What Size Water Tank Do I Need?

by Oct 4, 2022Help & Advice, Select News, Statistics & Data

Wondering “what sized water tank do I need”? It’s a good question, because the answers vary depending on how much water you use! Obviously, the bigger your water tank is, the more water you can store in it. Some of the things you should keep in mind when decided how big your rainwater tank should be include

How Much Water Do You Need?

Rain Catchment Calculator

How Much Rainwater Can You Harvest? Use our rain catchment calculator to find out

Water Tank Dimensions and Sizes

Depending on the space available, and your personal preferences, you can choose whether to order a round or slimline water tank(s). Round water tanks are a common sight across Australia, particularly in regional areas, while slimline water tanks are popping up more and more in urban Aussie backyards and are loved for their space-saving, sleek design.

Slimline Water Tanks

Slimline Water Tanks are ideal for where you have limited space (under eaves, for example) making this water tank design particularly well-suited to urban areas with smaller backyards. They’re also widely considered a more aesthetic choice.

However, there is a caveat: the maximum water storage for a single slimline water tank is 8,500 litres. Fortunately, there’s a way around this – just link up multiple tanks side by side to increase water storage capacity.

Slimline Water Tank Sizing Image 500x412px

Please note: not all dimension combinations are available

Slimline Water Tank Dimensions & Examples of Sizes | Capacities

The right size water tank for you will depend on the rainwater storage capacity you need, as well as the space you have available. For a full list of all our Slimline Water Tank Sizes & Dimensions visit our Steel Water Tank Pricing Page.

Capacity (litres) Width x Length x Height (mm)  
1,583 700 x 1600 x 1560
2,090 650 x 2200 x 1560
2,145 850 x 1800 x 1560
3,065 850 x 2100 x 1880
3,206 850 x 2600 x 1560
3,251 650 x 2800 x 1880
3,322 750 x 3000 x 1560
5,067 700 x 4000 x 1880
5,088 1150 x 2600 x 1880
5,119 1150 x 3100 x 1560
5,352 950 x 3200 x 1880
7,712 1150 x 3100 x 2350
8,523 1150 x 3400 x 2350

Round Water Tanks

Round water tanks can store up to 30,000 litres of water and are ideal where you have plenty of space and where you want a large volume of water – they’re a regular sight in country towns, where they’re helping farmers to combat drought, and significantly reducing the load on mains water supply in regional areas. But if you’ve got a large-enough backyard, they’re a great choice for urban and suburban homes as well!

Round Water Tank Sizing Image 550x412px

Please note: not all dimension combinations are available

Round Water Tank Dimensions & Examples of Sizes | Capacities

The right size water tank for you will depend on the rainwater storage capacity you need, as well as the space you have available. For a full list of all our Round Water Tank Sizes & Dimensions visit our Steel Water Tank Pricing Page.

Capacity (litres) Diameter x Height (mm)  
2,071 1300 x 1560
3,120 1300 x 2350
3,138 1600 x 1560
3,324 1500 x 1880
4,903 2000 x 1560
5,332 1900 x 1880
5,336 1700 x 2350
7,814 2300 x 1880
10,308 2900 x 1560
10,635 2400 x 2350
10,768 2700 x 1880
15,015 3500 x 1560
15,126 3200 x 1880
15,528 2900 x 2350
18,095 3500 x 1880
20,108 3300 x 2350
20,484 2900 x 3100
22,619 3500 x 2350
23,407 3100 x 3100
24,942 3200 x 3100
25,278 3700 x 3350
29,838 3500 x 3100

One Big Tank or Several Smaller Ones Linked Together?

It’s easier to transport and place smaller tanks, and we can place them in different locations to capture rainwater from different aspects or sides of a roof (or multiple roofs). One large tank will take up less space, but it can also mean that you can only capture the water from one roof location, limiting your harvesting capabilities.

From our many years of experience in supplying and installing water tanks, we have found that having three round tanks holding 29,000 litres each (total 87,000 litres) will easily keep even a large family in water all year round.

Can You Use Rainwater Tanks For All Your Water Needs?

80% of households with rainwater tanks consider the volume of water they collect in their tanks to be sufficient for all their needs, including:

  • Drinking water
  • Garden watering
  • Toilet flushing
  • Laundry usage
  • Replenishing domestic pools or spas
  • Car washing
  • Supplying the hot water system
  • Thermal buffers to insulate houses
  • Ventilation for buildings
  • Protecting homes from bushfires

Rainwater that you collect from a well-designed and operated system can be suitable for any and all domestic water uses. For example, you can use you tank water for your garden and some indoor uses (toilet flushing & showering), while still sourcing your drinking water from your water supply. And if you want to reduce your reliance on mains water even further, check out our Rainwater Tank Filter System which can make your tank water 100% safe for drinking as well.

How Much Can You Save?

Harvesting rainwater can reduce your water bills, while taking the pressure off main water supplies. With Australia facing a freshwater crisis, water rates are more than likely to go up in future years, but even at current rates getting a good-quality water tank that lasts for decades means serious long-term savings for you and your family. Below is a guide to the money that you can potentially save by reducing your water bill with a water tank.
Household Size Average Per year
1 $884
2 $1,072
3 $1,248
4 $1,292
5 $1,488

So, What About The Upfront Cost Of A Water Tank?

Is a water tank a good investment? How long does it take to pay your water tank back? All good questions. With around half of Brisbane homes having a water tank nowadays, water tanks are a trend that’s really caught on. And it’s not just about the environmental impact; they’re actually a great buy.

Let’s say that you spend $4,296 on a 3500 x 1560 round water tank with a 15,015L capacity (sounds oddly specific? That’s because it’s an actual water tank we sell – head to our pricing page). If you use 15,000L per month for 3 people, and you save $1,248 per year, your water tank will pay for itself in less than four years – and with a 30-year warranty, you can expect another 21 years of savings. #betterthanbitcoin? We think so!

What Is The Best Water Tank To Buy?

You’re already asking yourself the question “What size water tank do I need?”, but size isn’t the only factor to think about. Cost is another important factor, but remember, there’s a trade-off – a water tank made of cheaper materials like poly (i.e. plastic) will degrade faster and so has a shorter lifespan, whereas for a bit of a higher upfront cost, you can choose a steel water tank with a 30-warranty and enjoy substantial savings on your water bills for years to come.

Other than the materials, the shape of a water tank will affect the pricing – slimline water tanks will generally be more expensive than a round water tank of equivalent sized. That’s because unlike round water tanks, slimline water tanks require internal reinforcing rods to keep their sides stable when the tank is full of water. This makes these water tanks slightly more expensive, but on the other hand, they do have the advantage that they can be fitted into narrow spaces.

For more information check out our article: Best materials for water tanks