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Summers in Australia are predicted to get hotter and drier. And with water restrictions a possibility in many parts of the country this season, capturing and saving water – and putting it to good use at home and in your backyard – makes great sense. Collecting rainfall in a water tank is a smart first step in urban areas (and usually essential for regional zones), maximising every drop as well as helping you save money on your water bills. The benefits don’t end at your hip pocket, either – water tanks can help reduce run-off, which in turn protects our stormwater drains and waterways.
Water service professional Julian Fyfe says, while using rainwater for drinking is discouraged, a rainwater tank will more than likely allow you to replace all the mains water you use flushing the toilet and in the laundry. And tank water may just save your garden when the heat is on.
When choosing a new water tank, match supply to your demand, says Julian. “There’s no point getting a 20,000-litre tank if you’re not going to use all that water,” he says. “Think about your climate (the wetter it is, the less you need to store), what you’re planning to use it for and the roof area you’ll be collecting from.”
Figuring out the best-size tank for your property requires a bit of maths. Horticulture and sustainability specialist Adam Woodhams explains, “One millimetre of rain falling on one square metre of roof is one litre of water. You will never collect 100 per cent of fallen rain due to splashing and overrun, but knowing this figure is useful for doing a rough calculation of how much you have the potential to capture.”
Adam then follows with this equation to help choose the right size of water tank. “The maths is simple: annual rainfall for your area, multiplied by roof area to be connected, equals potential annual maximum,” he says. “For example: 1000mm x 50sqm = 50,000L. This means that, even with regular use, a 5,000 or 10,000L tank would provide consistent supply as it would likely be regularly topped up.”
To get the most bang for your buck, Julian suggests you connect the tank to your toilet and laundry. “That way, you have a constant drawdown of the water – you don’t want it just sitting there,” he says. “But if you’re also planning to use it for the garden and you’re in a drier area, then the bigger the tank the better.”
The ideal tank material depends on its use and location. Plastic models come in a variety of shapes, but Julian says steel tanks are more suitable for storing more than 10,000L. Underground water tanks are usually concrete.
Slimline designs and colours can make new water tanks a landscaping asset. However, Julian advises checking with your local council for planning controls, as some may stipulate that the tank must not be visible from the street. Other factors include not placing it under trees and sealing it to prevent animals getting in. “Lower temperatures help inhibit biological growth in the water, so tanks are better placed in the shade,” Julian says.
Consider the weight, too: 1,000 litres of water weighs one tonne. You need to ensure the position of the tank has a level, stable and strong base, such as concrete.
Once you have decided on your rainwater tank, a first flush diverter is an important addition – this sends the ‘first flush’ of rainwater away from your tank, to help prevent debris washing in.
You may also require a pump, says Julian. “If you’ll be watering your garden with a watering can, the pressure will be okay, but you will need a pump if you’re connecting the tank to indoors,” he says.
Julian recommends a pressure vessel (a cylinder that sits over the head of the pump), so when someone turns the tap, the accumulated pressure pushes the water through the tank, so the pump doesn’t have to constantly turn on and off. “This protects the pump and your pipes by reducing ‘water hammer’, and stops your pipes potentially leaking and breaking,” he says.
Plants and soil seem to respond better to natural water than town water, and Adam says there are a few reasons why. The pH of rainwater is likely a better balance – though that can be changed by atmospheric pollution – and it is more likely to contain beneficial elements such as nitrogen, an essential plant nutrient.
Adam explains that a thunderstorm allows atmospheric nitrogen to mix with water and oxygen, turning raindrops into a light, liquid feed. “This is why gardens and lawns often look so lush after a thunderstorm,” he says.
Your rainwater might pick up some less beneficial additions, however. “If you are in a built-up area or an area of high pollution, I would recommend that you have a basic filter attached to your tank to remove potential contaminants like lead, which may otherwise end up concentrated in the soil,” cautions Adam. “Especially if you are growing food plants.”
You’ve done the work to collect all that precious rainwater, now make sure not a single drop is wasted. Adam recommends adding tap timers to all taps, tank or otherwise. “This is a simple way to conserve water,” he says. There are a few options to consider.
Manual tap timer: This low-tech option has a mechanical dial dictating how long the tap will run, automatically switching off the water at the end of that period.
Digital tap timer: A gadget that allows you to control both the duration of watering and when the water runs. This means you can schedule a dawn watering – to maximise absorption and minimise evaporation – without getting out of bed.
Smart tap timer: This is a digital tap timer with more. Connected to an app, it gives you control from anywhere, with greater precision, and can be linked to the local weather service, so your irrigation won’t switch on if rain is forecast. Even better, you can link it to compatible moisture sensors and smart weather stations, for a watering schedule that’s tailored to your garden’s unique needs.
1. Contact your local council and water authority to find out whether you need approval to install a tank on your property. In some jurisdictions, installing a rainwater system may be required when you build or renovate. Government rebates may be available to help you invest.
2. Where a public water supply is available, health authorities generally recommend using it for drinking and cooking, and restricting rainwater strictly to non-drinking uses such as garden irrigation, flushing the toilet and washing clothes.
3. Any plumbing or hardwired electrical work must be carried out by a licensed tradie.
Find more sustainability advice and ideas.
Photo Credit: Alamy
Asbestos, lead-based paints and copper chromium arsenic (CCA) treated timber are health hazards you need to look out for when renovating older homes. These substances can easily be disturbed when renovating and exposure to them can cause a range of life-threatening diseases and conditions including cancer. For information on the dangers of asbestos, lead-based paint and CCA treated timber and tips for dealing with these materials contact your local council's Environmental Health Officer or visit our Health & Safety page.
When following our advice in our D.I.Y. videos, make sure you use all equipment, including PPE, safely by following the manufacturer’s instructions. Check that the equipment is suitable for the task and that PPE fits properly. If you are unsure, hire an expert to do the job or talk to a Bunnings Team Member.
