Water Tanks for Stormwater Detention

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Storm Raining on Roof
Source: Rain On Thassos, Edal Anton Lefterov

If you live in and around the suburbs of Adelaide then when building a new house or performing significant additions to an existing house, your council may have stormwater detention requirements that you need to meet.

Why is Stormwater Detention Required?

During storms and a heavy downpour of rain a lot of stormwater can be generated increasing the risks of floods in different areas. This is worsened by increasing residential densities and expanding industrial and commercial buildings that increase pressure on existing underground drainage infrastructure.

Many councils deem increasing the capacity of existing drainage to cater to increase stormwater flows as being infeasible due to space and cost constraints. So the burden is then placed on new home owners to shoulder some responsibility for their stormwater runoff.

How is Stormwater Detained?

Obviously, to detain stormwater means having something to store all the water in. Rainwater tanks present the ideal solution, especially since they are normally a council requirement for new homes.

While traditional rainwater tanks retain stormwater for domestic use, a stormwater detention tank is intended to remain empty except during periods of rainfall and for a short time thereafter. So detention tanks are fitted with a special value that will slowly release water into your stormwater drains over time.

This helps to “detain” or slow the release of stormwater from your property and prevent flooding.

Do I Need To Detain Stormwater?

Whether you need to detain stormwater and to what extent is a question your local council can answer. Your builder should also be able to inform you.

The capacity you need to store answer often depends upon the size of your property and surface area of your roof and building structures on your property. Requirements can also differ from residential to commercial properties.

Councils normally provide some table or equation, but consult your builder. Team Poly can also examine your building plans and provide a detention system to maximise your rainwater use.

Using Rainwater in a Detention Tank

Since stormwater detention tanks only work effectively if they are empty during heavy rain periods, councils dislike detention tanks being used as a water supply for your home.

So you will either require separate tanks – one to collect rainwater for your own use, and another for detention – or a dual use retention/detention system. The benefit of a retention/detention system is the ability to maximise your rainwater collection as your retention tank is filled first and the overflow goes into the detention tank.

These systems often need to be designed for the site and submitted to your council for approval, but the practical benefits are obvious. If you would like advice on a suitable stormwater detention system for your new home, contact the staff here at Team Poly today.