Rainwater tanks buying guide

It’s time we stopped wasting precious drinking water on the garden and for toilet-flushing.
Learn more
  • Updated:1 Jul 2008

02.Costs and considerations

Before you start

If you’re interested in installing a rainwater tank, contact your local council, water supplier and health department (if you want to drink the water) first to find out which rules and regulations apply in your local area that could affect your decision.

You may need to submit a development or building application; or there may be restrictions on the tank’s location, colour, height and labelling; or noise regulations for a pump may apply. Your water supplier or a licensed plumber should be able to advise you on plumbing regulations, and your health department on issues about drinking rainwater and preventing mosquitoes breeding.

These initial inquiries should also establish whether you’re entitled to any cash rebates or bill reductions. Rebates can range from $150 to $1500 for the installation of a rainwater tank and depend on the size of the tank and whether it’s connected to a toilet and/or washing machine. Check with your local water or government authority


Tanks can cost as little as a few hundred dollars for a basic, small, freestanding model without pump and extras, to many thousands of dollars for a large, custom-built model with all the bells and whistles. The costs vary depending on the size, material, finish and strength of the tank.

When we checked out prices from a few manufacturers for polyethylene tanks, they ranged from around $700 to $900 for a 2000 L model, from $1000 to $1250 for a 4000–5000 L one and from $1800 to $2000 for a 9000 L tank. It’s worth shopping around.

Further to these costs are any charges for delivery and installation; extra materials (such as pipes, fittings and taps); optional extras (such as a first-flush or backflow-prevention device); a pump (unless you can use gravity for water pressure); and a stand (unless you want to put it on the ground or below it, in which case you may need to factor in costs for special preparation or excavation).

Last of all there are labour costs for a licensed plumber, if you want to connect the tank to your mains water supply, and costs for any additional work that needs to be done to your roof and/or guttering.

And after all these expenses, you’re ready to reap the benefits ... as long as it rains.

Tank facts

Rainwater tanks come in a multitude of sizes, shapes, materials and colours. You can install one next to the house, on top or under it, on a stand, on the ground or below it. Installing a tank below ground is generally more expensive because of excavation costs, but the tank’s out of sight.

  • Cover: All tanks should have a tight-fitting cover so animals and children can’t get access, water won’t be lost through evaporation and light doesn’t enter, which could promote the growth of algae.
  • Size: The tank capacity you need depends on what you want to use it for, the size of your household and garden, your roof area and the annual rainfall in your region. Your water authority may be able to help you work out the size you need, or many sellers of rainwater tanks provide calculators on their websites.
    Sydney Water recommends a minimum tank size of 5000 L in an urban environment, if you want to use the water for toilet-flushing, the washing machine and in the garden (but not for drinking water). Brisbane City Council estimates that a 3000 L tank connected to the hot water system, toilet and for outdoor use can result in 30–40% savings of mains water.
  • Type: Tanks come in many shapes and sizes: typically, they are round, rectangular (modular) or slimline. Round ones come either upright or squat, which may fit well under decking or the like. Slimline tanks are generally a bit smaller, but are popular with people who have limited space for a tank. Tanks can also be installed underground. If you have very limited outdoor space, you could consider an underfloor tank or bladder storage system.
  • Material: Metal tanks are made from corrugated or flat rolled metal and can be galvanised or coated. They often come with a plastic inner lining (Aquaplate) that’ll increase the life of the tank and protect the water quality.
    Polyethylene (poly) tanks are durable and because rust isn’t an issue, tend to be recommended for people living near the ocean. Concrete tanks can be bought ready-made or custom-made on-site. Fibreglass tanks tend to be more expensive: they’re rust and chemical-resistant and designed to withstand extreme temperatures. They’re more suitable for above-ground installation, while all other types can also be installed below ground.
  • Location: To reduce water loss through evaporation from inspection holes, don’t put it where it’ll be in the path of the hot midday sun.

Building a new home?

 Installing a rainwater tank out of the way under the house, at gutter level, or even one that’s completely invisible inside your walls is easier when you’re building a new home (or when doing major renovations) than when retrofitting a system.

This applies even more to a greywater system, which requires, as a minimum, connections to your bathroom and/or laundry plumbing and, depending on its complexity, some space outside.

So it makes sense to consider such environmental features when you’re starting from scratch. In some areas you may even have to incorporate energy and water-efficient features in your building plans to comply with new legislative requirements.

There are companies offering water storage solutions that are built into the house at construction stage. For example, VISION WATER (www.vision-water.com) offers an integrated rainwater harvesting, storage and reticulation system.


Sign up to our free

Receive FREE email updates of our latest tests, consumer news and CHOICE marketing promotions.