Stormwater Detention and RetentionTanks

Most Greater Auckland local authorities are now insisting on the installation of stormwater detention and retention tanks in all new houses to control the flow of stormwater runoff.

A Detention tank is one that only slows the flow of stormwater.The storm water comes into the tank through a 100ml inlet and then 'dribbles' out through a small aperture in the bottom of the tank.

A Retention tank is a tank where the stormwater is 'retained' in the tank so that it can be used for household use, the overflow is then run off to the council stormwater system. A retention system would pay for itself in cost savings between 1-3 years. See Water Rates Hike article below.

A Detention/Retention tank is a combination of both these types of system

They come in all shapes and sizes, from 4000L through to 27,000L

Download tank Detention Tank diagram PDF
Download tank Retention Tank diagram PDF
Download tank Detention Retention Tank diagram PDF
Download tank Detention Retention Tank - 9 different sizes PDF

The following snippets have been taken out of the NZ Herald 28 May 2007: