Backflow preventers

An automatic backflow device is a specialist valve that prevents backflow from either, back siphonage or back pressure.

A backflow prevention device protects the potable water supply and is required when the potential of a cross connection or hazardous backflow is evident.

An automatic backflow preventer is a mechanical device, just like any other mechanical device automatic backflow preventers are subject to wear and tear, which may render them unable to prevent anything from entering the water main supply.

When a backflow incident occurs, the water drawn back into your main water supply may be contaminated. This contaminated water remains in the water lines until it is drained from another fixture or outlet. A serious health hazard could result when this contaminated water is used for drinking, cooking or bathing there are many documented cases of backflow events, even in New Zealand.

• In 1994 a small town in New Zealand was supplied with drinking water from the local dairy processing facility. Sadly, six people were burned by caustic soda due to a backflow incident affecting the town supply.

Yes, A backflow prevention device may be replaced with an air gap system, the removal of an automatic backflow preventer requires a building consent. A certifying plumber may be able to assist you with this process.

• Air gap systems are not required to be inspected or advised to council through the compliance schedule/building warrant of fitness process.

A backflow preventer is a specified system that is for the protection of potable water from your dosing machine in the dairy shed. There is specific legislation around the addition, maintenance and removal of these devices under the Building Act 2004.

Under G12 of the Building Code, livestock water supply with added chemicals is classed as a high hazard and there are only two types of protection available for the potable water. That is a backflow preventer or an air gap system.

The backflow preventer is a specified system under the Building Act 2004 and therefore is required to be inspected and maintained through your building warrant of fitness system (BWOF).

An air gap system is not required to be inspected or advised to council through the compliance schedule/building warrant of fitness process.

If you are looking to remove a backflow preventer, this must only be undertaken through the building consent process. This is so the application can be assessed to check if the new water protection is suitable. If removing the backflow is approved this will mean the compliance schedule is also removed. This is a requirement under Section 8 of the Building Act 2004

Most dairy sheds have the potable water supply and water for the dosing machine come from the same supply. If the two systems are separated in some way then there should be no requirement for the backflow preventer for the dosing machine. And it can be removed along with the compliance schedule.

A building consent is required to complete this building work.

Below is the requirement for an airgap system from Building Code Clause G12

The short answer is no, Council recommend that you employ a Certified Plumber to design and construct the system that you wish to use and also to remove the backflow preventer and to help with the building consenting process.

Southland District Council has a free 30-minute meeting available for every consent application to help and discuss your project. You can contact us by email building-cs@southlanddc.govt.nz or phone on 0800 732 732.