water system) are improperly connected. Another common cause is back-siphoning, which happens when pressure drops below atmospheric levels, such as when a hose submerged in a pool sucks water back into the system.
Frequently asked questions
- What’s happening?
Following the adoption of Council’s Backflow Prevention Policy, we are ensuring that every property connected to the council’s water supply has the appropriate backflow prevention device to protect drinking water from contamination. To achieve this, we conducted a desktop risk assessment and are now verifying findings through on-site physical surveys before installing the correct device. New Zealand has strict legislation to prevent backflow from occurring and to safeguard the safety of drinking water.
- What’s backflow?
Backflow occurs when water flows backwards into the public water network. This unwanted reverse
flow can cause contaminants, such as harmful bacteria or chemicals, to enter the water supply, seriously affecting the quality and safety of drinking water.- Why is backflow a concern?
Health Risks: Contaminated water can introduce harmful pathogens, chemicals, and toxins into the drinking supply, leading to illnesses such as gastrointestinal infections, skin irritations, or even more severe health conditions.
Water Quality: Backflow can degrade the overall quality of drinking water, causing unpleasant tastes, odours, or discoloration.- What causes backflow?
Water flows to your property under the correct pressure, but if this pressure changes, water could be drawn back into our network. The two main causes of backflow are:
1. A sudden drop in pipe pressure, which siphons water back into the network.
2. If the water supply is directly connected to equipment, such as a boiler or a private bore at a higher pressure, water is forced back into the network.- What is a backflow prevention device?
A backflow prevention device protects the water supply from potential contamination. The type used (e.g. reduced pressure zone, double-check valve) depends on the degree of risk. The device is usually attached to the water meter on the customer side of the point of supply.
- How do I know if my property needs one?
The selection and installation of backflow prevention devices are guided by a risk categorisation system, which evaluates the potential hazard posed by backflow contamination. Risks are categorised into high, medium, and low, based on the potential effects on human health and the environment. Every property connected to the council’s water supply will get a device installed in stages, starting with high-risk properties.
- How is a properties level of risk categorised?
The selection and installation of backflow prevention devices are guided by a risk categorisation system that assesses the potential hazards of contamination. Risks are classified as high, medium, or low, based on their potential impact on human health and the environment. We use a risk matrix to assess contamination risks. If the consequences are significant, we install a device, even if the likelihood is minimal, to mitigate any residual risk.
Risk Categories Defined by NZ Legislation and Standards
High Risk: Situations where backflow could result in severe health effects or significant contamination, such as the introduction of toxic chemicals, pathogens, or other substances that may cause serious illness,
hospitalisation, or widespread public health impacts. Examples include industrial facilities, dairy agricultural
activities, medical laboratories, and properties with chemical storage or processing systems.
Medium Risk: Situations where backflow could result in moderate health effects or contamination, potentially causing minor illnesses or localised impacts on the water supply. Examples include commercial properties, restaurants, or properties with in-ground irrigation systems or swimming pools etc.
Low Risk: Situations where backflow poses minimal risk to health or the environment, with little to no likelihood of contamination. Examples include standard residential homes without additional risk factors.- How many properties require a device?
Approximately 9,000 properties in the Whakatāne District currently do not have adequate backflow
prevention devices. Most of these present a low risk from backflow, so a simple, non-testable device is required.- Where are these devices installed?
The device is usually installed at the property boundary, either in a meter box or above ground in a cage. The type of boundary backflow device required will be determined by the degree of risk from the activities occurring on each property (as defined in the New Zealand Building Code).
- Who owns the devices?
The council will own and be responsible for the devices, including testing, maintenance, and replacement.
- Not a one size fits all…
The type of boundary backflow device required will be determined by the activities happening on each property and the risk (categorised either high, medium, or low). High to medium risk properties include the likes of farming, industrial and commercial properties, and domestic properties with swimming pool, bore, in-ground irrigation system, and some home-based businesses e.g, hair salon. Low risk are those urban domestic connections (general households).
- Is there a cost to me?
Most urban residential properties connected to the Council water supply will have non-testable dual-check valve installed, which does not require annual testing, so there are no ongoing costs to property owners. However, properties classified as medium and high-risk, including rural domestic properties with animals fed through troughs, will require a testable backflow prevention device, which must be tested every year as mandated by NZ legislation. This will incur a yearly fee for testing and/or maintenance if needed. The council will
formalise a process for collecting this payment and will contact affected homeowners.- A device is being installed on my property, what can I expect?
Our contractors may need to talk to you to ensure they’re installing the correct devices for your property’s needs and risk level. There may also be a temporary water shutdown for your property. You’ll receive a written notice at least 48 hours in advance if your property is affected.
- Do new builds require backflow devices?
Yes, developers are required to install backflow prevention devices at their cost in all new developments. This will be included at the building consent stage.
Progress Update
Current Activities
We have now commenced the installation of backflow prevention devices, following a prioritised schedule:
1. High-risk properties: These include farming, industrial, and commercial properties, as well as domestic properties with specific risk factors (e.g. swimming pools, bores, or in-ground irrigation systems).
2. Medium-risk properties: Properties with moderate contamination risks.
3. Low-risk properties: General residential households without additional risk factors.
Key Information for Property Owners
Testing Requirements
Only devices installed on medium and high-risk properties require annual testing to ensure proper functionality and as required by NZ legislations. Testing will be conducted by the Council, with costs recovered from property owners.
Council Responsibilities
The Council will own, test, maintain, and replace all boundary backflow prevention devices.
Domestic Connections
Most residential connections will have non-testable dual-check devices installed, requiring no ongoing costs for homeowners.
Developments
Developers are required to install backflow prevention devices in all new developments, which will be vested to the Council.
Commitment to Public Safety
The installation of backflow prevention devices is part of our commitment to protecting the public water supply and ensuring compliance with relevant laws and regulations. These measures are critical to maintaining a safe and reliable drinking water system for all our customers.