Capturing Rainwater in the City

Emma Bowen - Milkwood
Friday, 13th February 2015

Michael Mobbs in Sydney, Australia, harvests his rainwater to not only feed the garden but even to drink! It's that clean!

If you’ve been hanging out in many of Australia’s cities this last week or two, you may have noticed a lot of rain about.

Falling off roofs, gushing down gutters and along stormwater drains, those droplets that sound so glorious on a tin roof are often a lost resource in cities, washing down our hard surfaces and heading out to sea.

Yet there’s the opportunity to capture and store so much of that rainwater in our cities and put it to good use, in our gardens and our homes. In fact it’s rather crazy not to.

After all it’s free, untreated and saves that precious resource being washed down our stormwater drains along with street pollution that eventually ends up in our waterways.

And given that we can expect more water stress in communities in years to come, getting your home set up is a good and darn sensible idea.

There’s been a long-held kneejerk reaction in the past against harvesting water in cities due to pollution concerns, but with careful management and systems built with this in consideration, it’s an easy hurdle to overcome.

As a result many councils around Australian cities are now actively encouraging the installation of rainwater tanks in new and existing homes, with many providing rebates for installation, and some making it a requirement on all new homes.

Last year the Australian Bureau of Statistics said that just over 2.3 million households in Australia used a rainwater tank for their water source – more than a quarter of households, an increase from 19% in 2007.

However in cities, where water is readily available for buying and piping directly into the home, mains water remains the most common option.

The type of system you can get in your home depends on circumstance, what you want to use the water captured for, and of course, space available.

Do you want to capture water simply to water your veggie patch every other day? To use in your laundry and bathroom? Or do you fancy going whole hog and using captured rainwater for everything in your home, including drinking water?

Capture for your garden can be as simple as a small or slim tank with a hose attachment or a tap to fill your watering can.

If your garden’s needs exceed that, or if you’re looking to hook yourself up to something larger that will cover off your laundry and bathroom needs, something like a rainbank with a tank system is great for controlling water supply, by automatically selecting the water source from either mains or harvested rainwater.

Want to provide rainwater for every facet of your urban home and lifestyle? It can be done.

Yes, despite any preconceptions, you can actually capture water in cities to use for drinking water. One man in particular (who you may have heard of) Michael Mobbs has been doing it successfully for decades.


Mobbs, who set his inner city Sydney home up with tanks to harvest rainwater from his roof in 1996, has since been testing the water harvested and found it to be cleaner than the mains water provided in the city.

Mobbs has continued to measure his rainwater consistently over the years.

First testing in 1997 showed that faecal coliform bacteria levels were consistently zero except in the water sampled in June 1997 when the solar panels on the roof were cleaned, potentially causing some disturbance, while turbidity levels (suspended matter in the water) measured well below guidelines too.

Metals in the water when compared to mains water showed much lower levels of arsenic and mercury, and comparable levels of lead.

In his book, Sustainable House, which details his entire experience of setting up a tank, harvesting, testing and using the water, Mobbs says his family overcame the fear of architects, builders bureaucrats, plumbers and the like by researching the facts themselves.

“The water tastes delicious; fresh, sweet and cool from my buried tank, without the chlorine smell or its polluting and harmful by-products,” says Mobbs in his book.

“Get this sweet nectar, taste it, see how ordinary it is, and you’ll wonder at the awfulness of red tape, ‘experts’ and all those who would stand in the way of the citizen drinking it. Killjoys abound. Overcome them.”

Mobbs system overcame any of the potential pollutants that harvesting water in the city may bring with a ‘first flush’ device, which diverts the first 6-10 L of dirty rainwater away before harvesting the following clean rainwater into the tank.

Helping keep the water clean is a sump that excludes the last of any heavy sediment, and self-cleaning gutters that exclude any droppings, leaves and debris from the gutters, but allow water to enter.

All harvested water enters a 10,000 L steel-enforced concrete tank hidden below the house’s back deck – which is generally enough for a family of two, and about all the water their tiny roof can capture.

For any of the above uses – from watering the veggies to drinking – we recommend setting yourself up with the newer stainless steel tanks.

We looked into the options when we were researching water tank options for drinking water for our farm, and found stainless steel to be one of the best options for health and recyclability.

Our latest water tank needs have been urban, however – for supplying irrigation water to the 107 Rooftop Garden in Redfern.

Once again, though, stainless steel tanks were our preferred option – 100% recyclable, no leaching, and they’ll last for many hundreds of years unless you drive a truck over them.

So we recently installed these slimline stainless steel tanks, nearly 1800 L each, at the 107 Rooftop Garden, to harvest roof water for the irrigation of all the food plants on site.

Their slim shape make them perfect for sliding into smaller spots on the site, preventing precious space being wasted – for this reason they’re also perfect for fitting down those skinny spaces next to your house.


Their slimline shape is also perfect for getting them up a stairwell, which was essential in our case.

So take a look at your roof and rainfall this week – is there anywhere you might be able to start harvesting that sweet free water for your home and garden?

This blog post originally appeared here:

Further resources

Watch: Harvesting rainwater in the urban environment

Building a rain garden

Creating Rain Gardens for just £14.99 on our Green Shopping site

Create an Oasis with Greywater


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