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Rainwater tanks

Rainwater tanks

Collecting rainwater gives you access to an alternative water source and can help reduce the demand on our drinking water supply network.

Collected rainwater is a great source for outdoor water use such as gardening, irrigation or washing your car.

Rainwater Harvesting 'How To' Brochure (294kb pdf)

What you need to know about collecting rainwater

By using a rainwater tank to collect water, you can save money on your water bill, reduce demand on the city's water supply and have an alternate water supply during water shortages.

Collecting rainwater also means you can:

  • generate your own water supply during an emergency
  • use your collected rainwater to water the garden, wash the car, flush the toilet or do a load of washing
  • make use of a readily available natural resource
  • help protect the environment from the effects of excess stormwater runoff.

Rainwater can be used across a variety of your outdoor and indoor tasks. You can:

  • water the garden
  • wash the car
  • wash the outside of your house
  • top up your spa or swimming pool
  • use it for the laundry
  • flush the toilet.

Did you know that rainwater could be used for approximately 59% of your household water needs?

Average household water use - indoor and outdoor pie chart

When choosing how you would like to use rainwater it is important to be aware of the health and safety and legal requirements.

If the rainwater is to be used for indoor purposes such as flushing toilets, or your rainwater tank is automatically topped up by mains water supply when it gets low, you will need a building consent for the installation of a backflow prevention device. This device is required to be installed by a licensed plumber.

Non-potable water signage

All non-potable water outlets and supply pipes (e.g. a garden hose tap connected to the rainwater tank) must be clearly identified as not suitable for human consumption by displaying a sign that says ‘non-potable water’ or ‘not for drinking’.

You can find out more about signage requirements in the NZ Building Code Clause for Signs.

To register your rainwater tank with Tauranga City Council and request a 'Rainwater tank in use' sign please email waterline@tauranga.govt.nz

Health considerations with rainwater tank use

Urban tank water is not recommended for drinking, cooking or bathing purposes as it may contain contaminants such as bird droppings or bacteria. If you want to drink your rainwater, you will need a building consent to install a treatment device and undertake regular quality testing.

‘If you are using rainwater for your vegetable garden, it’s recommended that you wash all fruit and vegetables thoroughly before eating.’
 
Visit Te Whatu Ora Health New Zealand’s website for more information about health considerations.

Rainwater tanks come in plenty of shapes and sizes to match your needs. The type of rainwater tank suitable for you will depend on what you intend to use the water for, how much water your household needs, where the tank will be situated and how much space is available.

Types of water tanks

Rainwater tanks come in a range of sizes and are constructed from a range of materials, such as plastic or concrete.

If you are already connected to the centralised water network and are short of space, slim-line tanks that act as a fence or small rain barrels that can sit on a deck can be a good option for your property.

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

Common tank types
Type Typical Use Typical Size

Rainwater Barrell

Rain Barrel


Easy to set up, generally small and used for outdoor watering only
Storage ranges from 100 - 1000 litres

Slimline tank

Slimline tank

Good for area with restricted space. Can be tall due to smaller base. Suitable for indoor and outdoor water use Storage ranges from 1000 - 5000 litres

Standard tank

Standard tank

Most commonly round and installed above ground. Suitable for indoor and outdoor water uses Storage ranges from 1000 - 7500 litres

Large tank

Large tank

Used on commercial sites and rural households that are not connected to mains water. Suitable for complete water supply. Storage ranges from 15,000 - 30,000 litres

Underground tank

Underground tank

Good for space-restricted sites including commercial sites. Earthworks will be required to bury the tank. Storage up to 20,000 litres
 
Tank costs

In Aotearoa, rainwater tank costs vary, and it is good to shop around. Costs depend on a variety of things including size, design and the material from which it’s constructed. It’s important to note you may also incur additional costs in the preparation of your site, installation, additional tank parts and fittings, plumbing and electrical services, and consent fees.  

Choosing a tank size

To calculate the size of tank you’ll need to consider:

  • the annual rainfall in your area (the average Tauranga rainfall is approximately 1200mm per annum)
  • your roof’s capture area
  • what you intend to use the water for (is it for indoor or outdoor use, or both?)
  • how much space you have available for the tank.

Rainwater graph

Other factors that might influence the size of your tank include:

  • the size of your property – a large garden will need more water
  • the number of people in your household
  • how reliant you are on the water supply
  • the efficiency of your water-using appliances and plumbing fittings.

You don’t need to have a huge tank to make a difference – even a rain barrel will reduce your outdoor water use, save you money and provide water in an emergency.

Outdoor use

When it comes to outdoor tasks such as watering the garden or washing your car, you can either install a rain barrel or a rainwater tank. During times of low rainfall, smaller tanks may run dry so before installing your rainwater tank, make sure it’s a size that can service your watering habits and possible climatic conditions.

Indoor use

If you are planning to use your rainwater for indoor supply, you will need to install a larger tank.

If rainwater is your sole source of water, you will need at least a 30,000-litre rainwater tank. Talk to your local suppliers to find out what tank size will best suit your local climate and household.

For a basic rainwater tank set up, you will need:
  • A rainwater tank: look for a long-lasting, watertight tank with an opaque exterior, and a tight cover to prevent evaporation and to keep insects, birds and rodents out.
  • Overflow outlet: this makes sure excess water flows back into your existing onsite stormwater discharge point. Please note if you change the stormwater discharge point a consent will be required.
You may also find the following useful but not necessary for all tank installations:
  • Gutter screen and leaf guards: Install these at the top of downpipes to prevent leaves and debris from entering the tank.
  • First flush diverter: The first rainfall usually carries most of the contaminants from your roof (such as dirt, debris and bird droppings). This device diverts the 'dirty' water away.
  • Pump: While gravity-fed systems are an option, most households with a tank on the ground will require a pump to improve water pressure. A pump requires a power supply. Use a registered electrician to safely install your pump if required.
  • Filters: These include simple cartridges, fine mesh and UV filtration systems that can remove sediment, harmful microbes and alter the pH balance of your water. All filters require maintenance and replacement.
  • Chlorination: Consider adding chlorine tablets to improve the quality of your water and prevent algae from forming.

You can collect rainwater from most roof types including pressed metal and clay tiles. Your roof, flashings and gutters must not contain lead or lead paint. These coatings can dissolve and contaminate your water supply.

Gutters and downpipes should be properly sized and sloped to maximise your rainwater collection.

In many cases, you can install a simple rainwater tank on your property without having to apply for a building or resource consent.

Do I need building consent from Council?

A building consent makes sure that all rainwater tank installations meet the requirements of the New Zealand Building Code and that there will be no contamination to the Council water supply network.

A building consent is required if the rainwater tank:

  • is connected to the Council water system as a backup and requires a backflow prevention device
  • if the tank requires internal plumbing for toilet and laundry use
  • is supported by the ground and exceeds 35,000 litres of capacity
  • exceeds 2000 litres in capacity and is supported more than 2 metres above the ground
  • exceeds 500 litres in capacity and is supported more than 4 metres off the ground.

All plumbing must be carried out by a registered plumber and should comply with the New Zealand Building Code. This is covered by your building consent.

If a rainwater tank is classified as a building (does trigger a building consent) then a resource consent may be required.

Building and Resource Consent costs

Tauranga City Council is waiving Building or Resource Consent processing or inspection fees for the retrofitting of a rainwater tank into an existing residential property. This fee change does not appear on the Fees and Charges section of Tauranga City Council website but the Building or Resource Consent processing or inspection fees will be deducted off the final invoice once the consent has been processed. The application must only be for a rainwater tank and not part of a broader consent package does not apply to any notified resource consents. Please note terms and conditions do apply.

If you are unsure about consent requirements visit our do I need a building consent webpage, email buildingduty@tauranga.govt.nz  or phone 07 577 7000 and ask to speak to the building consents team.

Want to discuss further?

Contact our Waterline team on email waterline@tauranga.govt.nz or phone 07 577 7000.

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