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Backflow Prevention Devices

Tauranga City Council uses the following criteria to determine the level of backflow protection required for boundary protection and the acceptable solution for that risk.  It is an approved document from the Building Industry Authority for Water supplies, G12, Reprinted incorporating Amendments 1, 2 and 3.

Water Supplies Acceptable Solutions
G12/AS1

Table 1: Selection of backflow prevention devices
Paragraph 3.3.1 and 3.3.2

 

Type of hazard

Acceptable devices

Relevant Standard or acceptable solution

High

Any condition, device or practice which, in connection with the potable water supply system, has the potential to cause death.

a)  Autoclaves and sterilisers

b)  Systems containing chemicals such as anti-freeze, anti-corrosion, biocides, or fungicides

c)  Beauty salon and hairdresser's sinks

d)  Boiler, chiller and cooling tower make-up water

e)  Car and factory washing facilities

f)  Chemical dispensers

g)  Chemical injectors

g) Chlorinators

i)  Dental equipment

j)  Direct heat exchangers

k)  Fire sprinkler systems and fire hydrant systems that use toxic or hazardous water

l) Hose taps associated with High hazard situations like mixing of pesticides

m)  Irrigation systems with chemicals

n)  Laboratories

o)  Mortuaries

p)  Pest control equipment

q)  Photography and X-ray machines

r)  Piers and docks

s)  Sewage pumps and sump ejectors

t)  Sluice sinks and bed pan washers

u)  Livestock water supply with added chemicals

v)  Veterinary equipment

Air gap

Reduced pressure zone device
012/ASi Figure 1

AS 2845:Pan 1
Note: The examples given are not an exhaustive list.  Where there is doubt comparison must be made to the hazard definition.

Medium

Any condition, device or practice which, in connection with the potable water supply system, has the potential to injure or endanger health.

a)  Appliances, vehicles or equipment

b)  Auxiliary water supplies such as pumped and non-pumped fire sprinkler secondary water

c)  Deionised water, reverse osmosis units and equipment cooling without chemicals

d)  Fire sprinkler systems and building hydrant systems

e)  Hose taps and fire hose reels associated with Medium hazard

f)  Irrigation systems with underground controllers

g)  Irrigation without chemicals

h)  Livestock water supply without added chemicals

i)  Untreated water storage tanks

j)  Water and steam cleaning

k)  Water for equipment cooling

l)  Drink dispensers with carbonators

m)  Swimming pools, spas and fountains.

Air gap

Reduced pressure zone device

Double check valve
012/ASi Figure 1

AS 2845:Part 1

AS 2845:Part 1
Note:  The examples given are not an exhaustive list.  Where there is doubt comparison must be made to the hazard definitions.

Low

a)  Hose tap used for fixed domestic irrigation systems

b)  Facilities used for the storage or preparation of food and beverages

Air gap

Reduced pressure zone device

Double check valve

Hose connection vacuum break
012/ASi Figure 1

AS 2845:Part 1

AS 2845:Part 1

AS 2845:Part 1

Source:  Building Industry Authority , October 2001

Table 2: Selection of Backflow Protection Paragraph 3.4.5

 

Type of backflow prevention

Cross Connection Hazard

 

HIGH

MEDIUM

LOW

  back -pressure back-siphonage back-pressure back-siphonage back-pressure back-siphonage

Air Gap

(Note 1)

X

X

X

X

X

X

Reduced pressure zone device

X

X

X

X

X

X

Double check valve assembly (Note 2)    

X

X

X

X

Pressure type vacuum breaker(Note 3)  

X

 

X

 

X

Atmospheric vacuum breaker(Note 4)  

X

 

X

 

X

  Note:

  1. Air gaps must not be installed in a toxic environment.
  2. Double check valves can be installed in a medium and low hazard toxic environment.
  3. Pressure type vacuum breakers are designed to vent at 7 kPa or less.  However, they require a significantly higher pressure to reseat and must be installed only in systems which provide pressures sufficient to ensure full closing of the valve.
  4. Hose outlet vacuum breakers are a specific type of atmospheric vacuum breaker.

Source:  Building Industry Authority, November 2004


Last Reviewed: 26/07/2016