Rainwater tanks - new builds and retrofitted tanks

Appropriate roof materials include:

• Terracotta tiles
• COLORBOND® steel
• galvanised iron
• ZINCALUME® steel
• fibrocement
• polycarbonate or fibreglass sheeting
• slate.

If you’re only using water from your tank outside your house, you do not need approval. However, if you want an internal connection, you need plumbing approval.

If your tank is internally connected^* to your toilet and washing machine:

• a 10,000L (2200gal) rainwater tank can supply between 20% and 30% of your average daily water needs
• a 22,000L (5000gal) rainwater tank can supply between 30% to 40% of your average daily water needs.

^*In line with Toowoomba rainfall records.

Find a suitable location for your tank

When choosing a location for your tank, think of areas in your house and garden where water is most needed. Look at the location of existing downpipes and decide if they’re right for your tank. Before placing the tank, make sure it can service the important areas of your home. You also need access to service the tank as well.

Check your tank’s placement to make sure it won’t block your neighbours’ natural light and ventilation or be too noisy for you or your neighbours.

If your rainwater tank doesn't fit where you want it placed, check for different tank shapes and sizes. Consider a different tank location. This could be above ground or below your ground surface tank.

To reduce noise, make sure your pump is designed with a minimum sound power rating. You must keep it housed to reduce the noise.

We recommend using a submersible bore pump pressure system. These systems:

• are very quiet
• can be used for tanks
• may eliminate the need for pump housing.

Check the best roof section for catching water

By increasing your tank’s catchment, you can improve your tank’s ability to supply water when you need it most. Considering a roof catchment area that can service the tank is important. Many installations use only about half a roof’s total area.

1L of water = 1m² of roof area x 1mm. If you receive 10mm of rainfall, every 1m² of roof area draining to the tank will collect 10L.

There are many different materials available at a range of prices. Check that your tank meets Australian standards.

Since 1 September 2014, rainwater tanks and water saving measures on new dwellings and commercial buildings have been mandatory.

Understanding the Queensland Development Code for rainwater tanks on new builds

Queensland Development Code (QDC) mandatory part (MP) 4.2 applies to any new class 1 (a)(i)buildings (single detached dwellings) on blocks greater than 250m².

Dwellings on blocks less than 250m² are exempt. QDC 4.3 is applicable for any new commercial buildings (class 5 to 9).

Units are exempt.

As the definition of units is unclear in the Building Code of Australia (BCA), we consider the definition to be as defined in BCA Volume One Part 3 A3.2 Classifications Class 1a (ii) - one of a group of two or more attached dwellings each being a building separated by a fire-resisting wall, including row house, terrace house, town or villa.

In line with QDC MP 4.2, a new house must:

• have a roof collection area at least 50% of the roof area or 100m² (whichever is lesser)
• be plumbed to service toilets, washing machines and at least one outdoor tap
• have a minimum capacity of 5,000L (1100gal) if the site has an area of 250m² or more
• have a minimum capacity of 45,000L in a rural zone and only where no reticulated water is available and connected in the rural residential zone.

In line with QDC MP 4.3, new commercial class 5-9 buildings: must:

• have a roof collection area at least 50m² of the roof area
• be plumbed to service toilets at 50m² per pedestal and outdoor taps
• have a minimum capacity of 1,500 litres per required pedestal.

The approval of mandatory rainwater tanks will be issued as part of the overall plumbing approval for any new residential or non-residential building(s).

Check the location of any Council sewers, stormwater or water mains on your allotment (refer to QDC MP 1.4). These may affect where you can site your rainwater tank.

Overflow from rainwater tanks needs to be discharged so is not a nuisance to neighbours or cause land erosion. Acceptable points for overflow discharge may include a bubbler 3m on downside of all buildings and 3m from property boundaries, or discharge into an existing Council-approved stormwater drainage system inter allotment/street channel.

Marking and signage

As well as the marking requirements (Clause 2.2 AS 3500 1.2003) the water supply system from a rainwater tank must be clearly marked at intervals and not exceed 500mm with the word "RAINWATER" in contrasting colour, in line with AS 1345. Water outlets must be identified as "RAINWATER" or with a rainwater tap identified by a green coloured indicator with the letters "RW". A typical sign is shown below.

Tank signage notes come from AS 3500 and QDC.

Plumbing approval requirements

When you install a rainwater tank, you must follow plumbing requirements.

To help install your tank, we've prepared four standard drawings. These drawings illustrate how to connect mandatory rainwater tanks the right way. 

1. Rainwater tank above-ground installation – trickle top up

2. Rainwater tank above-ground installation – automatic switching device

3. Requirements for mandatory tanks (below ground) on new dwelling – trickle top up

4. Requirements for mandatory tanks (below ground) on new dwelling – automatic switching device.

Building approval requirements

You need building approval for your rainwater tank if:

• the base diameter of your rainwater tank exceeds 3.56m
• the overall height of your tank exceeds 2.4m from natural ground level
• the base is greater than 5m in length
• a supporting structure (i.e. tank stand) is required and the overall height is over 2.4m
• an underground tank with an excavation of over 1m is to be installed
• the tank is mandatory (i.e. new building construction) on a block larger than 250m².

You will not need building approval in any other situations.

Follow guidelines on other related issues. These include where to locate the tank and how to discharge water overflow.

You need retrofit plumbing and building approvals if you install a rainwater tank on your property without the approvals in place first.

Retrofit plumbing approval requirements

A licensed plumber must follow the Form 4 process when carrying out the following work:

• connecting the rainwater into your home for toilet flushing
• connecting the rainwater into your home for cold water washing machine taps
• supplying the tank with a back-up town water supply.

The plumber must provide a filled and signed copy of Form 4 to the owner when work is complete.

We may audit the installation.

Internal rainwater connections

If you choose to connect your tank water internally, you need to:

• ensure the water supply system from the rainwater tank is clearly marked at intervals not exceeding 500mm with the word "RAINWATER" in contrasting colour
• install an approved rainwater sign above the tap on all external rainwater taps
• attach approved rainwater labels to all internal taps and rainwater points.

There are several options for town water back-up for internal fixtures.

A trickle feed top-up system

If rainwater levels get too low, this system adds a small amount of town water to your tank.

Automatic or manual switching devices

When water levels fall to a certain level, switching devices divert internal connections. The internal connections are between the tank and town water supply. The switch is located where the town water supply and rainwater tank meets the supply line. The switch is also located away from the tank.

A dedicated connection from the tank to the internal fixtures

When your tank’s water runs out, you’ll need to swap the supply over to an existing town water supply. This line should be inside your house.

Building approval requirements

You need building approval for your rainwater tank if:

• the base diameter of your rainwater tank exceeds 3.56m
• the overall height exceeds 2.4m from natural ground level
• the base is greater than 5m in length
• a supporting structure (i.e. tank stand) is required and the overall height is over 2.4m
• an underground tank with an excavation of over 1m is to be installed
• the rainwater tank is located within 1.5m of another structure (i.e. retaining wall)
• the tank is mandatory (i.e. new building construction) on a block larger than 250m².

You will not need building approval in any other situation.

Follow all guidelines on other related issues. These include where to locate the tank and how to discharge water overflow.

Tank overflow

Stormwater from a roofed area and any overflow from a rainwater tank must be collected.

Using one or more of the following techniques, the stormwater must be:

• discharged to the system of inter-allotment drainage
• discharged via an underground pipe to the street channel – all stormwater drainage pipework within the road reserve must be concrete, steel, FRC or Class 12 UPVC

Where the grade does not allow stormwater to be piped to a street channel, it needs to be discharged via an underground pipe. The pipe needs a bubbler outlet at least 3m from the downstream side of all building foundations. It must also be no closer than 3m to any property boundary so it causes minimum inconvenience to adjoining property owners.

Absorption trenches must also be installed a minimum of 3m from any downstream boundary.

You need a siting discretion approval if:

• the height of your tank including the supporting tank is 2.4m above ground level
• the tank is within 1.5m of any side or rear property boundary line.

You cannot place your rainwater tank in the 6m setback area from the property boundary line fronting a road.

If you're not sure what to do, contact a building certifier for help with siting requirements.

3 months

• Clean gutters and remove leaves and debris
• Clean first flush device/s
• Clean leaf guards on rainheads
• Check screen on tank overflow outlet

6 months

• Check roof and flashings for defects and remove overhanging branches
• Check tank for defects, screens and lids are in place and functional
• Check for signs of mosquitoes and larvae
• Check water is clear, has no taste or smell
• Check rainwater taps still have correct signage
• Check pump for noise, for appropriate pressures and for leaks
• Check acoustic enclosure if applicable

12 months

• Check tank support and if on a stand, check structural integrity of concrete slab

24 months

• Check sediment level in tank

We highly recommend regular inspection and if required, cleaning of your tank.

Gutters

Inspect and clean your gutters every 3 to 6 months. This is to make sure they're not jammed with leaves and other debris. If your gutters are full, we recommend checking them more often.

After a heavy rainstorm, check your gutters once the storm has passed.

Water can accumulate in low spots and contaminate and/or deteriorate your gutters.

Roof

Check and clear accumulated leaves, debris and other plant materials. If branches hang over your roof, prune them back.

Do not position your television antenna above the roof area that contributes water to your tank. Antennas attract birds, which increases the risk of contamination from bird poo.

Tank inlets, mosquito/insect proofing and leaf filters

Check, clean and repair your tank inlet when necessary.

Tank and tank roof

Check the structural soundness of your tank, including the roof and access cover. If you find holes and gaps, repair them right away.

Pipework

Check the structural soundness of your pipes. Make sure drains are not blocked.

Internal Inspection

If you find evidence of access by birds, animals, insects or mosquito larvae:

• find points of access and close them
• find points of light entry and seal them.

Check for any evidence of algae growth inside your tank.

First flush devices, rain heads and filters

To make sure they keep working well, check and clean these devices regularly. If required, repair or replace them.

Pump and pressure unit

Keep your pumps clean and ventilated. A quality pump and pressure unit should give you many years of trouble-free service, if you take care of it. Protect them from weather and corrosion as much as possible.

Cleaning out sludge

Check for accumulated sludge inside your tank every 2 to 3 years and clean it out if necessary.

When cleaning the inside of your tank, do not discharge the dirty water into a stormwater drain or onto the road. Instead, run the water onto your lawn and bury the sludge in your garden.

If there are large amounts of sludge, take it to the Waste Management Centre. Or get a professional tank cleaning company to do it for you.

Other maintenance considerations

Certain tanks may have specific maintenance considerations. For example, some tanks have a protective internal polymer coating that should not be damaged.

If you’re not sure, check with the manufacturer for your tank’s maintenance requirements.

Attaching some of these devices to your tank can help you get a constant flow of quality water.

Gutter guards prevent leaf litter entering your tank

When leaf litter enters and accumulates in your gutters, they block the rain head or inlet screen. This can cause overflow and reduce the amount of rainwater you collect.

Rain heads cast out leaves

Installing a screened downpipe rain head on each downpipe just below the gutter can cast out leaves. This rain head can prevent them from getting into your tank. We recommend the self-cleaning type.

First flush diverter redirects the first polluted flow

A first flush diverter will redirect pollutants and debris in the first runoff (20L/100m²) to your overflow drainage system. This will protect your tank from collecting too much sludge. It will also help reduce organic and chemical contamination.

For first flush devices to function well, they need to be cleaned on a regular basis.

Mosquito and insect screens keep bugs out

To keep the inside of a tank clean, mosquito and insect screens must be fitted. The screen gauze must have a diameter no larger than 1mm aperture mesh.

Filters provide additional protection

A variety of filters are available to protect your tank from:

• micro-organisms
• chemicals
• fine sediments
• colours
• odours.

We recommend these filters be replaced regularly so they can perform as designed.

Backflow prevention devices prevent untreated water contaminating the town's water supply

Check if there's an interconnection between:

• the town's water service
• the rainwater supply
• fixtures such as toilets
• appliances such as the washing machine.

If there is, you'll need to install an appropriate backflow prevention device. This will stop untreated water in your tank contaminating the town's water supply.

Roofing materials must not contain lead

Check your roof finishes and flashings.

Modern roofing materials are usually safe for rainwater collection. But some paints, especially on older homes, can contain lead. This lead can leach into tank water and cause contamination.

You cannot use lead flashings where rainwater collection is proposed.

Positioning of the tank outlet

Make sure your outlet is always above the base of the tank. This will help avoid drawing off the sediment that has settled at the bottom of the tank.

In line with Australian standards, the tap or outlet should be marked "rainwater".