Are water tanks the most efficient way to save water in Darwin?

It might seem logical to use rainwater from a tank to water your garden, but in our varying climates, that doesn’t work very efficiently.

When it rains and tanks fill easily, gardens rarely need extra water. Then in the dry season and hot summer months, when we need water most, tanks quickly run dry.

Let’s put it in perspective:

Most urban homes can fit a small to medium tank - about 2–3 metres in diameter, holding 5,000 to 10,000 litres. For context, the average Darwin household uses about 370,000 litres of water per year, with 57% of that used outdoors. That’s around 210,000 litres of water used in the garden per year.

With no rainfall for roughly six to seven months, tanks would sit empty for much of the dry season. During the wet, they’d overflow, causing runoff and maintenance issues at a time when watering is barely needed.

Water use in the home

You can plumb a rainwater tank into your home to supply areas like toilets and washing machines, but the impact is limited. These areas make up a much smaller share of total household consumption:

Toilets: less than 5%

Kitchens and laundries combined: around 7%

So, while tank water can replace a little potable water, it won’t make nearly as much difference as cutting back on garden watering.

The bottom line

Reducing garden water use by shortening watering times and adjusting irrigation schedules is a far more effective way to save water than installing a rainwater tank.

The cost of buying, installing and maintaining a tank, combined with the challenge of keeping it full during the long dry season up in the Top End and hot summer months in Central Australia, makes it a less practical option for most homes.

That said, any effort to save water is a good one, and tanks can still play a useful role if used wisely.

Smart ways to use a rainwater tank

Pool top-ups: About 2% of household water goes into pools. Use your tank water for topping up during the hotter months. It won’t run out too quickly.

Small, efficient garden beds: Use tank water on a rock garden or native plants that only need about 10mm once or twice a week.

Large blocks: If you have space, install multiple large tanks and set up a slow-drip irrigation system to stretch your stored water.

Drinking water: You can use tank water for drinking by filling jugs for the fridge or plumbing it to a separate kitchen tap. Make sure to maintain the tank properly to meet national water quality standards.

Maintenance checklist:

✅ Every 3 months: Clean gutters to prevent animal droppings from entering the tank.

✅ Every 3 months: Check the mosquito mesh for damage to keep insects and vermin out.

✅ Every 6 months: Inspect water quality - look at colour, smell, and sediment levels.

✅ Every 6 months: Check pumps and pipes are intact and working.

✅ Every 2 years: Desludge the tank. It’s recommended you hire a qualified contractor.