How Big Should Your Yard Need to Be Fit A Water Tank?

With Australia statistically receiving under 600mm of annual rainfall (many areas receive half that amount), tanks are an essential part of Aussie living. Many modern Aussie pools are built with a rainwater tank beneath them, for convenient conservation and quick refills. And in a way, this answers the question – any size yard can host a water tank.

On a broader level, plastic water tanks can be as small as 100 litres so that you can squeeze them into pretty small yards, concrete tanks, on the other hand, start at about 3,800 litres and can go all the way to 11,500 litres, depending on your tank brand. (Some reach 34,000 litres). This type of tank can be installed underground. They’re sturdy enough to lie beneath a driveway without collapsing. Their covers are infused with stainless steel so they can support the weight of a car.

For this reason, your tank size selection is less about yard size and more about family usage. You want a tank that can hold at least a month’s supply of water. There are lots of water calculators online. They can help you generate a guesstimate of how much water you need. These metrics can be per person or function. For example, if you shower for 8 minutes, you use up about 80 litres of water, while washing your car takes roughly 200 litres.

Tank location

If your yard is on the smaller side and you opt for the in-ground water tank, think about your home’s foundation. You can put a storm-water tank beneath the house, but not a tank for household usage. Refill tanks can go under the pool too, and these often double as detention tanks. Again, this water isn’t for domestic use. It can be fed into the pool because it will be sterilised for external exposure. It’s not safe for cooking, drinking, or laundering.

Water tanks that are certified for use inside the house have to be carefully poured, allowing a foundation f 15cm to 30cm between the tank and the ground. This foundation can be loose sand or poured concrete. Either way, the surface needs to be flat and even. Otherwise – especially with plastic tanks – the slightest stone can perforate the tank. And because it’s underground, you might not spot the hole until all the water has drained out.

This may seem odd, especially because the stones aren’t particularly jagged. But the weight of several tons of water plus the packed earth above the tank can turn the tiniest bit of gravel into a sharp cutting tool. Concrete tanks are stronger, especially when the tank’s base and lid are reinforced with steel. The sides of the tank need some ‘breathing room’ too, usually 45cm to 60cm. These will be re-filled with excavated earth once the tank is in position.

Landmarks and blueprints

Mapping matters because your tank measurements have to include those gaps. Neither the tank itself nor its surrounding spaces should interfere with property boundaries, natural greenery, or municipal infrastructure. So while the yard dimensions themselves may not influence your tank size, you do need a municipal map. This will ensure your tank doesn’t bump into tree roots, power lines, sewer pipes, internet cables, or any other municipal utility line.

You also want to be aware of road reserves and HOA terms – they play a bigger role in tank size than any measurements you can draft.

You want your tanks positioned within easy reach of your downpipes and roof gutters. But you also want it in a relatively open space to allow tank access for cleaning and maintenance. (This can be done using a tank robot.) So even if the tank does sit under the driveway, it has to be placed at an angle the tank robot can navigate.