When building a new home there might be local regulations that require you to detain stormwater. In a related article, we explored stormwater detention and why it is done. This article will help you to work out whether you need to detain stormwater and provide general requirements for new homes.
Do You Need to Detain Stormwater?
Whether you need to detain stormwater and to what extent depends upon the location of your property. If your property is in an area prone to flooding during downpours, then you will likely need to detain water to help with managing stormwater runoff in your area.
Sometimes stormwater detention requirements need to be met when simply installing a rainwater tank. So, prior to having your tank installed it is a good idea to know exactly what is required of your property location.
To find out whether you need to detain water, you should contact your local council. Your builder should also know council requirements and be able to inform you.
Stormwater Detention Requirements
When it comes to detaining stormwater in your tank, and by this we mean storing water runoff which is slowly released into your stormwater drainage, there will obviously be a certain amount of water you are required to detain.
Councils normally provide a table outlining detention requirements, or an formula of some sort. The amount of stormwater detention required will vary based upon different factors. While council requirements differ, they normally they factor in:
- Development type – commercial or residential development
- Property size – the surface space of your property and specific areas required to detain stormwater (for example, dwellings proposed on allotments under 500m2)
- Roof of hard surface area – the area of hard surfaces on your property, normally can only be up to a certain percentage. Since rainwater obviously can’t penetrate hard surfaces, so such can cause problems in very built up area with insufficient drainage.
- Minimum percentage of roof area – to be directed to your detention system and/or maximum outflow (for example, a minimum of 60% of your roof area is directed to your stormwater detention system with a maximum outflow rate of 3 litres per second).
Additional detention requirements sometimes exists for developments that have many hard surfaces such as shared driveways and large parking areas.
To provide an example of stormwater detention requirements, Campbelltown City Council state:
Council’s stormwater detention requirements apply to dwellings proposed on allotments under 500 square metres in area.
Each dwelling must detain a minimum of 2000 litres (2 cubic metres) of stormwater from the roof area of each dwelling. A minimum of 60% of the roof area of each dwelling must be directed through the detention system, with a maximum outflow rate of 3 litres per second.
In developments with large amounts of hard surfaces (such as shared driveways and parking areas), additional detention for those surfaces may also be required.
It is important to know your local council’s specific stormwater detention requirements so that whoever is doing your structural drawings can account for it.
If you need a water storage tank fitted for harvesting water or stormwater detention, talk to our expert team at Clark Tanks.