Manukau Drinking Water Quality Programme

Manukau Water Limited has launched a programme to keep Manukau’s drinking water safe from possible backflow contamination.

Backflow is the unwanted reverse flow from a customer’s tap or water system back into the drinking water supply. Backflow can result in a public health risk if water from a polluted source enters the drinking water supply. There have been many instances both in New Zealand and internationally of backflow causing serious health problems and even death.

Manukau Water’s programme will see it audit backflow prevention devices and make sure property owners are aware of their responsibility to install a backflow prevention device at the water meter to prevent contamination.

Manukau Water Limited has identified potentially high-risk customers and will be writing to them, auditing them and visiting them to inform them of any measures they need to take to prevent backflow.

Martin Smith, General Manager of Infrastructure for Manukau Water Limited, said preventing backflow is critical to ensuring the drinking water system remains healthy.

“It is the property owner's responsibility to ensure that the correct backflow device is installed on their property and we will be working with our customers to make sure they understand these obligations,” Mr Smith said.

Mr Smith noted Manukau Water Limited is committed to providing safe, high quality drinking water to our customers at all times.

“As part of this service, we want to ensure backflow does not occur in the public water system,” he said.

www.manukauwater.co.nz

Backflow Facts

What is backflow?

Backflow is a problem that can seriously affect the water supply. Backflow can occur when the water supply pressure at a private property is greater than the mains water pressure in the public water supply system. When this occurs there is a risk of contaminants entering the water supply and there have been cases where backflow has caused serious sickness and even death through contamination of the water supply.

Why does backflow happen?

Backflow can occur when the water supply pressure at a private property is greater than the mains water pressure in the public water supply system and water flows backwards along a private pipe to the public water supply. There are two main types of backflow:

Back Siphonage occurs when a temporary drop in water pressure occurs and water is siphoned into the mains water pipeline e.g. when a contractor is carrying out a repair to a water supply main at the same time as a property owner in the area is refilling a chemical cleansing bath. The chemicals might inadvertently be siphoned into the mains water supply system and contaminate the public water supply.
Backpressure occurs when pressure in the private water supply is greater than the actual mains pressure and water is forced back into the mains water supply system. This can result in contamination of the MWL public water supply and affect the quality of water you receive.
How can backflow be avoided?

A number of simple devices are available that ensure that water can only pass through a pipeline in one direction. The type of backflow device recommended depends on the application of water on site, and what the risk of contamination is assessed to be.

What are the legal requirements for preventing backflow?

Manukau Water Limited is required by the Health (Drinking Water) Amendment Act 2007, to ensure appropriate backflow devices are installed, maintained and tested annually to protect the public water supply and prevent cross contamination. In addition, the Building Act 2004 requires all industrial and commercial properties to have safe and adequate piped water supply systems. If there is a risk of contamination, an approved backflow prevention device is required to be fitted to ensure that all end users are protected against contaminated water.

Who pays for backflow protection?

Property owners are responsible for backflow protection and the costs of this. Manukau Water Limited can undertake the installation or it can be installed to the company’s specifications.