Rainwater is a free and renewable resource that often goes to waste. In New Zealand, rainfall varies widely – from the wet West Coast to the drier eastern regions – but almost every household can benefit from collecting and using rainwater. By harvesting rainwater, you can save money, reduce pressure on local water supplies, and make your home more sustainable. Here’s how to get started.

Why Harvest Rainwater?

Drinking water is treated to a high standard, making it safe for consumption – but we use it for many tasks that don’t require that level of purity, such as watering the garden, washing the car, or flushing the toilet. By using rainwater for these purposes, you can cut your use of treated water by up to 30–40 percent.

Rainwater harvesting also helps reduce stormwater runoff, which can cause flooding and carry pollutants into rivers and the sea. By storing rainwater on your property, you help ease the load on stormwater systems and protect local waterways.

How a Rainwater System Works

A rainwater harvesting system collects water from your roof through gutters and downpipes. The water passes through a filter that removes leaves and debris before entering a storage tank. From there, it can be used directly for outdoor tasks or pumped into the house for non-drinking uses.

There are two main types of systems:

• Simple collection for outdoor use – a rain barrel or tank connected to a downpipe, where you can draw water manually for garden use.
• Plumbed-in systems – a more advanced setup that supplies rainwater to toilets, washing machines, or outdoor taps through a pump and filtration system.

If you plan to use rainwater inside your home, you’ll need a qualified plumber to install the system and ensure it’s kept separate from the mains water supply, as required by New Zealand building regulations.

What Can You Use Rainwater For?

Rainwater is not suitable for drinking unless it’s properly treated, but it’s ideal for many everyday tasks:

• Garden watering – plants often prefer rainwater because it’s soft and free of chlorine.
• Car washing – rainwater leaves fewer spots and streaks than tap water.
• Toilet flushing – one of the biggest water uses in most homes.
• Laundry – with the right system, rainwater can be used in washing machines, helping reduce detergent use and limescale buildup.

Avoid using untreated rainwater for cooking, drinking, or personal hygiene.

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Getting Started

1. Check your roof and gutters – Roof materials like steel, tile, or concrete are suitable for collecting rainwater. Avoid roofs with lead flashing or treated timber.
2. Choose the right tank – For garden use, a 200–500 litre barrel may be enough. For household systems, tanks typically range from 2,000 to 10,000 litres, depending on rainfall and usage.
3. Install filters and an overflow – A filter keeps debris out of the tank, and an overflow pipe directs excess water away safely during heavy rain.
4. Decide on placement – Above-ground tanks are cheaper and easier to install, while underground tanks save space and keep water cooler.
5. Maintain your system – Clean filters regularly, check gutters for blockages, and flush the tank annually to remove sediment.

Cost and Environmental Benefits

A basic rain barrel can cost under a few hundred dollars, while a fully plumbed system may range from $3,000 to $10,000 including installation. Over time, you’ll save on water bills and reduce your household’s demand on municipal water supplies.

The environmental benefits are just as important. In many parts of New Zealand, especially during dry summers or drought conditions, water restrictions are common. By using rainwater, you help conserve treated water for essential uses and reduce the strain on local reservoirs and aquifers.

Make It Part of Your Sustainable Lifestyle

Rainwater harvesting is a simple, practical way to live more sustainably. It requires some planning and maintenance, but the rewards are both financial and environmental. Start small with a rain barrel, and expand your system as you see the benefits.

Once you experience how easy it is to use nature’s own water, it quickly becomes a natural part of everyday life – and a meaningful step toward a more resource-conscious home.