Custom Size Water Tanks

Steel Water Tanks From 500 to 37,000 Litres



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Thousands of Custom Sizes Available

Different sites have different rainwater harvesting challenges.  Sloping blocks might require a series of water tanks at different heights so they will balance properly.  A low set house on a large property might require squat tanks with a large diameter and low inlet height.  Whatever the challenges Select Water Tanks will help find you the perfect solution.

Slimline Water Tanks

Slimlines are perfect for narrow blocks or yards without a lot of space.  They can fit down the side of a garage or shed without stealing too much real estate.

Select Water Tanks can manufacture down to a minimum width of 550mm for very tight spaces.  It’s important to consider the height of a very slim water tank.  As a general rule, the tank should not be more than 3 times as high as its width.

  • Length Increments:  100mm
  • Width Increments:  50mm
  • Height Increments:  76mm (approx)
  • Common Heights:    1255mm, 1560mm, 1860mm, 2350mm.




Round Water Tanks

If you have the space, a round water tank is by far the best value for money. Round water tanks do not require additional reinforcing, as Slimlines do, so they cost less to manufacture.  They are also easy to clean and maintain.

Select Water Tanks can manufacture a round water tank up to almost 37,000 litres.  Measuring 3900mm in diameter x 3100mm high, this tank requires a crane to position.  Alternatively, we can manufacture a tank that you could fit in the back seat of your car.

  • Diameter Increments: 100mm
  • Height Increments:  76mm (approx)
  • Common Heights:  1255mm, 1560mm,1860mm, 2350mm, 2800mm, 3100mm


How Do I Know What Size Water Tank I Need?

It can be difficult to know just how much water storage capacity you might need for a whole-of-house rainwater harvesting system.  There are several factors to take into consideration:

  • Number of occupants in the household
  • Average rainfall in the area
  • Size of catchment (roof area)
  • Available space on site
  • Budget

Let’s start with a few assumptions:

  • 45,000 litres of total capacity is a good starting point for a whole-of-house rainwater harvesting system
  • A catchment size of 250 square metres
  • The average daily water usage per person is between 150 and 200 litres. Some geographical areas report higher usage.  At the higher end of the scale, a family of four would use approximately 24,000 litres per month.
  • Monthly average rainfall figures for a certain area are widely available on the internet. For this exercise we are researching monthly rainfall in Currumbin Valley, Qld.  These figures are available at

The relationship between the catchment size and rainfall is key to determining the desired capacity of your system;

10mm of rain on 100m2 of catchment will result in 1,000 litres of harvested rainwater

Other factors including evaporation, absorption, first flush diverters, or gutters full of debris are not accounted for in this example.

The table below shows the rainwater harvest yield in Currumbin Valley for the stated assumptions.  It assumes the tanks are not filled with water on installation but by rainfall only.

By July the household is consuming more water than it is harvesting and by October the tanks are reduced to 31% of capacity.


Any change to the variables; number of occupants, catchment size or total capacity, will make a substantial difference.  For example, the table below assumes a 5 person household.  Again, the household is consuming more than it harvests but by a greater amount, resulting in empty tanks by September.  The tanks will remain empty until the following January.

In this case it might be worth considering larger tanks.  The following example represents the assumptions above, including a five person household, but with a total capacity of 60,000 litres.

From this example, it becomes evident that a five person household in Currumbin Valley with a 250 square metre catchment will require a minimum of 60,000 litres of total capacity to see the household through the dry months.


Inlet and Outlet fittings can be located anywhere that is appropriate on the tank and you will be asked to provide us with the best locations when you place an order

Get in touch

Jumbo Stainless Slimline

This customer needed 20,000 litres on a long skinny block in Paddington.

Under The Deck

Under deck tanks are perfect for sloping sites.

Commercial Water Tanks

Water tanks for industry with commercial fittings.

Space Saving

Aquaplate Slimline Water Tanks are perfect for wash bays in high traffic areas.

Need Advice or a Price?

We love talking tanks!

If you need a hand selecting the right water tank, pump or accessories, we are happy to help.

Call Select Water Tanks on 1300 854 231 or click the link below.