Published On: 9th July 2025

Rainwater capture and use – at your place

Did you know you can collect rainwater from the roof of your house to use for everything from filling your pool and watering the garden, flushing the toilet and doing your laundry, right through to showering and drinking*?

Rainwater collection or rainwater harvesting is becoming more and more popular in New Zealand homes as councils prepare to transition to a system where they start charging for water, wastewater and stormwater services.

Harvesting rainwater has a number of benefits including autonomy around your water usage, cost savings, doing your bit towards sustainability and reducing pressure on council systems.

Almost any property can set up a rainwater harvesting system and if you’re thinking of doing so at your place, we’ve compiled some handy information about what’s involved in setting up a rainwater harvesting system at home.

SAVINGS

Keen to save up to 40% on your mains water usage?

SUSTAINABILITY

Wanting to do your bit by collecting and re-using your rainwater?

FREEDOM

Sick of not being able to water your garden or wash your car during restrictions?

Rainbank is available as a kit with a range of dependable Davey pumps to suit a wide range of applications. Talk to your local Davey Master Dealer about the best option for you.

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Rainwater Harvesting FAQs

What is rainwater harvesting and how does it work?

Rainwater harvesting is very simple, basically it takes water collected from your house or garage roof and enables you to then use the water to flush toilets, water the garden or, if you wish, you could choose a system which enables you to drink the collected water.

What equipment do I need for rainwater harvesting?

The equipment needed will depend on what the collected water is going to be used for. Regardless of the end use, you will need to clean and prep your roof, downpipes and gutters before connecting to the tank and equipment. A simple tank and pump set up with the associated pipes and filtration is appropriate for applications which don’t require UV treatment such as garden use, toilets and washing machines. If you want to use the water for drinking, you’ll also need UV treatment to ensure it is free from contaminants. We recommend the Davey Rainbank smart controller to manage your rainwater harvesting system.

How much space do I need for rainwater harvesting?

There are various rainwater harvesting systems available to suit most homes and they can be specified during the planning stages of building a new home or retrofitted into your existing home. You will need space for a water tank (size and location will depend on how much water you want to collect and what it will be used for). In new builds, water tanks are often installed underground, however if you have space, they can be above ground. Your Davey Rainbank controller can be wall mounted, free standing with a cover or installed where the lid is located on the water tank. You will also need to ensure your system has access to water mains, which is usually very simple however you will need your plumber to do the installation as he has the correct qualifications to do so.

Can I switch between rainwater and mains water when needed?

The Davey Rainbank is a pump controller which switches to mains water when the water collection tank is empty and back to tank water when the tank has sufficient water for the float lead to operate the pump (i.e. turn the pump on and off). The Davey Rainbank system requires mains water pressure to operate correctly and is fitted with a backflow prevention valve which stops tank water contaminating the mains water supply.

How much does it cost to set up rainwater harvesting?

The price will vary depending on the size of the tank required to sufficiently supply the dwelling with the water needed for the day to day running of the household and whether the collected water is going to be used for grey water applications such as toilet and laundry or if you will be using it for drinking. (Note – if you want to drink the water then a UV filtration system will be required).

How much money will I save by using rainwater?

It’s not always about the $$! Collecting rainwater means that effectively you are taking storm water out of the council system which means it will not be under extreme pressure during winter months, overflowing into the wastewater treatment facilities.

As for actual dollar savings, there are some families who never see a monthly water bill due to their rainwater providing all their household water. This could be up to $130/ month for an average home which could be a saving of thousands per year.

How do I choose the right size water tank for my house?

This would definitely depend on how the collected water would be used and how much water you require. For an average three bedroom house with one bathroom, a 25,000l to 36,000l tank would be the norm (if space permits). There are various setups ranging from slim tanks installed along side of the house to underground tanks and even tanks that double as fences with hanging gardens.

Do I need a pump to use rainwater in my house?

The pump is the heart of your rainwater harvesting system. You will require either a surface mounted or submersible pump.

How do I know if my roof is suitable for rainwater harvesting?

Most roofs can be used however we suggest caution when installing a system in an industrial area, or in a rural setting which could be within a spray zone. Remember some of our cartridge range can be used for the removal of some pesticides. It’s also important to check your roof doesn’t contain Asbestos before installing a rainwater harvesting system.

Is it safe to drink rainwater?

Yes, it’s safe to drink rainwater so long as the correct precautions are taken before using it. There is only one way to ensure your rainwater is safe for drinking and meets NZ health regulations and that’s by using UV and filtration.

What are the ongoing costs of rainwater harvesting?

To ensure your system keeps delivering it is important to make sure it is in good working condition. This means regular pump maintenance and filter changes. The ongoing costs include:

Pump maintenance and servicing – every 12 months
UV lamp replacement – every 12 – 14 months

Cartridge replacement and quartz sleeve cleaning – every 6 months

Do I need council permission to install rainwater harvesting?

No, you do not need a permit to use rainwater harvesting, although any system that is connected to mains water needs to be installed by a registered plumber.

If I am building a new house, when do I need to decide if I want to include rain water collection/use?

You can either have the system drawn up at the planning stage or after. In most cases it is added after the house has been built.

Are there rainwater harvesting specialists in New Zealand?

All our Davey Master Dealers have been trained in all aspects of rainwater collection and have the recommended stock available. There are a lot of variables when quoting domestic or commercial rainwater harvesting, you should always consult with your local Davey Dealer for the best advice before purchasing your water treatment system.

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How does it work?

The Davey Rainbank is the smart controller part of a rainwater harvesting system which, when integrated with a water tank collecting water from your roof and your existing property plumbing will allow you to seamlessly switch between mains water and your collected rainwater for various household uses.

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How to install a Davey Rainbank

This video is for installers or interested homeowners who want to understand the various installation options and configurations … and how to do them.

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Rainwater capture and use – at your place