|
Help prevent water supply contamination North Shore City backflow prevention guidelines North Shore City Council aims to provide safe, high quality drinking water to our customers at all times. From time to time a pressure drop in the water supply system may allow water to flow backwards. When this occurs there is a risk of contaminating the water supply. This process is known as ‘backflow’. North Shore City Council is promoting a backflow prevention programme throughout the city. Our aim is to inform all water users of the possibility of water contamination and help prevent backflow by identifying properties that may be at risk and ensuring the necessary steps are taken to protect the water supply. What is backflow? Backflow can occur when the internal water supply pressure in a property is greater than the mains water pressure and water flows backwards along a pipe. There are two main types of backflow: Back Siphonage occurs when a temporary drop in water pressure occurs and water is siphoned into the drinking water pipeline. This may be caused for example 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 filling a swimming pool with a hose. The chlorinated swimming pool water may inadvertently be siphoned into the public water supply system. Back Pressure 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 usually occurs when there is a pump inside the property.
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 prevention device depends on the type of hazard on the premises. The risk of contamination of the water supply is assessed as high, medium or low as shown by the following table:
|
||||||||
| Type of Risk | Examples | Acceptable backflow devices* | ||||||
|---|---|---|---|---|---|---|---|---|
|
High Processes on the property have the potential to cause serious illness or death. |
Hospitals, mortuaries, chemical plants, laboratories, wastewater treatment plants and pumping stations, hair salon wash basins and commercial dishwashers
|
|
||||||
|
|
||||||||
|
Medium
Processes on the property have the potential to cause sickness and endanger health.
|
Commercial laundries, garden irrigation systems, drink dispensers with carbonators and rainwater tanks connect to household plumbing. |
|
||||||
|
|
||||||||
|
Low
Processes on the property have the potential to constitute a nuisance by colour, odour or taste. |
Hose taps for domestic irrigation systems and hose taps used for filling swimming and spa pools. |
|
||||||
|
|
||||||||
|
*Please note that backflow prevention devices must comply with the Standard AS/NZS 2845 Part 1 (1998) and Clause G12 of the New Zealand Building Code. Why, How and Who? Protection of the water supply is required under the Building Act 2004 and the Water Supply Protection Regulations 1961. All properties must have safe and adequate water supply systems. If there is a risk of contamination an approved backflow prevention device is required to isolate it at the source. Where the risk of contamination is high a device may also be required at the property boundary.
A Building Consent is required for any installation, alteration or removal of plumbing work on your property including work on a backflow prevention device
Testing of backflow prevention devices at non-residential properties is required annually to ensure they are operating correctly. This can only be done by an Independent Qualified Person or IQP (also known as Licensed Building Practitioner or LBP). The results of this test are provided to the Council to record the results as part of the Building Warrant of Fitness annual renewal.
Independent Qualified Persons can be either: • Survey IQPs - who are qualified to survey your property for hazards and advise you on what type of device should be installed and where it should be installed, as well as perform tests; or • IQPs - who are only qualified to perform tests on devices. A list of IQPs is available from Council. Installations must be carried out by a craftsman plumber or a licensed plumber working under the supervision of a craftsman plumber. Your IQP may also be a craftsman plumber. |
||||||||
Water
introduction