Believe it or not, rainwater harvesting is the third largest water source in Australia after surface and groundwater. In fact, approximately 1 in 4 Australian homeowners have a rainwater collection tank on their property. For the other 3 out of 4 Australians, we ask, “what are you waiting for?”
In this complete inspirational guide, we will fully explain the most frequently asked questions regarding rainwater collection. We’ll take a look at the benefits, methods, and components of rainwater harvesting, as well as 3 large-scale rainwater harvesting examples to help inspire your future installation.
What is Rainwater Harvesting?
Despite sounding complex, rainwater harvesting is much simpler than most people imagine. Rainwater harvesting can be used to refer to any rain collection system on a property that prevents the water from running off. Most commonly, rainwater is collected on a roof and sent to a large storage container for reuse.
Why Harvest Rainwater?
There are many benefits of harvesting rainwater, some of which are more obvious than others. Today, Aussies typically harvest rainwater for the following reasons:
- Lowered water bills in the home
- Smaller ecological footprint
- Independence from water mains
- Control over water quality in a home
- Provide an ongoing source for clean drinking water
- Easy, automatic garden watering systems
- Reducing the negative impacts of stormwater in the area
In some cases, local government regulations may actually cause rainwater collection to be a necessity, rather than a luxury. This is especially true in some of Australia’s dryer and more arid climates where rainwater collection is entirely necessary to support ongoing water demand in a remote location (looking at you Southern Australia).
Common Issues with Rainwater Harvesting
Despite all of its incredible benefits and potential, there are many issues that arise when installing and operating a rainwater harvesting tank and system in Australia. While conditions and challenges may vary on a case by case basis, the following are some of the most common hurdles for ongoing rainwater harvesting systems:
- An expensive upfront cost for materials and labor
- Combating unpredictable or unreliable rain patterns
- Ongoing upkeep and continuous maintenance
- Potentially harmful chemicals in roof paint and other existing building components
- Adhering to local storage limits and property regulations
- And individual property challenges (i.e. flat roof or limited space for storage)
More often than not, it is easy to overcome challenges and install an effective rainwater collection system. For Australians, there are many local and national resources that help connect property owners with local experts and parts manufacturers to help find ideal, custom solutions.
Different Rainwater Harvesting Methods
All rain falls from the sky, however, continuous industry innovations have led to many different methods for harvesting rainwater on a property. Below, we will outline some of the most common rainwater harvesting methods used by Australian homes and buildings today.
Rooftop Rainwater Harvesting
First, rooftop rainwater harvesting is one the most popular and easiest methods to adopt for Australian rainwater collection. On most buildings, rooftops can serve as a large collection area where raindrops are able to land and be directed into a large storage container.
Rooftop rainwater harvesting systems are made up of 3 components:
- the collection area (the roof)
- a conveyance system (typically gutters)
- and a separate storage container (large barrels or reservoirs)
From the highly complex to the relatively simple, rooftop rainwater harvesting systems can be installed and optimized by contractors and DIY enthusiasts alike.
Surface Runoff Rainwater Harvesting
Next, surface runoff harvesting is another popular method for most collecting rainwater that is especially useful for large properties. Runoff rainwater collection systems are typically much harder to install than rooftop rainwater systems and are usually reserved for professional contractors or new construction properties.
The main difference between surface runoff and rooftop rainwater harvesting is the location of the storage. Surface runoff barrels and wells are usually dug deep into the ground at the lowest elevation point on the property. With this, more infrastructure can be added to direct all of the excess rainwater that hits the property into the in-ground storage.
Due to the increased likelihood of toxic chemicals, surface runoff rainwater harvesting systems are typically only used for irrigation, rather than drinking. It is also necessary to build and install outflow systems so that the water can be easily used on the property nearby.
All-in-one Rainwater Collection Barrels
Lastly, there are also many great all-in-one rainwater harvesting systems that are perfect for first-timers, experimenters, and other small-scale applications. If you are not ready to invest in a full property system, it is possible to purchase one of these small all-in-one systems in order to “dip your toes in the [rain]water.”
All-in-one rainwater barrels can be placed overhangs or even in full-exposed areas of the property in order to collect the falling resources. Once filled, the barrel’s reserve can then be used for easy irrigation or other non-drinking purposes.
The Basic Components of a Rainwater Harvesting System
As we’ve mentioned, rooftop rainwater harvesting systems are by and large the most popular and practical for most Australian properties. Knowing this, we will break down the components of a typical rooftop rainwater harvesting system to showcase how easy and effective they are to install and use.
Image from https://homesteadandchill.com/wp-content/uploads/2019/12/rainwater-collection-system-schematic.jpg
First, the location of a rainwater harvesting system should be scrutinized prior to installation. To minimize upfront material costs, rooftop rainwater collection systems should be stationed as close to the home as possible. All of the components should also be in a location where it is easy to access, as maintenance may be necessary in order for continued use to be possible.
The Catchment / Collection Area
Next, the catchment (or collection) area is one of the most important features of an effective rainwater collection system. Since the dawn of modern building techniques, sloped roofs of various materials have been installed to whisk water away, which works to the advantage of a rainwater collection system.
In short, the larger the roof, the more rainwater it can collect and send into storage. Nearly all roof types are effective, although old roofs with lead-based materials should be replaced or repaired prior to using a rooftop collection system for drinking water in a home.
Conveyance System & Downspout
After hitting the roof, rainwater is then collected in the conveying system and sent through a downspout. Working with gravity, rainwater trickles down the roof and into gutters which are sloped downwards towards the storage container. In most high-quality systems, gutters are covered by a screen to prevent the build-up of dirt and debris.
Screens & Filters
Throughout the collection and distribution process, the rainwater is sent through a series of screens and filters to improve water quality and ensure ongoing system operation. Before entering the storage area, water is typically filtered at least twice: once for the big stuff and a second time to weed out bugs and bits of dirt.
If you plan on drinking the rainwater that you are collecting, then a more advanced water filter is necessary to purify the rain so that it is safe to drink. Although rainwater is typically not very hard, a water softener may also be used within the house to prolong appliance life and minimize damage to tubs, sinks, and more.
Overflow Protection / First Flush Diversion
Next, overflow protection is a critical part of any rainwater harvesting system that is often overlooked by first-time experimenters. No matter how large your barrels are, it is often very surprising just how fast your water storage can fill up to capacity during rain storms.
In order to prevent damage to the tank and the rest of the system, automatic overflow protection is used to divert excess water capacity from entering the storage unit.
Beyond this, overflow protection systems are also usually equipped with a first flush diversion to keep water quality high. For those that are unfamiliar, the initial rainwater that runs off a roof is typically much dirtier than the successive flows. With this, smart systems use a “first flush diverter” in order to reject the initial rainwater to save room for cleaner water to be sent to storage.
As we’ve alluded to several times, storage is perhaps the most critical component of a rainwater harvesting system. Large tanks can be installed above the ground, below the ground, and even bladder tanks can be used in unused spaces, such as below the deck. Tanks can also be linked together for maximum water storage. Rainwater tanks can be made up of a variety of materials including plastic, wood, metal, and more.
Although there is a lot of wiggle room for creative storage solutions, a few things are necessary to keep stored water safe for use on the property. For one, all plastics should be BPA free. Secondly, containers cannot be clear or see-through, because sunlight may cause stored water to grow algae or other system-damaging lifeforms.
Image from https://www.texasvox.org/wp-content/uploads/2014/05/Rainwater-Harvesting-Diagram-by-Vanisle-Water.jpg
Spigots and Outflows
Lastly, your harvested rainwater can only be used with proper spigots and outflows for your water to travel through. Typically, most simple systems have some sort of tap on the exterior of the barrel and room to easily fill a bucket or watering can. Spigots should be installed with some sort of a switch or human control to halt the water from constantly leaking.
In full-residential systems, outflows may be triggered simply by the water controls in your kitchen, bathroom, and laundry area. For landscape watering, it is also common to have a system of pipes installed for even distribution of the collected rainwater.
Considerations for Rainwater Harvesting Systems
The first step to designing a rainwater collection system is evaluating your property’s potential with a full feasibility analysis. In order for a rainwater harvesting system to be effective, the property should receive enough annual rainfall and have ample room for collection and storage. To get started, here are a few things you should determine:
- Your area’s annual rainfall
- And your roof’s surface area (potential to collect rainwater)
By multiplying your estimated annual rainfall (in mm) with your roof’s surface area (in square mm), you can then calculate your maximum expected rainwater collection in litres. Of course, as we mentioned earlier, annual rainfall collection potential should be lowered slightly to account for first flush diversion and tank overflow.
Once you’ve determined your property’s rainwater collection potential, then you can begin to brainstorm the possible uses for your new harvested resource. For small systems, rainwater can be used extremely effectively, even if it never enters the pipes of your home. Simple systems for irrigation and landscape watering can typically be sized to store rainwater all the way through even the driest of dry seasons.
Secondly, if rainwater harvesting will be used in the home, there are essentially 2 different capacities: limited or potable water. Both limited and potable water systems can dramatically reduce main water consumption and costs in your household, with a few different things to consider.
Limited rainwater systems – Limited or “grey water” systems can be used in toilets, laundry, hoses, and more. Although it is not made to be safe for drinking, limited rainwater systems are an eco-friendly way to run water-based appliances in your home without having to install over-the-top expensive filters.
Potable rainwater systems – Potable or “drinking water” systems can be installed so that rainwater can be used in cooking, cleaning, showering, washing food, and more. Although they are more expensive to install upfront, full-home potable rainwater systems allow for a property to be completely “off of the grid.”
Of course, rainwater harvesting systems cost money to purchase and install. Despite being somewhat expensive upfront, rainwater harvesting is designed to lower costs at home by increasing self-reliance. While most expenses are impossible to avoid, there are also a few things that can be done:
- Source material and labor from local sources
- DIY when possible (DIY downspout diverters are one of the easiest)
- Take advantage of local and national green system incentives and rebates
- And purchase high-quality components with long system lifetimes
When calculating a “break-even” period it may be hard to approximate rainwater collection and use against mains water costs. While rainwater is completely free, systems may be able to “pay for themselves” for high-water users over a number of years. Beyond this, rainwater collection systems also increase property value, which may provide financial returns when selling a home or building.
Lastly, it is very important to understand that rainwater collection is an ongoing system, rather than a “set it and forget it” home component. Systems must be installed in such a way that all components are easy to access and monitor. Throughout the first few years of a rainwater harvesting system’s lifespan, owners should pay attention to potential system stop-ups and leaks to prevent further, more costly damage from occurring.
Rainwater Harvesting Case Studies
Alright, before we wrap up, let’s take a look at some real rainwater harvesting case studies from around Australia. Below, we will showcase a few of the most exciting and interactive active rainwater collection systems down under.
Image source: https://upload.wikimedia.org/wikipedia/commons/thumb/b/b1/Ceres_rainwater_tank_1_Pengo.jpg/1024px-Ceres_rainwater_tank_1_Pengo.jpg
CERES Community Environment Park in Melbourne
First, Victorian readers may be well aware of the Centre for Education and Research in Environmental Strategies (CERES) Community Environment Park located in Brunswick East, Melbourne. Throughout the 4.5 acres of the urban greenspace, the CERES Environment Park gives visitors the opportunity to participate in or observe a number of sustainable practices including:
- Beekeeping meetings
- Community gardens
- An organic grocery
- A food nursery
- A cafe
- And more
Most importantly, the CREES Community Environment Park is home to the Urban Water Conservation, Demonstration, and Research Facility which supports many local, sustainable water projects.
In the image above, you can see a large rainwater collection barrel that is attached to the gutter systems of multiple park rooves. Scattered around the park, there are many more barrels of various shapes and sizes. Altogether, the collected water is used to aid in the gardens and facilities, typically being cycled back directly to adjacent buildings.
Image source: https://www.thefifthestate.com.au/wp-content/uploads/2020/01/Marrickville-Library-Day.jpg
The Marrickville Library and Pavilion
Headed north to Sydney, the new Marrickville Library and Pavilion has made headlines as one of the best new purposefully-built structures in Australia’s most populated city. Remodeled from an old hospital, the Marrickville Library incorporates many cutting-edge design elements to reduce energy consumption and function independently.
In the image above, you can see six large rainwater collection barrels installed on the building’s spacious 1,200m² outdoor pavilions and garden. Here, the recycled water is used primarily to keep the low-maintenance plant features alive and well. Beyond rainwater collection, the Marrickville Library also features:
- Natural ventilation & raised flooring
- FSC certified timber and recycled building materials
- Controlled passive solar design
- And more
Open to the public, the Marrickville Library can now officially be added to any eco-tourism vacation to Sydney.
Image source: https://www.solarquotes.com.au/blog/wp-content/uploads/2021/01/la-trobe-sports-solar.jpg
La Trobe University’s Sports Stadium
Lastly, we’d like to head back to Melbourne to feature La Trobe University’s Sports Stadium in the suburb of Bundoora. This massive complex has a “6-star” green energy rating while providing space for an indoor stadium, commercial offices, and educational facilities.
On top of the stadium, the roof is the real MVP (most valuable player) for La Trobe University. The school, which has set a goal for carbon neutrality by 2029, has purposefully designed the roof for maximum sustainability. Here are its key features:
- Sloped and supported by a large rainwater collection system
- 519 kW of installed solar capacity
- And white paint to reflect heat
Although this is by far the largest system on the campus, La Trobe University also supports rainwater harvesting in a few smaller instances nearby. The University also plans to expand sustainability features across its regional branch campuses.
In conclusion, many Australian properties have the opportunity to reduce monthly costs and increase self-sufficiency with an installed rainwater harvesting system. We hope that this guide has helped clear up some of the most commonly sought after information regarding rainwater collection and has perhaps inspired you to begin your own installation.
With rapid adoption across the country, it is now easier than ever to find someone you know that has had their own rainwater harvesting experience to learn about the benefits first-hand. To learn more, feel free to contact us with any of the remaining questions you may have to help you get started.