Rainwater tanks are becoming an increasingly practical choice for homes, lifestyle properties and businesses across New Zealand. Whether you want to reduce your reliance on mains water, collect rainwater for your garden, or create a more reliable household water supply, choosing the right rainwater tank can make a significant difference.

For Auckland and other parts of New Zealand, there are many options available, including slimline water tanks, standard round tanks, large rural tanks and underground rainwater tanks.

This guide explains what you need to know before buying and installing a rainwater tank in NZ.

What Is a Rainwater Tank?

A rainwater tanks is a storage tank designed to collect and store rainwater from a building’s roof. Rainwater flows through gutters and downpipes before being directed into the tank.

The stored water can be used for different purposes depending on how the system is designed. Common uses include:

Garden and lawn watering

Washing cars

Toilet flushing

Laundry

Outdoor taps

Irrigation

Household water supply

Emergency water storage

Auckland Council notes that rainwater tanks are available in different sizes and types, depending on available space and how the stored water will be used.

Why Install a Rainwater Tank in NZ?

New Zealand receives regular rainfall, making rainwater harvesting a useful way to make better use of water that would otherwise run into the stormwater system.

1. Reduce Mains Water Use

A rainwater tank can provide an additional water source for outdoor and selected household uses. This can help reduce demand on the mains water supply.

2. Water Your Garden

Rainwater is particularly useful for gardens, lawns and landscaping. Instead of relying entirely on mains water, you can use stored rainwater when your garden needs it.

3. Improve Water Resilience

Having stored water available can provide an additional level of resilience for your property, particularly during periods of water restrictions or supply issues.

4. Support Better Stormwater Management

Rainwater tanks can capture roof runoff and temporarily store it rather than allowing all of the rainfall to enter the stormwater system immediately. Auckland Council identifies stormwater management as one of the benefits associated with rainwater collection.

Types of Rainwater Tanks Available in New Zealand

Choosing the right tank depends on your property, available space, budget and intended water use.

Slimline Water Tanks

Slimline tanks are designed for properties where space is limited. Their narrow profile makes them suitable for many urban homes and smaller sections.

They can be a good option when you want water storage without taking up too much ground space.

Standard Water Tanks

Standard round tanks are one of the most common options for residential properties. They are available in a wide range of capacities and can be used for outdoor or indoor water applications.

Large Water Tanks

Large water tanks are commonly used on rural properties, lifestyle blocks and properties that depend heavily on stored rainwater.

If your property is not connected to a reliable mains water supply, a larger tank may provide greater storage capacity.

Underground Rainwater Tanks

Underground tanks can be useful where above-ground space is limited or where the tank needs to remain visually discreet.

However, underground installation generally requires additional excavation and site preparation.

Auckland Council’s guidance identifies rain barrels, slimline tanks, standard tanks, large tanks and underground tanks as common rainwater tank types.

What Size Rainwater Tank Do You Need?

There is no single tank size that is right for every New Zealand property.

The ideal rainwater tank size depends on factors such as:

Roof catchment area

Local rainfall

Number of people living at the property

Household water consumption

Whether the tank is for garden use or household use

Available installation space

Whether mains water is available

How much water you want to store

For example, a small tank may be suitable for garden watering, while a larger tank may be more appropriate for a rural property relying heavily on rainwater.

If you are unsure, it is worth speaking with a local water tank supplier or installer before choosing a capacity.

Rainwater Tanks NZ: What Homeowners Should Know

For homeowners looking for rainwater tanks in NZ, available space and local requirements are important considerations.

Auckland has many properties with limited outdoor space, particularly in urban and higher-density areas. This makes slimline and compact water tanks an attractive option for some homeowners.

Auckland Council has also made changes intended to make residential rainwater tank installation easier in many situations. However, requirements can depend on the type of tank, its location and how the system connects to the property.

If the tank is connected to internal household plumbing, additional requirements may apply. Auckland Council states that building consent requirements can apply to rainwater reuse systems, while some outdoor-only systems may fall under exemptions.

Always check the current requirements for your property before installation.

Rainwater Harvesting for Homes

A typical residential rainwater harvesting system works by collecting water from the roof and directing it through gutters and downpipes into a storage tank.

A basic system may include:

Roof → Gutters → Downpipes → Filter → Rainwater Tank → Pump → End Use

Depending on the application, the system may also include filtration, pumps, backflow prevention and tank-to-mains changeover equipment.

Rainwater can be used for non-potable purposes such as toilets, laundry and outdoor taps when the system is appropriately designed and installed.

Rainwater Tank Installation

Professional rainwater tank installation can help ensure the tank, plumbing, pump and connections are suitable for the property.

Before installing a tank, consider:

Location

Choose a location with enough space for the tank and access for installation and future maintenance.

Base

The tank needs an appropriate, stable base capable of supporting its weight when full.

Gutters and Downpipes

Your roof catchment system needs to direct water efficiently into the tank.

Overflow

A properly designed overflow system is essential so excess water can be safely managed during heavy rainfall.

Pump

If stored water needs to be supplied under pressure, a suitable pump may be required.

Plumbing

If rainwater is being connected to household plumbing, the installation needs to meet applicable New Zealand requirements.

How to Maintain a Rainwater Tank

Buying a quality tank is only part of the process. Regular maintenance can help keep your rainwater harvesting system working effectively.

Useful maintenance tasks include:

Clean gutters regularly

Check inlet filters

Inspect the tank for damage

Check pumps and pipework

Monitor the water level

Keep the tank area clear

Arrange professional tank cleaning when required.

Check overflow and drainage arrangements

If you depend on tank water for your household supply, regular monitoring is particularly important. Auckland Council recommends checking water levels, monitoring usage and keeping gutters clear for properties relying on rainwater.

Rainwater Tank vs Water Tank: What’s the Difference?

The terms rainwater tank and water tank are often used interchangeably, but they can refer to slightly different applications.

A rainwater tank specifically collects and stores rainwater, usually from a roof catchment.

“Water tank” is a broader term that can include tanks used for rainwater, potable water, rural water storage, industrial applications and other purposes.

When searching for a tank in New Zealand, you may see terms such as:

Rainwater tanks NZ

Water tanks NZ

Rainwater tanks Auckland

Water tanks Auckland

Residential water tanks

Rural water tanks

Slimline water tanks

Underground water tanks

Rainwater harvesting tanks

How Much Does a Rainwater Tank Cost in NZ?

The cost of a rainwater tank installation depends on more than the tank itself.

Factors that can affect the overall price include:

• Tank size
• Tank material
• Tank shape
• Delivery
• Site access
• Base preparation
• Plumbing
• Pumps
• Filters
• Excavation
• Electrical work
• Installation labour
• Household plumbing connections

For this reason, it is better to compare complete installation quotes rather than looking only at the advertised tank price.

Choosing the Right Water Tank Supplier

When comparing water tank suppliers in NZ, look beyond price.

Consider:

• Tank quality
• Warranty
• Available sizes
• Material and construction
• Delivery options
• Installation services
• Pump and filtration options
• After-sales support
• Experience with local properties
• Compliance with relevant New Zealand requirements

Auckland has a number of local suppliers and specialists offering rainwater tanks and related services, so homeowners should compare the specifications and installation requirements rather than choosing purely on price.

Final Thoughts

A well-designed rainwater tank system can be a valuable addition to a New Zealand home, rural property or business. From compact slimline tanks for Auckland properties to larger water tanks for rural homes, there are options to suit different water-storage needs.

The key is to choose the right tank size, installation location and system components for your property.

If you’re comparing rainwater tanks in Auckland or across New Zealand, get advice from an experienced local supplier and consider the complete installation requirements—not just the tank itself.

Frequently Asked Questions About Rainwater Tanks

Are rainwater tanks worth it in New Zealand?

For many properties, rainwater tanks can be a practical way to collect and store rainfall for garden watering, outdoor use and selected household applications. Whether a tank is worthwhile depends on your water usage, property and installation cost.

What is the best rainwater tank for a small Auckland section?

A slimline rainwater tank can be a suitable option where ground space is limited. The best size and shape will depend on the available installation area and how much water you want to store.

Can rainwater be used inside the house?

Yes, rainwater can be used for applications such as toilet flushing and laundry when the system is properly designed, installed and connected. Additional plumbing and compliance requirements may apply.