Everything You Need To Know About Rainwater Harvesting

Rainwater harvesting is one of the most effective ways to save water and has many benefits for the both individual and environment.

When done correctly, the process allows users to collect rainwater that falls on roofs, hard surfaces and runs into into gutters and drains (and would otherwise be wasted), and to store it for use later on.

There are many different rainwater harvesting systems, but the process is generally quite simple to setup and maintain, which makes it a popular solution for households, farms and commercial and industrial organisations alike.

If you’re curious about rainwater harvesting and want to get started, below is everything you need to know.


What Is Rainwater Harvesting?

Simply put, rainwater harvesting is a process used for collecting and storing rainwater. It’s a very effective way to make the most of the rainfall and to ensure that less goes to waste.

Just think about the rainwater that falls on roofs, hardstand areas, paths and other impermeable surfaces. Usually, all this precious water would simply run into the stormwater system or the drain away, but rainwater harvesting allows it to be captured and used to supplement or replace reticulated water used in a wide range of applications – both indoor and outdoor. Remember in times of water restrictions, tank water is yours to use as you want. 

In order to do this, the best solution is the installation of a rainwater harvesting system. They generally consist of the following:

  • A conveyance system – gutters and downpipes that channel the water from the collection surface into a rainwater tank
  • Diverters and filters – to keep leaves and other debris out of the storage tank
  • A storage tank – to safely store the water that has been collected.
  • A distribution system – this includes the pumps and pipes used to transport the water from the tank to wherever it will be used.

What Are The Uses Of Collected Rainwater?

Rainwater can be used for a variety of general purposes and can supplement or even replace municipal water supply entirely. Rainwater harvesting is one aspect of creating a self sufficient home.

In some places rainfall that is collected from roofs is deemed non-potable (depending on the location) before it is treated, but there are still plenty of uses for untreated rainwater, for example:

  • Indoor non-potable fixtures (toilets, washing machines, etc.)
  • Irrigation for gardens and lawns
  • Washing vehicles/pets/outdoor areas
  • Refilling fountains and ponds
  • Drinking water for livestock

In Australia, the average family uses between 250,000 – 300,000 litres of water per year, with over 50% flushed down the toilet and used for garden watering.

Using rainwater for these purposes alone would drastically reduce the volume of water each household used and wasted.

It is also possible to use rainwater for drinking and other potable purposes, as long as the water goes through an effective treatment process. Water treatment and filtration systems are easy to source and will allow you to use your rainwater for activities such as:

  • Showering/bathing
  • Washing dishes
  • Cooking
  • Drinking

What Are The Benefits Of Rainwater Harvesting?

There are many factors that make rainwater harvesting so attractive. Some of the reasons include:

  • Rainwater harvesting helps save water that would otherwise be wasted
  • It will help reduce your council and water utilities water bills
  • It alleviates pressure on reticulated water supply
  • Reduces the capacity constraints in stormwater systems
  • It provides additional water supply in times of drought or water restrictions
  • Installing a rainwater harvesting system adds value to property
  • Rainwater is beneficial for plants and gardens as the water is not chlorinated
  • A rainwater harvesting system is inexpensive and easy to maintain


How Much Rain Can Be Collected?

There are three major factors that influence the volume of water you are able to harvest:

  1. The size of the catchment area or roof. For roofs, this is calculated by finding the area of the building and adding the area of the roof’s overhang.
  2. The size of the rainwater tank will determine the volume of water you’re able to store.
  3. The annual rainfall and its distribution over the year.

If you’d like to work out an estimate of how much water you’d be able to capture and store, the following formula can be used to get an estimate:

Harvested water (litres) = catchment area (m2) x rainfall depth (mm)

You can find the precipitation averages for your area on this handy map. Simply click on your state and then hover your mouse over your specific area. You’ll get useful information regarding the number of days rainfall your area receives, the yearly average and the rainfall variability.
For a simple tank size calculation go to: http://www.bushmantanks.com.au/water-tank-calculator

You can also find a helpful article about drainage and how to keep your home safe from moisture damage, whilst harvesting the most efficient amount of rainwater.

Author: H Lindholm