Where would my greywater and stormwater go?

Water conservation is a very important aspect of my off-grid renovation. A lot of time and effort has gone into developing the right rainwater tank system for my backyard, an appropriate greywater system that will be used to flush toilets, wash laundry and water my garden, and a unique design by Michael Mobbs for a streetgarden outside my house that harvests stormwater and uses it to water plants and a tree.

I was really interested in finding out if I weren’t taking all these steps to collect, use and reuse water at my house, where would it all be going?


1.     When it rains, any water that’s not actively collected or diverted to water plants and gardens runs off roofs, roads and footpaths into a series of city pipes and channels at which point it is called ‘urban stormwater’.

2.     This stormwater wastes no time in picking up all sorts of pollutants such as large pieces of rubbish, fertilisers, animal excrements, heavy metals, petroleum, diesel and any other urban pollutant you can think of.

3.     Stormwater pollution is the single biggest threat to the health of Sydney’s waterways because it flows into them untreated. Some areas will screen and filter out some of the larger pieces of rubbish, but all the pollutants that the water picked up on its journey around the city are dumped straight into Sydney’s harbours.


1.     When wastewater (or sewage) leaves your house, it flows through pipes to a city sewage plant where it is treated.

2.     There are many sewage treatment plants in Sydney that use different processes to clean wastewater, but they all use some combination of: screening out larger pieces of rubbish, using bacteria to break down other contaminants in the water, performing additional filtration and adding chlorine to disinfect the outgoing water.

3.     Many times, stormwater can make its way into the sewerage system which causes it to overflow and discharge directly into creeks and stormwater pipes. Although these surcharge points ensure that the sewerage system does not back up and overflow into private residences, it means that untreated sewage is going straight into the city’s harbours and waterways.

Suffice it to say, my research only further confirmed why I am dedicated to collect, use and reuse as much rainwater as I can as well as harvest the stormwater on my street to help our local trees grow. I am doing my best to reduce the harmful effects that the water would otherwise have on our city’s natural resources.