Backflow Prevention FAQ's

Potable water is water that is suitable for human consumption (water that can be used for drinking or cooking). It is water that is drinkable and safe.

Back-siphonage occurs when there is a decrease in pressure in a potable water supply scheme. Possible situations that can cause this are:

• Large volumes of water being drawn for fire protection.
• Water main breaks or plumbing system breaks.
• A shutdown of a water main or plumbing system for repair.

During a back-siphon event, a reduction in pressure creates a vacuum effect in the pipework and the water flows in the opposite direction. An example of this is if a hose is submerged in a stock trough when the pressure decreases, and the contaminated trough water may be siphoned back into the pipework.

Back-pressure occurs when the pressure in a customer’s plumbing is greater than the pressure in the water supplier’s mains, resulting in a reversal of normal flow direction and allowing possible contamination of the mains water. When there is a reduction of pressure in a Council main pipe, the consumers water pressure only needs to be slightly greater than the public supply pressure to push water back into the public water supply.

Pressure differences between the network and a property can occur when:

• Heavy water use downstream reduces water pressure upstream (e.g. firefighting).
• A water main breaks or is shut off.
• A customer uses water at a higher pressure than the pressure supplied.
• The water outlet at the property is higher than the water main.

All property owners have a responsibility to have adequate backflow prevention in place and/or implement measures to prevent water from backflowing into the potable water supply. This is required under the Clutha District Council Water Services Bylaw 2019.

Council’s responsibility is to protect the public water supply network against the risk of backflow. Council is required to determine when it is necessary for a backflow protection device to be used, maintain a register of the devices, ensure devices are tested at least annually, and have a Drinking Water Safety Plan in place.

This is required under the Water Services Act 2021.

Not necessarily. If you already have a backflow protection device installed at your property, Council will get in touch to arrange a time to assess the device and your property, to ensure the backflow protection meets the required standards.

Initial assessments will begin soon, by way of a desktop survey. Council will determine the listed land use and potential risk factor of all properties within the district.

Following this, Council staff will make contact with every affected property owner to arrange a suitable time for a site audit.

Every water supplier must implement a backflow prevention programme and minimise the backflow risk on a potable water supply under the Drinking Water Quality Assurance Rules 2022. Council is audited against these rules annually by Taumata Arowai, the Water Regulator.

You can read our Clutha District Council Water Services Bylaw 2019 here.

Point of Supply is the point that marks the boundary of responsibility between the property owner and the water supplier, irrespective of the property boundary.

A toby is a water valve, generally located at the boundary of your property. The toby sits between the council water main and your private water pipe.

A water main is the pipe that carries water from the public water source to your property’s service pipe.

A mains break occurs when there is a hole or crack in the water main pipe, causing a leak.

You will be required to install backflow prevention if the findings from your site visit conclude that your property poses a level of risk of backflow. This determination will be based on a number of factors, such as the activity conducted on your property, chemicals or equipment used and stored, or to determine cross contamination risks.

Not necessarily. Every property will be individually assessed to determine their backflow risk level.

If your property is deemed as posing a risk to the potable water supply due to your land use activity, you will be required to have backflow protection. Failing to comply or install protection will be in breach of the Clutha District Council Water Services Bylaw 2019.

If it is assessed that there is a serious risk to the potable water network from your property, and you cannot demonstrate action to manage the risk of backflow, Council may be required to fit a backflow prevention device and recover the cost of installing and testing the device from the property owner.

A backflow prevention device not only protects your drinking water supply from contaminants, but it protects your neighbours and your community.

Reduced Pressure Zone (RPZ) valves and managed air gaps are suitable forms of backflow protection.

Under the Clutha District Council Water Services Bylaw, property owners are required to meet the costs of backflow protection at their property if it is deemed that activities at the site are a risk to the water network.

Council will work with property owners to determine the appropriate backflow protection device for their needs and can assist in arranging an Independently Qualified Person (IQP) to install the device.

Council suggests contacting a local plumber or Independently Qualified Person (IQP) to provide a quote for installation of your backflow prevention device.