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Installing a rainwater tank saves both water and money. A rainwater tank provides:
There are many things to consider before you purchase your rainwater tank, including size, placement location and installation costs.
1. Ensure you have a suitable roof material: Terracotta tiles, Colorbond steel, galvanised iron, Zincalume steel, fibro cement, polycarbonate or fibreglass sheeting and slate are appropriate options.
2. Think about the intended use of the water: Consider whether you want to use the water outside only e.g. in the garden or if you'd like an internal connection as well. An internal connection will require a plumbing approval. Read more about this below under the heading 'Plumbing approval'.
3. Estimate the volume of water required: Using Toowoomba rainfall records, a 10,000 litre (2,200 gallon) rainwater tank internally connected to the toilet and washing machine could be expected to generally supply 20-30% of the average daily water needs for a typical household. Using a 22,000 litre tank (5,000 gallon) would increase this figure to 30-40%.
4. Find a suitable location for the tank: When choosing a location for your tank, think of the areas in your house and garden where most of the water will be used. Have a look at the location of existing downpipes and decide if you can work with one of these. Ensure that once the tank is placed you will be able to service the tank and important areas of the home.
It's also a good idea to check that your tank placement won't block your neighbours natural light, ventilation and that noise from a tank pump won't be an annoyance.
If the rainwater tank doesn't fit in your preferred location research different tank shapes and sizes or consider placing the tank elsewhere. You can also choose to have an above ground or below the ground surface tank.
5. Check the best roof section for catching the water: It is important to consider the roof catchment area that can service the tank. Many installations use only about half the roof’s total area. Increasing the tank’s catchment is an effective means of improving the tank’s reliability of supply.
An easy way to work out how much water you may collect in a rainfall event is to remember that 1 litre of water = 1 square metre of roof area x 1 millimetre. This means that if you received 10 mi of rainfall then every 1 square metre of roof area draining to the tank will collect 10 litres.
6. Choose the tank material: There are many different materials now available at a range of prices. Check that the tank is manufactured to appropriate Australian standards.
Since 1 September 2014 we have required mandatory rainwater tanks and water saving measures on new dwellings and commercial buildings.
Queensland Development Code (QDC) 4.2 is now applicable to any new class 1 (a)(i)buildings (single detached dwellings) on blocks greater than 250m2. Dwellings on blocks less than 250m2 are exempt. Queensland Development Code 4.3 is applicable for any new commercial buildings (class 5 to 9).
Please note that 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.
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).
Ensure you check the location of any Council sewers, storm water or water mains on your allotment (refer to Queensland Development Code MP 1.4). These may affect where you can site your rainwater tank.
Overflow from rainwater tanks needs to be discharged so as not to cause nuisance to neighbours or erosion of land. 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.
In addition to the marking requirements (Clause 2.2 AS 3500 1.2003) the water supply system from a rainwater tank shall be clearly marked at intervals not exceeding 500mm with the word "RAINWATER' in contrasting colour, in accordance with AS 1345. Water outlets shall 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 as per Queensland Development.
There are a range of plumbing requirements which must be adhered to in the installation of mandatory rainwater tanks. To assist those involved in tank installation we have prepared four standard drawings (see bottom of page) illustrating the preferred means of connecting mandatory rainwater tanks. These are as follows:
Important note: There are health concerns relating to the drinking of rainwater. It is recommended that rainwater is disinfected. If you intend using rainwater for drinking, boiling is the most traditional form of disinfection. Ultra Violet (UV) under-bench disinfection systems are becoming popular. However, organic matter can coat the UV light and affect its operation.
Cleaning and maintenance of your tank is important. The following tips for cleaning and maintaining your rainwater tank are suggested: At least every 3-6 months, as the following describes:
Gutters: Inspect and clean making sure that they are free from leaf materials and other debris. If large amounts are found, then inspection and cleaning should be done more frequently, especially after heavy rainstorms. Gutters must be graded evenly to down pipes. Low spots where water accumulates not only deteriorate gutters but also contaminate the water.
Roof: Check and clear away accumulated debris including leaf and other plant materials. Overhanging branches should be pruned back. TV antennas attract birds and therefore should not be above the roof area that contributes water to your tank due to bird faeces contamination.
Tank inlets, mosquito/insect proofing and leaf filters: Check, clean and repair if necessary.
Mosquito and insect screens: These are required to be fitted to all inlets and outlets, and down pipes that hold water. The screen gauze must be a diameter not coarser than 1mm aperture mesh.
Roof gutter screens: To prevent leaf litter and other debris from blocking screens and collecting in the tank it is recommended that gutter guards be used.
Tank and tank roof: Check structural soundness of tank including the roof and access cover. Holes and gaps must be repaired.
Pipe work: Check for structural soundness. Make sure that drains are not blocked.
Internal inspection: Check for evidence of access by animals, birds or insects including the presence of mosquito larvae. Find and close points of access. Also check for evidence of algal growth. Find and close all points of light entry.
First flush devices, rain heads and filters: Check and clean and repair or replace if required. First flush devices need to be cleaned regularly to function well.
Pump and pressure unit: Keep pumps clean and ventilated. Protect from weather and corrosion. A good quality pump should give many years of trouble free service. Insist on a quality pump unit and pressure unit. Cheap units will be costly and disappointing in the long term.
Noise control: To minimise noise ensure the pump is designed with a minimum sound power rating and is housed and sited to minimise environmental noise impact. Submersible bore pump pressure systems are very quiet and can be used for tanks. This may eliminate the need for pump housing.
Overflow: Tank overflow pipes should be vermin proof and discharge in accordance with Council requirements.
Extraction point: The extraction point should be above the tank floor to ensure that water is of good quality. The bottom water zone is where particles settle and is anaerobic and often contains more micro-organisms.
Roofing materials: Most modern roofing materials are safe for rainwater collection but check on your roofing finish and flashings. Lead flashings must not be used where rainwater collection is proposed.
Inside of tank: Check for presence of accumulated sludge and clean out if necessary. Remember not to discharge dirty water into a stormwater drain or onto a road. Run the water onto your lawn. Small amounts of sludge can be buried in your garden. Large amounts should be taken to the Toowoomba Waste Management Centre. Alternatively, you can locate a professional tank cleaning company through the Yellow Pages. Certain tanks may have specific maintenance considerations. For example, it is important not to damage the protective internal polymer coating on certain tanks. Check with the manufacturer for your tank’s maintenance requirements.
A building approval is required for rainwater tanks where one or more of the following criteria applies:
In other circumstances you do not require building approval. However, you will need to follow guidelines on related issues such as where to locate the tank and how to discharge water overflow.
Figure 1 - Rainwater tank above ground installation – trickle top up
Figure 3 - Requirements for mandatory tanks (below ground) on new dwelling – trickle top up
Figure 4 - Requirements for mandatory tanks (below ground) on new dwelling – automatic switching device
Both plumbing and building approvals are required when retrofitting a rainwater tank on your property.
A licensed plumber must follow the Form 4 process when carrying out the following work:
The plumber must provide a copy of the Form 4 to the owner at the completion of the work.
We may audit the installation.
All plumbing work to connect your new or existing rainwater tank into the home toilet or cold water washing tap must be carried out by a licensed plumber. A plumbing Form 4 will need to be filled in and signed off by the plumber before being submitted.
If you choose to connect your tank water internally you will need to:
There are several options for town water back-up for internal fixtures:
Stormwater from roofed areas and overflow from any rainwater tanks is to be collected and discharged using one or more of the following techniques:
High quality tank water is dependent on the owner’s maintenance of a healthy tank. Proper maintenance involves the cleaning of gutters and down pipes and checking for mosquito and vermin control and installing tank water safeguards.
If water is only to be used for non-drinking purposes, such as in the washing machine or toilet, then it is unlikely that any treatment will be required, although filtering does limit some contamination.
If water is to be provided for other household uses that involve contact with humans, such as drinking, showering or cooking, additional treatment should be considered. Boiling is the most traditional form of disinfection, but ultra-violet under bench disinfection systems are becoming popular. However, organic matter can coat the UV light and affect its operation.
More information on using and maintaining rainwater tanks and potential water contaminants is available on the Queensland Health website.
Regular inspection of your tank is recommended.
Gutters: Inspect and clean; making sure that they are free from leaf materials and other debris. If large amounts are found, then inspection and cleaning should be done more frequently, especially after heavy rainstorms. Low spots where water accumulates not only deteriorate gutters but also contaminate the water.
Roof: Check and clear away accumulated debris including leaf and other plant materials. Overhanging branches should be pruned back. Television antennas attract birds and therefore should not be above the roof area that contributes water to a tank due to the risk of bird faeces contamination.
Tank and tank roof: Check structural soundness of your tank including the roof and access cover. Holes and gaps should be repaired.
Pipework: Check for structural soundness. Make sure that drains are not blocked.
Internal inspection: Check for evidence of access by birds, animals or insects - including the presence of mosquito larvae. Find and close points of access. Also, check for evidence of algae growth. Find and close all points of light entry.
First flush devices, rain heads and filters: Check and clean - repair or replace if required. First flush devices need to be cleaned regularly to function well.
Pump and pressure unit: Keep pumps clean and ventilated and protect from weather and corrosion. A good quality pump and pressure unit should give many years of trouble-free service.
Inside of tank: Check for the presence of accumulated sludge and clearn out if necessary. Remember not to discharge dirty water into a stormwater drain or onto a road. Run the water onto your lawn. Small amounts of sludgecan be buried in your garden. Large amounts should be taken to the Waste Management Centre. Alternatively, a professional tank cleaning company could be employed.
Certain tanks may have specifi cmaintenance considerations, for example, the protective internal polymer coating on certain tanks should not be damaged.
Check with the manufacturer for your tank’s maintenance requirements.
When installing a rainwater tank attaching several simple devices may assist in ensuring a constant flow of quality water.
Gutter guards prevent leaf litter entering the tank.
If leaf litter enters the gutter, this debris may accumulate and block the rain head or inlet screen causing uncontrolled overflow and reduce the amount of rainwater collected.
A rain head diverts leaves.
Installing a screened downpipe rain head on each downpipe just below the gutter casts out leaves, preventing them from entering the tank. Self cleaning types are recommended.
First flush diverter redirects the first polluted flow.
Pollutants and debris washing off the roof in the first runoff (20 litres/100 sq.m.) are redirected to the overflow drainage system, protecting the tank from excessive collection of sludge and subsequent organic and chemical contamination. First flush devices need to be cleaned regularly to function well.
Mosquito and insect screens are required to be fitted on all rainwater tanks.
The screen gauze must have a diameter no larger than 1mm aperture mesh.
Filters provide additional protection.
Various types of filters are available that protect against micro-organisms, chemicals, fine sediments, colour and odour. To perform well they need to be replaced regularly.
Backflow prevention device prevents untreated water contaminating the town water supply.
If there is an interconnection between the rainwater supply and the town water service supplying the outlet valve at fixtures and appliances, such as toilets and washing machines, an appropriate backflow prevention device must be installed to protect against the untreated water in the tank accidentally contaminating the town water supply.
Roofing materials may influence water quality.
Most modern roofing materials are safe for rainwater collection but roof finishes and flashings should be checked before a rainwater tank is installed. Some paints, particularly on older houses, may contain lead which could in turn leach into the tank water. Lead flashings must not be used where rainwater collection is proposed.
Positioning of the tank outlet.
The outlet should always be above the base of the tank to avoid drawing off sediment that has settled at the bottom of the tank over time. The tap or outlet should be marked "rainwater" in accordance with Australian standards.
