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Department of Infrastructure and Planning
Automatic switching device
An automatic switching device (figure 2) controls the water supply to the plumbing outlets by
automatically switching from tank water to mains water when the water level in the rainwater
tank is insufficient to meet household demand. It should switch to the mains water supply at a
level of 1000 litres. The switching device must incorporate a built-in backflow prevention
device to protect the quality of the mains water supply. When an automatic switching device is
installed, a dual check valve must also be fitted at the property boundary. This is necessary to
prevent backflow in accordance with the Act.
to outdoor use
rainwater tank
Automatic
switching device
(dual check valve
built in)
sensor
to approved
rainwater uses
pump
reticulated
town water
supply
to reticulated town
water uses
water
metre
backflow
prevention
device
Figure 2. Automatic switching device plumbing
1.6 Outdoor water restrictions
When an automatic switching device is fitted to the household water-supply system and the
external or garden take off is located on the tank or between the tank and the automatic
switching device, the use of tank water for outdoor purposes is exempt from a council’s
outdoor restrictions.
In all other cases (including with trickle top-up systems) a council’s outdoor water restrictions
apply (see Figure 3)
Potentially mains water
Switching
Valve
X
9
Rainwater
Tank
r
wate
Rain
only
Switching
Valve
Rainwater
Tank
X
9
NOT Restriction Safe
Restriction Safe
Figure 3. Outdoor water restriction
1.7 Overflow from rainwater tank
The placement of a rainwater tank and its overflows must be designed to ensure stormwater
does not:
• pond under building floors
• flood around foundations and footings of buildings
• cause nuisance to neighbours.
Water saving targets For plumbers, builders and developers
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