Like anything else, once you've seen one, they are all over the place. We went camping at Innes National Park and the toilets were so... self-sufficient! No electricity, no maintenance; yet a big rainwater tank supplied water to flush and wash hands. What more do you need, really?
I was pleasantly surprised to learn about those marvels - they are green, eco-friendly and incredibly cheap in the long run. Keep in mind that Australia has been having water restrictions for ages - after all, it is known as "the Earth's driest inhabited continent", so they had no choice but to be creative. We just don't think about that stuff back home... we have so much water that we use it to produce electricity!!
My students find this previous statement quite funny; "but... water... ocean..." as they say, pointing out the irony that Australia is surrounded by water, yet many regions suffer from severe drought and bushfires every year. They mean "How come Australians don't desalinate some of that water they are surrounded with?"
Desalination plants are extremely expensive and scarce here - the first one opened in Perth in 2006 for the modest sum of over 600 million$, with a daily capacity of 144 megalitres. There are only 3 of them around Australia. 3 other desalination plants are in progress, and the government is talking about opening a 15 megalitre one in South Australia.
What's interesting here is that many of these plants have included green energy, such as windfarms, in their overall costs. They operate with the use of reverse osmosis.
However, the reason why there aren't more desalination plants around here is that rainwater tanks are much more economical as well as energy-efficient. Indeed, one of those babies is capable of supplying 95% of domestic water use in a typical Melbourne house. A desalination plant would consume 15 times more energy than a rainwater tank to function, and even more to transport that water to the nearest city.
According to a 2007 ACF study:
- Rainwater tanks are 5 times more efficient than desalination plants;
- Rainwater tanks collect and store water far more efficiently than dams;
- If governments deployed rainwater tanks to 5% of households each year in Sydney and South-East Queensland, the need for a desalination plant could be delayed by as much as 16 years.
That being said, rainwater tanks have always been important to supply drinking water in rural and remote parts of Australia, yet only 17% of Australian households own one of them. The number rises to 37% in Adelaide (SA). Nevertheless, it is plenty more than in Canada (it would freeze in winter...) and a great step towards a greener future.
So.
What are they used for? How do they look? How do they work?
Here's a little video of a bloke who has just purchased a 15,000-litre one.
Rainwater tanks are simply connected to the gutter to collect rainwater. Different tanks are used for different purposes. For example, some are just fat containers with a tap on them while others are connected to household pipes (with the use of a pump) for more efficiency. The latter is obviously more expensive to maintain and definitely consumes energy whereas the first type is simple and cheap.
Therefore with one that is connected to the house (like in the video), you can use rainwater to flush the toilet, have a shower, wash the dishes, and so on. Both types of tanks can be used to fill your swimming pool (how much water do they consume!), water your garden, wash your car, even wash your driveway... if you are that kind of person...
Note that people can drink water from the tank but it should be treated or simply boiled first as insects and other particles might have made their way into the gutter.
Rainwater tanks come in different shapes (concrete, plastic, stainless steel, etc.) and size, as well as at different costs. A simple 500-litre tank costs about 450$ while a 15,000-litre one sells for 2000$. I was happy to learn that the Australian government gives rebates to people who purchase one of them in an effort to get the public to take some responsibility for their own water usage.
Do note that this is the price for BASIC water tanks - i.e. with a simple tap. More sophisticated ones, as well as "designer" rainwater tanks (outdoor, underground or even inside the house) with the full installation (pipes, running electrical cables outside, pumps, etc.) can cost you tens of thousands of dollars. My brother-in-law Dave calls this modern "green brainwashing". I'd be happy with a simple stainless steal one.
