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Choosing a rainwater tank

The type of rainwater tank suitable for you will depend on what you use the water for, how much water your household needs, where the tank could go and how much space is available.

Types of water tanks

Rainwater tanks come in different shapes and sizes.

They can also be made from varying materials, including plastic or concrete.

If you are already connected to the centralised water network and are short of space, slim-line tanks are a good option. They can fit along the side of your house, fence, garage or other structure.

Bladder tanks are designed to fit under floors and decks, making use of previously unused space.

For more information, see Rainwater tank suppliers.

Retention tanks

Retention tanks retain water for future use.

​Water type ​Water use ​Tank type
​Non-potable (non-drinking water)
​Outdoor use, such as washing a car or watering garden ​Non-potable (single use) retention tank or rain barrel


​Outdoor use, toilet flushing and laundry use

​Non-potable (single use) retention tank

​Potable water (full drinking water supply)

​Outdoor and indoor uses, including kitchen and bathroom water supply

Water must be purified

Most suitable for households NOT connected to centralised water network

​Potable (or complete supply) water retention tank

Stormwater detention tanks

Detention tanks capture rainwater and store it, slowly releasing it back to the stormwater network.

This contributes to reducing the flow of stormwater runoff and minimises the negative effects on the environment, such as bank erosion, sewer and stormwater overflows.

A detention function can be added to a retention tank to make it a dual-purpose system.

See the Auckland Design Manual website for more information on stormwater management devices.

Guide to choosing a rainwater tank

Read our practical guide for information on types of systems, choosing a size, components and what consents you need.

Choosing a tank size

Use our rainwater tank size calculator to work out what size tank your household would need.

The right tank size depends on several factors:

  • What the water will be used for (outdoor, laundry, toilet etc).
  • How much water you can collect from your roof.
  • How much space there is for the tank (underground or above ground).
  • The number of household occupants the tank will cater for.
  • What your property zone is.
  • How reliant you are on water supply.

Generally, the larger the tank, the more effective it will be at capturing a greater volume of roof rainwater runoff and storing it for later use. However, even smaller tanks can provide some household benefits.

There are many tank sizes to choose from, ranging from 200-litre rain barrels (a simple barrel with a tap) to 25,000 litre tanks that connect to internal plumbing for full water supply.

A registered plumber or water tank supplier can offer advice on the best tank to choose and where it should go on your property.

You can email hwrainwatertank@aucklandcouncil.govt.nz if you have questions on rainwater tanks.

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