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Stormwater

Stormwater is rainwater that falls on the ground, paving, driveways or other hard surfaces within a property. It also includes overflows from tanks and roof guttering. This water can be captured and pumped back for use.

If you want to collect stormwater on your property, you must engage a licensed or registered plumber to undertake this work.

Uses for stormwater

Depending on where the stormwater is collected from, it might be used for:

  • toilet flushing
  • sub-surface and surface irrigation.

Stormwater can carry a wide range of pollutants, including sediments, oils, hydrocarbons and leaves. As a result, it must never be used for human consumption, personal washing, cleaning and cooking. Stormwater should never be mixed with water intended for these purposes.

Your plumber must ensure stormwater cannot contaminate the drinking water supply.

Collecting stormwater

Stormwater should be used only where it has been captured solely from the user’s property. In general, the property must be clean, with no loose soil or chemical contamination (e.g. from petrol or diesel), but this depends on the type of collection used. When designing a stormwater capture, your plumber will consider:

  • collection systems
  • storage options
  • treatment requirements
  • distribution methods
  • the eventual use for the water
  • obtaining necessary approvals.

Using and storing stormwater

As with any recycled or reclaimed water, it is important to match the intended use of stormwater with the quality of the water.

Where possible, stormwater should not be stored in a device that is also used to store rainwater. However, if stormwater and rainwater are stored together, this water must only be used for low-risk purposes such as garden watering and toilet flushing.

Stormwater and greywater should never be stored together. Untreated greywater should not be stored for more than 24 hours as it can turn septic. Stormwater overflow can go back into the stormwater drainage system, while greywater overflow needs to be discharged into the sewerage system.

Treatment

Stormwater should always be treated before use. Generally, the more likely the water is to come into direct human contact, the more treatment and prevention is needed. Stormwater that will be reused for irrigation, for example, may need to be applied through sub-surface drippers rather than surface sprinklers. You cannot use stormwater to irrigate food crops.

Risk of using stormwater

Stormwater can pose the same health risks as sewage effluent. Stormwater quality can vary dramatically depending on where the water is collected, the amount of rainfall and time between rainfall.

Before installing a stormwater system, your plumber should seek advice from the Environmental Protection Authority (EPA) and the Department of Health and Human Services (DHHS).

For more information, see the EPA's webpage on stormwater.