You might be wondering what makes stormwater different from rainwater – after all, don’t both come from the sky when it rains? This article will explore what makes one different from the other, clarifying the differences between water harvested as “rainwater” versus “stormwater.”
What is Stormwater?
While it is true that stormwater is generated during a downpour, the technical difference between whether rain is classified as “rainwater” or “stormwater” is where the water hits or ends up.
Stormwater is a form of rainwater that runs over and drains off land during rainfall. This means rain hitting ground surface areas, flowing over yards, down roads and driveways, falling upon gardens, all this rainwater is now considered “stormwater.” This also includes rain falling on rooftops, flowing into gutters and down pipes which spills onto land or is directly fed into a stormwater drain.
In Australia, most properties are connected to a stormwater system consisting of a network of underground pipes. The stormwater system is kept separate from sewer, since unlike sewage which requires treatment, stormwater is generally left untreated when discharged into waterways or out to sea.
What is Rainwater?
While we may understand rainwater in the fuller sense of any water that rains down from the sky, it also has a second very particular understanding when harvesting such water.
Rainwater when harvesting refers only to the rain that falls on the roof, which is to be stored in a rainwater tank prior to contact with the ground. The quality of harvested rainwater is much higher, unlike stormwater which can contain sediments, organic matter, fertilisers, possibly chemicals oil residues from driveways, roads and the like.
Using of Stormwater and Rainwater
One reason for creating a distinction between “rainwater” and “stormwater” is possibly to due to the different applications each have.
Rainwater being a softer water that doesn’t contain sediment or other particles, is better for lathering up soaps, detergents and shampoos. This makes it good for washing clothes, dishes, showers or baths. Provided you have a properly maintained water tank, it can also be safely used in cooking or consumed.
Stormwater however is considered unsafe for human consumption unless treated. It is normally recommended that property owners capture stormwater and use untreated for low-risk purposes such as garden watering and toilet flushing.