Water

Designing homes to use water efficiently, reduce costs and cope with more frequent droughts or storms.

Rainwater Systems: Specifying Materials

Some roofing, spouting and downpipe materials are not considered suitable for rainwater collection.

As well as choosing appropriate materials, you’ll need to consider other methods of minimising contamination of rainwater supplies and minimising cross-contamination of piped water supplies.

Roof materials

Roofs suitable for water collection for human consumption include:

  • unpainted zinc/aluminium coated or galvanised steel
  • factory-coated or painted zinc/aluminium alloy-coated or galvanised steel
  • zinc
  • stainless steel
  • aluminium
  • concrete or terracotta (clay) tiles
  • copper
  • PVC (without lead stabilisers) or fibreglass sheet
  • untreated timber shingles (usually imported western red cedar).

Lead flashings must be avoided on new roofs and those on existing roofs should be coated with a suitable paint.

Asbestos is no longer used in building materials. Existing asbestos roofs should not be used for collection of rainwater.

Do not collect rainwater for drinking from roofs where the water might be contaminated by chemicals leaching from treated timber.

All collected water used for drinking should be periodically tested for quality.

All new roofs should be left for at lease one good rainfall period before connecting the downpipes to the storage system.

Roof paint and coating systems

Specify only paint that the manufacturer recommends as suitable for collection of rainwater for drinking. Do not collect rainwater from roofs coated with:

  • lead-based paints
  • bitumen-based paints
  • acrylic paint until it has been washed by a good rainfall.

Gutters and downpipes

Suitable materials where potable water is being collected include:

  • extruded PVC
  • factory-coated zinc/aluminium alloy-coated steel
  • galvanised steel
  • copper (may cause staining if water has a low pH)
  • aluminium
  • polyethylene/polypropylene.

Tanks

Suitable materials include:

  • galvanised steel
  • fibreglass
  • plastics such as polypropylene
  • concrete
  • ferro-cement.

Construction and materials should comply with AS/NZS 4020 Testing of products for use in contact with drinking water.

Tank materials should not transmit light, as light will encourage organic growth.

Pipework

Pipes used for potable water reticulation must comply with AS/NZS 4020 Testing of products for use in contact with drinking water.