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Flooding and storm events
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1. What you need to know before applying for a rainwater tank consent

Before checking whether you need a consent for your rainwater tank, there are a few things you need to think about.

Consider how you will use water from the rainwater tank

  • Outdoor use — if rainwater is to be used for outdoor use only (such as watering the garden and car washing) and the rainwater tank is not connected to your internal plumbing, you may not need a building consent.
  • Indoor use (non-potable) — if the rainwater is to be used for indoor non-potable (non-drinking) purposes (for example, flushing toilets and cold-water laundry), you will need a building consent and a licensed registered plumber to carry out this work.
  • Drinking water — if the rainwater tank is to be used for full water supply, including drinking, dishwashing, cleaning teeth and showering, you will need a building consent and a licensed registered plumber to carry out this work.
  • Commercial / business use — if the rainwater tank is to be used for commercial or business reasons (e.g. commercial carwash, concrete mixing or other general business uses) you will need to engage a design professional for your specific situation - see Free Advice before submitting a consent application.

Consider what tank size you need

To determine the best size rainwater tank to meet your needs, think about:

  • the purpose of your tank (e.g. indoor or outdoor use)
  • your roof size
  • the number of people in your house
  • your dependency on tank water (e.g. whether you are connected to the mains water supply network or not).

Use our rainwater tank size calculator but also discuss your specific requirements with tank suppliers and/or an engineer.

Where to place your tank

  • Consider placing your rainwater tank near an existing downpipe, ideally down the side of your property or at the back away from street view.
  • Make sure the placement of your rainwater tank does not block any windows and maintains outdoor living space.
  • Wherever your rainwater tank is positioned, the overflow needs to drain to an existing onsite drainage point. This is where the rainwater from your guttering and downpipe would have gone before installing the tank.
  • Tanks can also be positioned below ground, under decking and above ground.

When you may need a building consent

Positioning your rainwater tank on a supporting structure

You may need a building consent if your tank will be on top of a supporting structure instead of on the ground. The building consent process checks for health and safety requirements under the NZ Building Code, including structural stability.

Whether your proposed tank on a supporting structure needs a building consent depends on the volume of the tank in relation to the height of the structure.

You may not need a building consent for a tank on a supported structure if it meets Exemptions Guidance for Schedule 1 of the Building Act 2004 (PDF 8.9MB) criteria.

Altering a stormwater drain to fit a rainwater tank

If the stormwater drain will be altered to fit a rainwater tank, a licensed registered drainlayer must carry out the work and you will need a building consent, unless the drain alteration is minor.

If you have a detention tank that holds stormwater run-off before slowly releasing it into the public stormwater system or a dual-purpose detention and retention tank, you will need a building consent.