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Both the mandatory installation of rainwater tanks and the installation of piping to allow a greywater system in new housing are being considered by the state government as part of its planned 5 Star Plus Stage 2 changes to building regulations.

While the installation of rainwater tanks is quite straightforward (except for what size tanks are required and the additional plumbing costs) a greywater system is more problematic. There are many issues which need to be addressed before these may be permitted by local authorities and the WA Health Department.

Greywater is any water that has already been used in the house, except for toilet water, which is called blackwater. Dish, shower, sink and laundry water comprise a substantial amount of “waste” greywater which can be reused or ‘harvested’ for mainly landscape irrigation.

The main matters that need to be decided if the system is to be accepted and more widely used by the general population are:

• The type of water that can be collected – Kitchen, shower or toilet water?;

• How long this water can be stored in a domestic system without treatment?  Some Australian states do not allow storage of untreated greywater for more than 24 hours due to health/environmental concerns; and

• How this water can be dispersed.  Some Australian states regulate whether greywater can be used only for sub-surface irrigation, or surface irrigation if the water is treated.

All other jurisdictions do not allow greywater to be discharged into drains or waterways.  It must be dispersed within the same allotment.

The State Plumbing Code requires a licensed plumber if an occupant intends to intercept water after it “goes down the plughole”.  The Water Corporation will also need to approve the diversion of water pipes away from the septic system for use in a greywater system.

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