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Add an outdoor water tank

Te whakatū kōpapa wai mō waho

Outdoor tanks store water for use in many applications, both domestic and commercial.

You do not need a building consent for a water tank that is to be used for watering the garden or washing a car, or the structure supporting it, if the tank:

  • does not exceed 500 litres capacity and is supported not more than 4m above the supporting ground
  • does not exceed 1000 litres capacity and is supported not more than 3m above the supporting ground
  • does not exceed 2000 litres capacity and is supported not more than 2m above the supporting ground
  • does not exceed 4000 litres capacity and is supported not more than 1m above the supporting ground
  • does not exceed 8000 litres capacity and is supported not more than 0.5m above the supporting ground
  • does not exceed 16,000 litres capacity and is supported not more than 0.25m above the supporting ground
  • does not exceed 35,000 litres capacity and is supported directly by ground.

All building work must comply with the Building Code.

Using water from a tank

If the stored water is to be used for non-potable sanitary plumbing, flushing toilets and laundry (cold water), an authorised person must carry out this work and a building consent is required.

Where sanitary plumbing is supplied with non-potable water, Watercare services must be notified regarding wastewater charges.

All non-potable water outlets and supply pipes, e.g. a garden hose tap, must be clearly identified as such.

If the stored non-potable water is provided with a network supply connection, to top up when required, a suitable backflow prevention device must be included as part of the installation and a building consent is required.

Water filtration

If you use the stored water for flushing toilets and laundry (cold water), you will need filtration devices.

These devices include a gutter guard, leaf slide and first flush diverter.

Maintaining a water tank

The owner/occupier of the premises must ensure the water tank is maintained in a good operating order and the water is in satisfactory condition.

Stormwater drainage

If the storm water drain is altered to accommodate a store water tank, an authorised person must carry out the work and a building consent is required.

This does not include alterations to a down pipe. This is not required as the detention component would be part of a resource consent requirement, to limit peak flow to the network, in conjunction with a building consent.

If your water tank retains stormwater runoff, before slowly releasing it into the public stormwater system, this is considered drainage work and will require a building consent.

Rainwater intended for use as potable water

If rainwater is intended for potable use, several health and safety-related issues are involved, including treating and disinfecting the rainwater to appropriate water standards and avoiding cross connections.

This requires professional advice.

How to check if you need a consent to add a water tank

If you are unsure, call us on 09 301 0101 and speak with the building and planning help desk. 

 By phone

09 301 0101

 In person

​At one of our service centres.

More information

For more information, see the MBIE Building Performance website.

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