Rainwater tanks

You can help to secure our water supply by installing a rainwater tank.

Rainwater tanks help save our drinking water and also help manage stormwater run-off. That’s why Sydney Water is making it easier for you to save water by offering a rebateif you buy and install a rainwater tank.

Choosing the right size tankGenerally, the larger the tank is, the more water can be saved. We recommend a minimum tank size of:• 5,000 litres if you want to use the water for all non-drinking household

use such as flushing toilets, washing clothes, watering gardens and washing cars

• 2,000 litres if you want to use the water for some household use such as toilet flushing and watering a small garden area.

Activity Water Frequency =

Toilet flush(4-star rated dual flush) 12 litres per person a day No. of people =

x 18 litres x 7 days

Toilet flush(11 litre full flush) 55 litres per person a day No. of people =

x 55 litres x 7 days

Washing machine4-star or 5A rated 50 litres a load No. of washes =

x 50 litres x 7 days

OR Washing machine

(other)153 litres a load No. of washes =

x 153 litres x 7 days

Watering your garden 1,000 litres an hourNo. of hours p/week = x 1,000 litres

Estimated weekly rainwater requirement TOTAL LITRES

You should also consider:• how many people live in your home. An average four-person household

uses about 7,000 litres of water each week• the size of the roof catchment area the tank is connected to.

This will limit the amount of water you can collect.

An example of water use over one week might include:• Six loads of washing (4-star / 5A water efficiency rated machine) = 300 litres• Four people using a 4-star water efficiency rated toilet = 336 litres• One hour watering the garden = 1,000 litresUse the table below to estimate how much rainwater you would need based on your weekly water use.

Choosing the tank typePolyethylene tanks are durable, UV-resistant, light and easy to transport. They are available in many sizes and colours and can be placed above or below ground.

Metal tanks are light and easy to transport, can be custom made and are suitable above or below ground. They are usually corrugated or steel coated.

Concrete tanks can be placed above or below ground. They are durable and long lasting. They’re good for preventing algal growth (light can’t penetrate) and they keep water cool.

Fibreglass tanks are lightweight, tolerant of extreme temperatures and are resistant to rust and chemical corrosion. They are easy to transport and come in a large range of colours and sizes. They are best placed above ground.Note: Make sure you speak to your tank supplier about advantages and disadvantages of different tank types before choosing one that’s right for you.

Tanks can be above or below ground, come in a variety of materials and cater to a range of budgets.

How much will it cost?The cost will vary depending on:• the size and type of tank• whether you connect the water indoors• roof, guttering and down pipe adjustments (if necessary)• whether you need a foundation or tank stand for above ground tanks

or excavation work for below ground tanks• the addition of flow restrictors, first flush devices, insect screens,

backflow prevention, gutter guards and other plumbing devices • the need for water pumps (if there is insufficient gravity pressure).

How much space will I need?As a guide, a 5,000 litre round tank will be 1.7 metres wide and 2.3 metres high. To save space you could install your tank below ground or buy a slim-line tank to sit along the side of your house.

Installing a tankPlanning and building requirementsIf the single tank or the total of all tanks on your property is less than 10,000 litres, generally you do not need council approval. If your tank (or tanks) is larger than 10,000 litres, you will need to get permission from your local council and Sydney Water. We recommend that you contact your local council regardless of tank size as they may have specific requirements. Your tank should not be installed within a Sydney Water easement or over a sewer access point. Any overflow from the tank must run to the stormwater system, not the sewerage system.

Plumbing workAlthough most of the information in this section is for plumbers, it is useful to be aware of the work the plumber may need to do.If you are using tank water indoors, you will need to maintain minimum water levels in your tank. A licensed plumber should install a top-up system from Sydney Water mains water supply or a ‘rainwater tank control valve’, that automatically switches to mains water when the tank is empty. Any rainwater tank connected to Sydney Water’s main supply must comply with Sydney Water’s Rainwater Tank Plumbing Guidelines, that require:• the installation of a flow restrictor to ensure the flow rate of water

used to top-up the tank does not affect your or your neighbours’ water pressure

• a visible ‘air gap’ between the pipe from the mains supply and the tank. This ensures rainwater does not flow back and mix with your drinking water

• appropriate backflow prevention (see Backflow prevention devices section) • tank outlets and pipes to be labelled as rainwater.

Backflow prevention devicesBackflow can occur when rainwater from a tank mixes with the drinking water supply. To prevent this, a backflow prevention device needs to be installed at your property boundary.

Above ground tanksIn most cases, Sydney Water will provide a water meter with a backflow prevention device free of charge to customers with an above ground tank and an accessible, standard sized water meter (20 or 25mm meter). Some customers will need to install a backflow prevention device at their own expense. This includes properties where: • the water meter is larger than 25mm• the water meter is inaccessible• the property is unmetered• the water meter is shared between other properties.

Below ground tanksIf you have a below ground tank, you are required to install a testable backflow prevention containment device at the property boundary, or at the master water meter(s) serving the property. If your below ground tank has a connection with Sydney Water’s drinking water supply, you are also required to install an additional backflow prevention device. This may be a physical air gap or a testable backflow prevention device to isolate the tank from the rest of the house.All testable backflow prevention devices need to be tested every year. You will need to pay the installation and annual testing costs. Installing a backflow prevention device can cost from $400 to more than $1,000 depending on your individual plumbing requirements. Your licensed plumber can provide advice about the type of backflow prevention required.If you are unsure about whether you need to install a backflow prevention device, phone Sydney Water on 13 20 92.

PumpsIf your tank is not high enough for gravity to provide the required water pressure, you will need to install a pump (check with your installer about the range of pumps available). Low voltage pumps are generally safer and quieter than high voltage pumps and can be powered by a solar panel and battery system.

First flush devices, screens and guardsFirst flush devices and gutter guards reduce the amount of sediment and other materials entering the tank that pollute the water. Use insect screens to cover all tank openings. This prevents mosquitoes entering and breeding in the tank.

Maintenance requirementsNSW Health recommends that rainwater tanks are well maintained. In general you need to:• regularly clean leaves, debris and overhanging tree branches from

your roof, gutters, first flush devices and insect screens• check for mosquitoes. If you have them, try to find out how they entered

the tank and block their access• check the bottom and sides of your tank for sludge every two to three

years. Siphon the sludge out or empty the tank. Sediment in the tank may block your irrigation system or discolour your toilet cisterns and washing machine. Check the Yellow Pages for professional tank cleaners.

For more information visit www.health.nsw.gov.au

Need more information?For information on:• rainwater tanks and plumbing standards, visit www.sydneywater.com.au • tank suppliers, look under ‘Tanks and Tank Equipment’ in the Yellow Pages• plumbing requirements talk to your licensed plumber and/or refer to the

NSW Code of Practice for Plumbing and Drainage available at www.environment.nsw.gov.au

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Contact usVisit www.sydneywater.com.au EnquiriesCall 13 20 92Service difficulties and emergenciesCall 13 20 90Postal addressSydney Water PO Box 53SYDNEY SOUTH NSW 1235