Tanks to help cure suburb's floods

Twenty-five North Shore households will host an experiment to see whether rainstorms can be turned into a useful and money-saving source of water.

They live in a part of Glenfield where old drains can't cope with severe cloudbursts and dirty stormwater from sodden properties finds its way via the local creek into the Upper Waitemata Harbour.

After years of complaining about poor drainage, residents were offered an innovative remedy backed by Infrastructure Auckland.

It entails home owners giving up part of their backyards for tanks that can hold 9000 litres of rainwater and make it available for household use.

The tanks will be provided and installed by North Shore City without charge.

The Glencourt Place trial will cost the council $533,000, including earthworks such as building swales, or shallow grassed ditches, to intercept and filter storm runoff before it is slowly released into drains.

Council stormwater manager Roger Hawthorne said it was $100,000 cheaper than upgrading undersized pipes, including a major pipeline.

Trial tanks will serve 45 homes over an area of only 4.6ha, but if they are successful they could play a bigger role in the Auckland region's $2 billion strategy to clean up stormwater before it reaches waterways.

One of the Glenfield residents, Helen Brown, said she was happy to take out the spa pool to make room for the tank.

She hoped the household's $160 water bill could be reduced by using tank water for showers or washing clothes, cars and gardening.

Residents would take over the cost of maintaining the tank and pump after the trial.

Infrastructure Auckland last week said it would pay 17 per cent of the Glenfield trial and has tagged $150 million for regional stormwater projects.

Using rainwater tanks

* About 180,000 litres of rain falls on a 150sq m roof yearly.

* A 9000-litre tank cuts stormwater runoff from a household property by 60 per cent.

* The tank costs $7000 to fit in a home.

* It can save $100 on a household's annual water bill.