Beginner’s Guide to Getting Started with Rainwater Tanks!
A home improvement project that I’ve always had on my list is installing rainwater tanks in our backyard. When I was living at home, my parents almost never used tap water to irrigate the garden, and always relied on their two 5000L rainwater tanks to look after the garden. Using water from the tap felt wasteful on the garden, when so much rainwater could be collected and used in just the same way. Rainwater tanks always made sense to me and is something every household should definitely look into. Connect them to your roof and they’ll capture all the water run off from rooftops that would normally go down the stormwater pipe. This free water can then be used to irrigate your garden, or even connected to your toilet to be used for toilet flushing. And by using rainwater, you help preserve a valuable natural resource, save money on water bills and also be more self-sufficient!
In partnership with Bunnings
how to calculate how much rain you can collect (ARE MISSING OUT ON COLLECTING!)
To get an idea of just how much ‘free’ water an average home lets drain away, use the equation below:
Annual Rainfall (mm) x Roof surface area (m2)
To calculate annual rainfall, use this Bureau of Meteorology link. Select ‘Rainfall - Monthly’, enter your suburb and select the matching town, then select the nearest Bureau station to you. Here you will see the annual rainfall for every single year the station has collected data for. Pretty cool huh! You can just take an average from the last 10 years to use for your reference.
To calculate roof surface area. Simply calculate the area of your house by measuring the length/width of your house. While not entirely accurate, this will give you a good enough, rough figure to work from.
For example, say the annual rainfall in Melbourne is 650 mm. And your roof surface area is 180 m2 (an average-ish 3 bedroom home size). Such a house has a potential to collect up to 117,000 litres of water every year. That’s a lot of free rainwater, so let’s get to collecting some of it!
Rainwater tank sizes
When shopping for a rainwater tank, the first thing you’ll need to determine is what size water tanks to get. Common rainwater tank sizes for suburban areas range between 2000-5000 litres, however you can also get very small ones 500L in size. Larger tanks 10,000-20,000 litres also exist, however these are more likely used on rural properties as they take up a lot of space.
While it’s a good idea to calculate how much rainwater you can collect and how much you plan to use, in order to help determine what tank size to buy, I personally think that you’ll unlikely end up with too much water tank storage in a suburban home to collect all the rainwater you can fit. So for the most part, go for as large as you can fit.
A few notes to help you decide though:
A 3000L water tank is a pretty average medium sized tank for a suburban home. Often, people will fit 2 of these side by side, to collect 6000L total.
A 5000L water tank would be a large-ish size for a suburban residential home.
A 1000L water tank would be a pretty small size.
It’s definitely possible to fit 10,000L (2 x 5000L) of water tanks in a suburban residential home if you have space for it.
It’s common to purchase multiple smaller sized tanks in order to fit them on the property, rather than one big tank. E.g. 2x2500 litre tanks, instead of 1x5000 litre tank.
You can always start with one tank, and add another later.
Remember, rain doesn’t always fall consistently throughout the year. So sometimes your tank will be consistently full if there’s a wet period of weather.
Note: if you are doing a new build, you can also purchase bladder tanks (which go underneath the house) or even bury them. However this post is about rainwater tanks that are placed above ground in the yard.
Slimline tanks vs round tanks
You’ll often find water tanks in two kinds of shapes: skinny slimline ones or round ones. Round tanks are usually cheaper to purchase but harder to squeeze onto your property due to their bigger size. They’re often more commonly used on rural properties where space isn’t a problem.
If you’re on a more suburban sized block like me, check out slimline tank ranges which are tanks that are made to fit down narrow walkways on the side of your house. Slimline tanks can be as narrow as 60cm in width, giving you more options on where you can squeeze in a water tank. If you only have space for slimline tanks, consider purchasing a few and connecting them to each other.
Water tank materials
Rainwater tanks come in a range of different materials. Plastic rainwater tanks are usually the more common type and are available in a range of colours and sizes. Metal storage tanks are usually more expensive but last longer than plastics.
Water tank colours
When selecting rainwater colours, darker colours will of course retain more heat causing water to become warm. Lighter colours reflect the heat and keeps the water a cooler temperature. If you are placing it in the shade then this won’t mater so much. You can also choose based on where you are placing it, so matching your wall colour, etc. to help it camouflage. However of course, you can also camouflage using e.g. plants and vines.
OUR WATER TANKS
We were initially going to install one tank at a time based on our budget, but realised that it would be easier to get multiple done together. Based on the space available, we determined that we were able to fit 2x 3000L tanks side by side, so opted for 2x Kingspan 3000L Modline tanks which fit our space best. These were easy to order through Bunnings through the Special Orders desk. When you place your order, you can choose what colour you’d like them in as well as the position of your outlets to suit what you need. The were then made to order.
Where to place your rainwater tanks
As water tanks are quite large visually, most people prefer to place it somewhere that is out of the way and hidden from view. Some councils require tanks to be hidden from street view so double check with your local council to see if they have any rules. It’s common to have rainwater tanks down the narrow side of houses, or at the back in the yard. This can be either next to the wall of your house, or against the fence.
When selecting the site for your water tank, make sure the path to the water tank is accessible, in that it is logistically possible to place the water tank in the position you have chosen. Of course you could get a crane arranged to drop your tank into place if it’s inaccessible, but this is probably a costly and impractical exercise!
Make sure to also check where your down pipes are, as you will need to connect your down pipes to your tank.
how to prepare the water tank base
The first thing you should do when preparing your water tank installation is to prepare the base that the water tank will sit on. Water tanks, when filled, are extremely heavy (a 3000 litre water tank basically contains 3 tonnes of water!) so it’s important to prepare a stable base for it. Common water tank bases include concrete slabs and crusher dust with concrete pavers. Most water tank companies will provide information on what type of base is needed and provide clear instructions on how to prepare it. Once the base is prepared, the tank can usually be delivered right onto your base.
We used concrete for our water tank bases and purchased it from a local concrete supplier. They call it mini-mix concrete which is pre-mixed concrete that they deliver to you. Once the truck comes, you have to get ready to move it on the spot to your site, so be prepared with wheelbarrows and muscles! Alternatively, you can also buy bags of concrete from Bunnings and mix them yourself.
how to install the water tank
Once the tank is delivered in position, you will need to connect it up to your roof. This can be done by connecting the gutter / your down pipe to the water tank using pipe. And connecting the overflow outlet on your water tank back to the storm water drain. So it’s like diverting the water from your gutter into your tank, but any extra water that doesn’t fit in your tank is directed back to your drain.
If you are only using the water tank for garden needs, you can do the installation yourself. If you are also connecting your water tank to mains water (toilet, laundry), then you will need a licensed plumber to do this installation for you.
I hope this guide helps anyone thinking of installing water tanks get a good overall look on how this can be done!