October 1, 2023

Rainwater Harvesting: What You Need to Know

With many of our rivers and water catchments threatened by drought and the ongoing stress of our own withdrawal of water, a major way you can make your home more sustainable is to collect rainwater with a rainwater tank or a rainwater harvesting system.

In this article, we’ll be sharing:


Benefits of Rainwater Harvesting

Installing a rainwater tank is an environmentally friendly way to reduce your water bill and make the most of rainwater around your home and garden – even when water restrictions are enforced. Reducing your reliance on mains water supply can in turn help to:

  • reduce the need for new dams or desalination plants
  • protect environmental flows in rivers
  • reduce costs of operating infrastructure.

By collecting rainwater from your roof, you can use this precious resource to water your garden, wash your clothes and to flush your toilet. By capturing and using the rain that falls on your house, saving it from going down a stormwater drain, most Australian households have the potential to save more than 45,000L each year, not to mention hundreds of dollars!

Opportunities for rainwater collection and use will vary depending on your location. Typically, urban households will have a connection to a water supply but can significantly lower mains water usage by installing a rainwater harvesting system.
On the other hand, the majority of rural households have to source all their water on their property, and rainwater is often the better-quality option for household supply over river, bore or dam water.

What Can Rainwater be Used For?

Rainwater tanks can be used for many outdoor applications such as for the garden and washing the car.

Rainwater can also be used for home grey-water applications such as in your toilet or washing machine, with proper site assessment and following extra requirements depending on your state requirements.

Whilst the mains water supply in Australia and New Zealand remains the most reliable source of quality drinking water, rainwater can also be used for drinking water in rural areas, when collected with a system that meets quality standards and is also well maintained. It is important to remember the risks of drinking contaminated water with harmful microorganisms such as bacteria and parasites from bird or animal droppings. For more information, consult your state or territory health department.

Application and
Required Quality
Clear Odourless Low in dissolved solids No human pathogens, toxins or heavy metals
Garden/Lawn irrigation
Toilet flushing
Clothes washing

Here are some other ideas for using rainwater around your home:

  • Water your garden and lawn
  • Use in sprinkler or irrigation systems
  • Wash your pets
  • Wash your cars
  • Refill ponds or water fountains
  • Top up your pool water
  • Wash outdoor surfaces like driveways and paths
  • Wash windows (from outside)


Rainwater can be used for a variety of applications – including garden and home appliances. For drinking water, extra water quality requirements must be met to prevent risk of contamination.


For direct rainwater tank access, a tap can be installed at the bottom of the rainwater tank. This is the most affordable option and can be used to fill up buckets or attach to a hose for watering the garden.

However, if you plan to connect rainwater to home appliances such as taps or washing machines, you’ll need to consider installing a water pump. A water pump will provide the required pressure to allow water to flow efficiently through pipes and reach home appliances. This method also allows for automatic switching between mains water and rains water, so you can save on your mains water bill when rainwater is available in the tank.

Alternatively, rainwater harvesting systems can also be operated by a gravity-fed system. In this type of system, a water tank sits high up in the property – and the tank releases water through outlets in its base. This type of system operates by gravity and electricity is not always required, making it suitable for an off-grid lifestyle.

If you plan to connect your rainwater tank to taps or other appliances, you’ll need to consider installing a water pump.

How Does a Rains to Mains System Work?

To understand how a simple rain-to-mains water harvesting system works, let’s take a close look at the Waterboy Hydro Switch Rains-to-Mains Changeover Valve. Here is how it works:  

  • Rainwater is collected in a rainwater tank. 
  • This passes through a filter and into a jet pump (alternatively submersible pump can be used which sits inside the tank) 
  • The pump uses a changeover valve to control the flow of water into the dwelling. The controller will switch the pump off according to the water demand from the tap when the tap is switched off.  
  • The changeover valve allows water supply to be automatically switched between harvested rainwater and mains water when there is no more rainwater left in the tank.  
  • Rainwater is then distributed to the required points including toilet, laundry, and garden taps.  

This is the fundamental way that rainwater harvesting systems will work.  

What You Need to Consider

  1. Check the regulations. Tanks up to 10,000L don’t usually require council approval. However, as regulations change, check with your local council or planning authority before you make a choice.
  2. Check the location. You’ll need adequate space and a safe and stable foundation to install a water tank. For above-ground water tanks, you should aim to have as much of your roof as possible available for rainwater catchment, as gutter and drainpipes can collect rain into a water tank. Underground water tanks are also a great discrete option, however you will need to consider the high cost of installation.
  3. Choose the right tank. You’ll need to work out which tank size based on water consumption and size. There are calculators online such as this one by Pristine Water Systems that can help you find the right size. You’ll also need to consider the tank type and shape as well.

Sydney Water provides a great resource on what Sydney residents should consider. Check your local council and state guidelines for rainwater tank installation requirements.


To start harvesting rainwater at your property you will need the following:

  • Collection system: including leaf-shedding rain-head and first flush diverter
  • Supply system: Including a water pump, controller and filter.
  • Appropriate piping

We’ll cover off the supply system in more detail below and include some recommendations on product solutions for these.


Selecting the pump for your needs is important. There are a few important things to consider:

  • The type of pump
  • Required flow rate
  • Required minimum delivery pressure
  • Friction losses due to pipe, filters and controllers
  • The pressure needed to lift the water to the height of the most critical water fixture

A submersible pump can be fitted in the rainwater tank, saving space and emits much less pump noise.

A free-standing pump is often the more affordable option and will be available in a wider range of pumping capacities. However, this type of pump requires weatherproof housing and a protected spot near to the tank. Bromic Waterboy offers a range of Jet Pumps including Pump & Controller Kits in a variety of configurations to suit your rainwater harvesting needs.

Consult with your plumber, pump supplier or hydraulic consultant for help on selecting the right pump.

Pressure Controllers

A rainwater pump pressure controller is used to switch the pump system on and off as required in response to the water flow. The controller is usually mounted on the pump for outdoor uses.

Mains switch-over devices

Some controllers are designed to switch the supply from rainwater to mains water when the rainwater runs out. This type of controller is generally used for supply to toilets, washing machines and other internal uses where a mains water supply is also available. Something like the Waterboy Wizard water changeover controller is suitable for this.


Filters are used to improve water quality and prevent debris that can damage your water pump.


Bromic Waterboy™ pump systems offers complete solutions for rainwater harvesting including submerged pumps and external jet pump options to fulfil the needs of all rainwater harvesting systems, big or small.

The Waterboy™ Pump & Controller Kits are specifically designed as solutions for pain-free installation and are both backed by Bromic’s industry-leading in-field warranty, with our team of skilled technicians standing by should the unthinkable happen.

Bromic Plumbing & Gas