Rainwater tanks

Installing a rainwater tank can save large amounts of water for your home or garden.

Water tank Benefits include:

  • saving money on water bills
  • less reliance on town water supplies 
  • catching rainwater so less goes down the drains

A rainwater tank is an investment so make sure you do some research and planning before buying one. 

Having a rainwater tank is not a ‘free pass’ for water use. 

See residential water restrictions 

What can I use rainwater for?

Before you buy and install a rainwater tank it's important to think about how you're going to use the water.

As an extra source of water

One of the best ways to save our precious drinking water is to avoid using it for purposes like watering the garden. (All mains water is treated to drinking water standards, but less than 5% of this water is used for drinking.)

Watering your garden is the easiest use of tank water, as you generally only need the supplier to install the tank, rather than a licensed plumber.

You can save money by sending tank water to your toilet, washing machine or hot water system, but you'll need a licensed plumber to connect them to your tank.

If you're using tank water to flush toilets then a top-up system from the mains water supply is also required.

Uses for non-potable tank water (not for drinking): 

  • toilet flushing
  • washing clothes (cold water only) 
  • car washing
  • filling swimming pools or spas
  • ornamental ponds

As the only source of water (for drinking water and indoor use)

Rainwater tanks are not generally recommended for drinking in urban areas due to traffic and industry emissions that can settle on roofs. 

In urban areas NSW Health recommends the public water supply for drinking and cooking. Tweed's town water supply remains the most reliable source of safe, quality drinking water. 

Tank water used for household drinking, food preparation or bathing should meet water quality guidelines to protect you and your family’s health. 

If in doubt, you may want to have your water tested. See Tweed Laboratory Centre

Your tank will need to be cleaned regularly, usually once every two years.

How do I choose a rainwater tank?

Make sure you know:

  • how much water you use
  • how rainwater can be used
  • different purposes and manufacturing materials for tanks
  • expected rainfall
  • the size of tank that suits your needs
  • where to locate your tank

You will need a licensed plumber if you’re connecting your tank to town supply or to fittings and fixtures inside your home.

What size tank do I need?

Council’s policy recommends a minimum size of 5000L for a rainwater tank. As a guide, a tank should hold a minimum of 4 weeks supply of water. If you use 2000L of tank water each week then you should aim for a 8000L tank. 

The size of your tank will depend on a number of factors including:

  • Roof area: the amount of water that can be collected depends on the size of your roof. The tank should be connected to the largest area of your roof via the stormwater down pipe. Each square metre of roof area collects 1 L of water for every 1 mm of rainfall.
  • Rainfall: average annual rainfall where you live
  • Demand: this depends on the number of people in your household and how water is used

If your tank is going to be used as a secondary supply (e.g. to the town water supply), tank size is not such a critical issue.

Where should I put my tank?

Tanks take up a lot of space, but there are now lots of options beyond the standard round tank.

Ideally your tank should be located in shade. This helps to keep water temperature low, and reduces evaporation and possible bacterial growth.

Above ground

Round tanks and space efficient tanks are generally the most cost effective options.


Installing a rainwater tank underground can save space in your yard but can cost twice as much as above ground options.

They need to be made from stronger materials and structures and often require weighting or concrete reinforcement. 

Underground tanks are lower than the ground level so you will need a pump. NSW regulations require additional backflow prevention due to the risk of groundwater contamination.

Under the house or deck

A great space saving option for a house on stumps or stilts is to put a tank under the house or beneath decking. Rainwater bladders are ideal because they are durable and easy to install.

Against a wall

Another space saving option is tanks that go against walls or act as garden walls. Some models can be joined together to make up larger water storages.

State and Environmental Planning Policies (exempt and complying Development Codes) 2008:

What material should my tank be made of?


Plastic tanks respond well to bumps, are lightweight and non-corrosive (rust isn’t an issue). These are often the cheapest tanks. Space saving flexible water bladders can fit into spaces that hard tanks cannot, allowing the best use of space.

Sheet steel (Colorbond steel or galvanised) or stainless steel

These tanks come with corrosive resistant coatings to prevent rust. There should be at least 2 metres of plastic pipe between a steel tank and copper, brass or bronze fittings as they can cause corrosion.


Often more expensive, fibreglass tanks are durable and resist corrosion. A tank which is manufactured with sufficient pigment to prevent light entering the tank is recommended to prevent algae.


These tanks are strong and heavy which means they can be installed underground. New concrete tanks may need to be flushed clean because they can release excess lime leading to a high pH in the water. Some concrete tanks require a lining to be installed.

Construction material, size and installation guide

Before installing your rainwater tank

Seek professional advice on:

  • approvals
  • plumbing
  • preparation (such as foundations and guttering)
  • tank maintenance
  • accessories such as pumps, backflow prevention valves and fittings

Also consider costs for delivery and installation.

When should I install my rainwater tank?

The best time to install a rainwater tank is when you don’t need it.

Fitting your tank at the beginning of the wet season means you will have as much water as possible during the dry season.

What plumbing is needed?

A plumber will give you advice about: 

  • water tanks
  • pumps
  • filters
  • first flush diverters
  • connections, pipes and fittings
  • mosquito proofing
  • backflow prevention valves
  • gutters
  • foundations
  • cost

A licensed plumber is required by law when a tank is connected to the mains water supply.

A plumber is also required to connect your gutters to your tank and to install a stormwater overflow. 

Some tank installations (large tanks) may need a building permit (also needed if the tank is connected inside the house).

How to look after your rainwater system

Protect your water quality: 

  • regularly inspect and clean your gutters and screens of leaves and debris 
  • use gutter guards and a first-flush filter to keep debris out of your rainwater system 
  • tanks should be checked for sludge at least every 2-3 years
  • tanks should be cleaned at least every 5 years to remove sediment on the bottom
  • a well looked after tank will prevent mosquitoes from breeding 

Your tank supplier or a licensed plumber can give you advice on looking after your tank. 

Trickle top-up systems 

Some rainwater tanks include a float valve inside the tank. When the water level gets too low, the float valve triggers a trickle top-up from mains water. 

Trickle top up systems are not recommended for new tank installations.

All new development must have a BASIX certificate which means most have a tank and a mains water top-up system. Top-up systems are mandatory if toilets are flushed.

Mains water trickle top-up systems must be turned off during water restrictions.

Are there rebates for installing a rainwater tank?

Council does not offer any rebates for rainwater tanks.

Do I need approval to install a rainwater tank?

Depending on the size and use, you may need Council approval to install a rainwater tank.

See the rainwater tank installation checklist(PDF, 21KB) or contact us to find out.

If you’re installing a rainwater tank on a residential property in an urban area, and you're connected to the town water supply — you need to read Rainwater tanks in areas with reticulated water(PDF, 3MB).