What is backflow?
Backflow occurs when water from a customer's property flows backwards into our pipes. This can carry contaminants including dirt, pesticides, chemicals, oils and bacteria that can harm people's health.
Backflow is more likely to occur if there's a drop in mains pressure, such as during a break or under fire-fighting conditions, or if water pressure at the property is higher than at the main, for example if a pump is operating on the site. This may also include bore pump operating.
Contaminants may enter the drinking water supply via cross-connections between two water sources that should be separate, such as a drinking water system and recycled/reuse. Back-siphoning can also be a cause. This is when contaminants can be sucked back into the water supply due to the pressure being less than the atmospheric pressure, for example connected hoses submerged in pools.
What is a backflow prevention device?
Backflow prevention devices can stop water flowing backwards. Device types are installed depending on the potential hazard to be contained and have a high, medium or low hazard rating. Types of backflow prevention devices include air gaps, one-way flow valves, break tanks and pressure vacuum breakers.
As potential hazards arise from customer activity, such as stock watering, property owners are responsible for backflow prevention to stop contaminates entering our water supply. Under the Building Act 2004 and the Health [Drinking Water] Amendment Act 2007, property owners are also responsible for taking all necessary measures on their side of the supply point to stop water flowing backwards into council pipes.
We need backflow protection at the point of supply to protect all our customers, in addition to any building code/or similar requirement for backflow containment at the location of the fixture and/or zone protection. The greater the potential hazard and risk to our water supply, the greater the servicing and testing regime of a backflow prevention device.
Potential low-hazard properties, such as residential households without an on-site bore, need a non-testable backflow prevention containment device. We have been installing non-testable dual-check valves to accommodate the low risk on these properties, as part of our water meter installation and replacement programmes. The installation of dual-check valves will continue until all such properties have devices. Any remaining water connections that are 25mm or larger, unmetered and of high or medium potential hazard will need a separate device. We are identifying these connections and developing a backflow prevention programme, and will work with landowners for timely implementation.
What's happening now?
We are currently out for conusltation on our draft Backflow Prevention Policy.
We’re proposing a new policy to prevent the backflow of water from private properties that may pose a serious risk to the wider public’s health. When cross-contamination occurs this can carry contaminants including dirt, pesticides, chemicals, oils, and bacteria that can seriously harm people's health.
Through the proposed new Policy, we aim to work collaboratively with owners of high to medium risk properties to ensure contaminated water from their activities doesn’t enter the public supply through the installation of backflow prevention devices on their property boundary.
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) these activities pose to our water network.
High/medium risk vs low risk
High to medium risk properties include (but not limited to) farming, industrial and commercial properties, and domestic properties with swimming pool, bore, in-ground irrigation system, and some home-based businesses e.g, salon.
Low risk are those domestic connections (general households).
Only medium and high-risk devices require testing, so in most cases there is no ongoing costs to normal domestic connections.
Our proposal
- All connections to the Council’s water supply network will have a backflow prevention device installed at the boundary to protect the water supply from contamination (this is required in accordance with the law.
- Council will own and be responsible for the devices.
- Domestic connections will generally have a (non-testable) dual-check device.
- Non-domestic connections (farming, commercial and industrial) will have devices that require annual testing to ensure their safe ongoing operation.
- Where testing of devices is required, Council will do the testing and recover costs from property owners.
- Council will undertake testing, maintenance, and replacement of devices.
- Developers are required to install devices in all new developments which will be vested to Council
We have been working on this format for a while and what we are proposing in the draft Policy is consistent with previous decisions which have been made through the Long Term Plan and Fees and Chargers schedule. We are now just formalising the draft Policy to go forth with installing and the fee and charge for maintenance and want to know what people think.