Green Muze

Rain falls on your roof every year, and most of it runs straight to the drain. A rainwater tank lets you catch some of it and use it around the home. It can water the garden, flush toilets and cut how much mains water you buy.

A tank is a long term purchase, so it pays to plan it properly. Size, plumbing, roof materials and upkeep all affect how well it works. Rules also vary between states and councils, so check local requirements before you buy.

What rainwater can be used for

The NSW Government water factsheet says rainwater can be used without treatment for several jobs. These include watering gardens, washing cars and flushing toilets. NSW Health adds laundry to the list of uses outside drinking. These are the uses where a tank gives the best return in a town or city.

Drinking is a different matter. In urban areas, NSW Health recommends using public water for drinking and cooking. Rainwater tanks are widely used for drinking in rural Australia where there is no town supply. If you live in town, it makes sense to plan your tank for the garden, toilet and laundry.

Why a tank helps beyond your water bill

A tank reduces how much water a home draws from the town supply. It also reduces the stormwater running off your block into drains and waterways. The NSW factsheet notes this can help reduce local flooding and soil erosion. Across a whole suburb, those small savings add up.

How we handle water at the street and suburb level matters too. Our article on the environmental costs of poor town planning looks at the bigger picture in Western Australia. Household tanks are one small part of a better approach. They work best alongside good planning, permeable gardens and careful water use.

Choosing a tank type and size

The South Australian Government describes two broad tank types. Traditional stand alone tanks can be installed almost anywhere on your property. Modular tanks are slimmer and sit against the house to save space. Your local council can advise on selection and suppliers.

Supply is limited by tank size and by rainfall, and rainfall is not predictable. The NSW factsheet says tanks are best suited to higher rainfall areas. Think about the size of the roof area that will drain to the tank. Then think about which jobs you want the water for, since toilets use water all year while gardens need it most in summer.

New homes and state rules

Some states set minimum requirements for new homes. In South Australia, rainwater tank rules require an extra water supply for new homes and some extensions. Most people meet this with a plumbed tank of at least one kilolitre. It must connect to a toilet, a water heater or all cold water laundry outlets.

In South Australia that extra supply must be in place before the home or extension is occupied. Building consent applications must show the tank size, location, catchment area and plumbing details. Other states have their own building and planning rules. Check with your council or state building authority before you order.

Roof materials and water quality

Rainwater quality depends on what it touches on the way to the tank. The NSW factsheet notes that roof and connection materials matter. Leaves, dust and droppings on the roof also end up in the water. In cities, airborne pollution from traffic and heavy industry can affect quality as well.

The NSW Health guide to rainwater tanks lists materials to avoid in the catchment. Avoid lead flashing and pesticide treated timber. Do not collect from roofs painted with lead based paint or coated with bitumen based material. Some PVC pipes may contain lead, so use pipe and fittings rated for drinking water.

New roofs need care too. NSW Health suggests discarding the first few runoffs from a new concrete tile or metal roof. The same applies to roofs coated with acrylic paint. After that settling period the roof can feed the tank as normal.

Plumbing, screens and pumps

Every tank in South Australia needs an overflow device and a mosquito proof screen that will not break down. NSW Health also advises mesh covers and strainers on the inlet and overflow. Keep access covers sealed tight while still allowing access for cleaning. In South Australia a licensed plumber must install the piping and complete a certificate of compliance.

Most tanks need a pump to deliver water at the same pressure as mains supply, according to Sydney Water. External pumps sit on the ground and tend to last longer. Submersible pumps sit inside the tank, are quieter and take up no extra space. Their intake should be raised off the floor so they do not draw in settled dirt.

Sydney Water suggests a small external pump for simple home use. Smaller pumps are more energy efficient, and the right size depends on your block and how you use the water. A pump cover can reduce noise and protect the pump from weather. It is worth placing the pump away from bedroom windows.

Keeping the tank clean

NSW Health describes rainwater collection as low maintenance, not no maintenance. Inspect the roof and gutters every three or four months and clear leaves and debris. Trim overhanging branches where you can. Do this before seasons when heavy rain is expected.

Check the tank for sludge at least every two to three years. Sludge can be removed by siphoning or by emptying the tank fully. A first flush device diverts the dirtiest water after a dry spell so it never reaches the tank. Clean all screens regularly so they keep insects and leaves out.

The owner pays for the upkeep of the roof, gutters, tank and pump. The NSW factsheet points out that a neglected or disconnected tank puts more demand on the town supply. A simple calendar reminder for gutter checks makes the job easy. It keeps the system doing what you paid for.

Using tank water in the garden

The garden is where most homes notice the benefit first. Tank water lets you keep plants alive through dry spells without leaning on mains water. Pair it with mulch and low water plants for the best result. If you are also trying to cut chemicals outside, our guide to natural weed control keeps runoff cleaner.

Think about outdoor surfaces as well. Hard paving sends water straight to drains, while gardens and permeable surfaces let it soak in. If you are planning a deck near the tank, our article on sustainable decking covers material choices. Planning the tank, deck and garden together saves rework later.

Counting the cost

A tank system can be expensive to install. The NSW factsheet says the cost is usually recovered over 10 to 15 years, and rebates may be available. Check with your water utility and state government for any current offers. Ask your plumber for a quote that covers the tank, pump and connections together.

If you are already planning building work, our guide to sustainable home renovations covers other ways to cut water and energy use. A plumber can often run tank connections while walls and floors are open. That makes it simpler to connect toilets and laundry taps. It also avoids the cost of opening up finished rooms later.

Frequently asked questions Can I drink water from my rainwater tank?

In urban areas NSW Health recommends public water for drinking and cooking. Rainwater is suitable for toilets, laundry and gardens. In rural areas without town water, tanks are widely used for drinking when properly maintained.

Do I need approval to install a tank?

It depends on your state and council. In South Australia a licensed plumber must install the piping and provide a certificate of compliance. Check with your local council before you buy.

How often should I clean my tank?

NSW Health suggests checking the roof and gutters every three or four months. Check the tank for sludge at least every two to three years. Clean the screens regularly as well.

Do I need a pump?

Most tanks need a pump to supply water at the same pressure as mains water. A small external pump suits simple home use. Smaller pumps are also more energy efficient.

This article is general information only. Rules for rainwater tanks, plumbing and building approvals differ by state and council and can change. Speak with your local council and a licensed plumber before installing a tank.