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oat seals the diversion pipe once it is full
rst ush diverter pipe
valve releases water slowly and diverter empties to drain
First- ush diverter.
water to tank
Figure 3
position of oat before rainfall
● ifthestoragetankisbelowground,ensurethat surface run-o from areas other than the roof catchment cannot get into the tank.
Leave a new roof for at least one good rainfall before connecting downpipe to the storage tank. A few do nots
Do not use collected water for drinking if it has been in contact with:
● uncoated lead ashings – lead ashings on
existing roofs should be coated with suitable
paint – coated lead is available for new roofs ● treated timber – chemicals leaching out might
contaminate the water
● asbestos – although asbestos is no longer used
in new building work, existing asbestos roofs
should not be used for collecting rainwater
● bitumen, lead-based and other paints that do not meet required water quality standards.
Water catchment system
The water catchment system comprises the roof, gutters, downpipes, water storage tank and the pipework connecting the two.
Downpipes may be open, i.e. they can easily be disconnected if required (such as for roof cleaning or if contamination of water occurs), or sealed if the pipework remains full of water and cannot be easily disconnected.
● install mesh leaf guards over gutters to keep debris out (see Figure 1)
● install leaf screens to downpipes to keep debris out of the storage tank (see Figure 2)
● install a rst- ush diverter to divert the rst
water from the gutter away from the storage
tank (see Figure 3)
● install a system of ner ltration to remove
smaller particles that are not removed by the
leaf guard and screening systems
● if spray drift is anticipated, disconnect the
pipes and do not reconnect them until the roof
has been well washed by rain.
Storage tanks
To reduce contamination in the storage tank:
● install a calmed water inlet system to reduce
sediment disturbance during heavy rainfall
● install the water intake near the water
surface (where the water is likely to be the cleanest quality) using a oating intake (see Figure 4)
● attach insectproof screens or ap valves to the end of all pipes to keep insects out and ensure the tank is vented properly
● install an air gap to the over ow outlet to prevent stormwater back ow into the tank
● keep access covers closed to prevent access
into the tank by insects, pests or debris
Roofing materials
Roofs suitable for water collection for human consumption must meet the requirements of AS/NZS 4020:2005 Testing of products for use in contact with drinking water and may include:
● unpainted zinc/aluminium alloy-coated or galvanised (zinc) steel
● factory-coated or painted zinc/aluminium alloy-coated or galvanised steel
● zinc
● stainless steel
● aluminium
● concrete or clay tiles
● untreated timber shingles – usually imported
western red cedar
● butyl rubber
● asphalt shingles
● bitumen membranes.
Check with the manufacturer.
Tank materials
Tanks and pipework used for storing drinking water, even if only in an emergency, must be made from materials complying with AS/NZS 4020:2005.
Water tanks can be made of galvanised
steel, zincalume (only if not in ground contact), breglass, plastic and concrete. When new, they may sometimes a ect the taste of water. A
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