The home’s water collection system makes capturing and storing fresh water so simple that you wonder why cities need a municipal supply at all.
In fact, households in rural parts of New Zealand have used a similar system for generations. Great Barrier Island, along with much of northern New Zealand, has plentiful rainfall, so there is rarely a shortage of water.
The roofs of the home’s two pavilions were designed to drain rainwater into a channel on top of the central stone wall. This wall conceals twin acrylic downpipes  that funnel the water to a 6,000-gallon concrete tank  that was buried on the site before construction of the home began. Leaf filters collect any debris from neighboring trees before the water enters the tank. The lightless concrete tank prevents bacteria from flourishing and keeps the water cool.
When needed, water gets back to the home with the assistance of a 240-volt pump that’s fueled by electricity from the home’s solar panels. Wastewater is drained to the onsite septic tank , which treats waste with naturally occurring anaerobic bacteria, then releases it to a drainage field consisting of long, slender porous channels buried in the lawn . The hoses allow the waste to seep into the soil to irrigate and fertilize the grass and plants.