Rainwater harvesting tanks.

In a drought prone country like Australia, water scarcity is a constant problem, but one of the upsides of being faced with this issue is that Australians are forced to think outside the box when it comes to sourcing water. Rainwater harvesting has long been a way to supplement limited water resources but in recent years, it has seen a surge in popularity as Australian households, farms and businesses seek alternative water sources and self sufficiency. This week, we run through the basics of rainwater harvesting.

Rainwater harvesting tanks.

 

The benefits

Rainwater provide an alternative supply of fresh water during times of water restriction and can significantly reduce a property’s reliance on mains water. By reducing reliance on water mains, rainwater harvesting can also help to protect the health of river as well as reduce the need for manmade water resources such as desalination plants and dams.

 

The cost

Although a proper rainwater harvesting system does require a significant upfront investment, it has minimal running costs aside from servicing and electricity costs associated with a pump. There are also a number of rebates available from both state and local governments around the country.

 

What it can be used for

If the rainwater system is properly designed, installed and maintained, the water it catches can be used for all domestic uses including garden irrigation, toilet flushing, washing, bathing and drinking. The only factor limiting what properly harvested rainwater can be used for is the type of roofing or guttering that the rain has been collected from. Most state health departments recommend using public reticulated water for drinking and cooking as it’s quality is consistent and guaranteed.

 

Components

A typical rainwater system harvests water from your roof and gutters and consists of a collection system, a tank, and a supply system. Gutters need to be fitted with leaf shedding rain heads that catch most of the leaves and debris before they enter the harvesting system. First flush dividers further improve the quality of the water that end up in your tank, by collecting and diverting the first lot of rainwater in a downpour, which will often flush dirt and debris off your roof. Once collected, rainwater can be distributed to the house via a gravity feed, header tank, or pump system. Finally, rainwater filters should be applied to fixtures to remove tannins and sediments.

 

  • A gravity feed is where the rainwater is supplied without external power via a tap at the bottom of the tank. If the tank is 15m higher than the house, the water pressure is high enough for domestic uses such as running appliances and fixtures. Any lower than that, the tank will only be able to be used to fill a bucket, watering can, pool, or be filtered slowly through a garden hose.
  • A header tank uses a low powered pump to transfer water from the main tank to a smaller ‘header’ tank located at roof height allowing the rainwater to be delivered by gravity. Although these systems are energy efficient, they tend to provide only low water pressure.
  • A pressure pump system supplies the rainwater at mains or near mains pressure and are available as a submersible pump or an external pump. The only downside to this option is the noise associated with using the pump, the upfront cost of the device and the ongoing electricity costs.

Types of tank

The size of the tank you need will depend on factors like your intended uses for the rainwater, the rainfall in your area, and the size of your roof. Once this is established, there are several different types of tank you can choose from:

 

Above water tanks

These are the cheapest type of prefabricated tank and are available in the traditional round as well as a slimline design to save space. Larger versions of this tank will need a concrete slab for support.

Storage walls

These are slim plastic tanks that lock together like a wall. Ideal for small spaces, these designs tend to be very expensive.

Underground tanks

These have a much greater catchment potential and don’t take up any space, but have a higher upfront cost as they require excavation as well as a testable backflow prevention device to be fitted on any mains if the water is to be used inside the house.

Bladders

These flexible sacks are ideal for subfloor spaces and can be used to collect from a larger roof catchment than above ground tanks in some situations. They can be installed in spaces with as little as 600mm clearance.

 

Risks

Improperly installed or maintained rainwater tanks can pose a number of health and safety risks such as becoming a mosquito breeding habitat, if the rain contains pathogens or chemicals and is improperly filtered before being consumed, or through backflow.

 

JPG are established plumbers working in Melbourne’s southeast suburbs including Carrum Downs, Kew, Frankston, Dandenong, Berwick and Rowville. To learn more about our capabilities including rainwater system installation, please don’t hesitate to get in touch with us by calling 0400 978 442.