Porto Salvo: legally, a roof is not the surface of the ground in NSW, Victoria and Queensland. This legal position makes sense because people who occupy a building must have water and the roof provides it. In the other three states, the respective governments claim that there is no difference between a roof and a plastic sheet on the ground. In my opinion, this makes no sense. All governments regard water that falls on a plastic sheet on the ground as being surface water.

RObert: the SA, WA and Tasmanian governments claim rights to water that falls on your roof, however, if you choose to use that water - because they allow you to use it under law - this makes you liable. The other three state governments do not claim rights to water that falls on your roof and you are liable for it because you own it. Water that is collected on your roof becomes the government’s responsibility when it reaches the surface of the ground provided you have discharged it in compliance with government regulations. The public health issues have been resolved. You can use your rainwater for any purpose including drinking upon your own responsibility. You can sell it provided you meet food regulations. Your household plumbing can distribute both rainwater and mains water provided you comply with the Australian plumbing standard AS3500.1:2003, for purposes of backflow prevention.

Xoddam: spot on. With the benefit of large scale manufacture, distribution and installation, small rainwater tanks collecting water from most of the roof catchment area, can provide cheaper water than desalinated seawater or recycled sewerage but without a subsidy. Paying subsidies for uneconomic rainwater tanks is a waste of taxpayers’ money.

Liam: local councils buy wheelie bins in bulk and supply these to all ratepayers while recovering the cost from rates. Rainwater tanks can be treated the same but on a voluntary basis. People are likely to opt for rainwater supply when they compare the cost per kilolitre with the cost of desalinated seawater and recycled sewerage.

Greg Cameron gregorydcameron@bigpond.com

Greg

The cost with basic installation of a 7 000 L round tank on a concrete pad, level site, small pump, one tap at the tank, is $4 000. Connection to internal plumbing and provision of piping for (tank) overflows could cost that sum again, especially where installation is to an existing house.

How is this cheaper than buying the same water from the town supply?

Many homeowners are installing small tanks of around 3 000 to 5 000 L and such tanks would cut out quickly during the usual drier spells of the normal season. However, 5 000 L would not meet the needs of a small family for one week.

On the other hand, government planning for dams and infrastructure has not factored in the known population growth from migration. In view of both of these known facts, can you demonstrate the cost/benefit of government subsidising small tanks?

Finally, what homeowners are not told about small pumps is that they are triggered every time a tap is turned on. It is only the more expensive pumps that can maintain some pressure reserve.

The home designs of the past forty years and more are rarely suitable for water tanks and will in many cases compromise windows and access. Proposing many smaller modular tanks is fine in theory and great for profits but the cost to the householder, loss of yard amenity and access are downsides that must be considered.

Reintroduction of water tanks requires a revolution in house design. It also goes against the mainstream of town planning which is for more intensive housing in cities.

If governments expect some of the population to fork out large sums for water storage and to make greater sacrifices of yard amenity and use, it is reasonable to expect that these same homeowners should see some financial return on their investment through real savings in water taxes.

At the same time we should not forget that the homeowner has already paid his/her share of a dam and infrastructure through taxes on the development of his/her land and then again through higher rates.

The CSIRO has reported that a small decline in rainfall can make a very big difference to the amount of water available for consumption. Says CSIRO, in the last quarter of last century, a 14% decline in Perth’s rainfall reduced its water supply by three times this amount - by 52%.

But a 15% decline in rainfall has a minimal effect on the yield of a rainwater tank. Take Sydney as an example. With 15% less rainfall for the next 30 years, four 670 litre rainwater tanks collecting water from 175 square meters of roof area will yield 82 kilolitres each year for a total cost of $2975 or $1.21 per kilolitre. The cost per kilolitre in Melbourne and Brisbane is $1.40.

If you accept that mean annual rainfall will decline by 15% due to climate change, on this basis alone, rainwater tanks are a necessity.

Assuming mass production and distribution, the cost of a 670 litre tank is $150. The cost of a pressure pump is $150, automatic switching valve is $200, and delivery/installation/plumbing is $1200. Electricity costs $3.50 each year and four pumps are used over 30 years. Pressure pumps provide water at a volume and pressure that is similar to mains supply.

A precedent for the model we propose is your local council’s garbage collection service. The council purchases the wheelie bin which it supplies to households. Most councils provide the collection service using private contractors. Contracts are let by competitive tender. It is an efficient, proven, system.

There are 4.6 million separate houses in Australia that do not have their own rainwater supply (17% of houses have rainwater tanks). If each household purchased a rainwater harvesting system costing $2,365 per house, a multi-billion industry is created. This makes rainwater harvesting a numbers game, whereby a central agency can act as the bulk buyer to secure lowest cost for all Australian households. Every house in Australia can be supplied with a rainwater harvesting system within 10 years.

How is the cost estimate of $2,365 per household confirmed? Simple: call for expressions of interest.

(continued)
Cost estimates published by the National Water Commission for desalinated seawater are $1.73 - $1.98/KL and recycled sewerage $2.23 - $2.61/KL.

At these prices, why subsidise rainwater tanks?

A 670 litre rainwater tank is 80cm in diameter at the base and 150cm tall. Four of these tanks can be installed without occupying too much space, one per downpipe. Weighing 20 kilograms, this tank can be safely handled – and installed - by the householder themself.

Building regulations require water collected on a person’s roof to be discharged into downpipes connected to the stormwater system. They generally require one downpipe for each 60 square metres of roof.

When all downpipes are connected to a rainwater tank all roof water will be harvested. Tanks are linked by 25MM low pressure plastic water pipe.

An average Australian household uses 150KL of water indoors each year or 411 litres a day.

A house with 175 square metres roof area collects 175 litres of water for every 1MM of rainfall. It takes 2.4MM rainfall to yield 411 litres.

When rainwater tanks are full, tank capacity becomes available at the rate of 411 litres per day, or the equivalent of 2.4MM rainfall.

Tank capacity is maximised when an automatic switching valve is used to access tank water immediately it becomes available as a result of rainfall. Continuity of supply is achieved by automatically switching to mains when tanks are empty.

The 670 litre tank is bottom-draining which means it is emptied 100% of stored water.

All State Governments have clearly signalled that the cost of mains water will increase substantially when desalination plants are connected to the mains water supply.

Residents of New South Wales, Victoria and Queensland own the water that falls on their own roof. Consequently, the respective State Governments cannot make the use of rainwater tanks mandatory.

Would householders be happy to install rainwater tanks when the cost of this water supply per kilolitre was lower than the cost of the Government-owned water supply?

Why not ask them?

Greg Cameron

Greg, I cannot but applaud you for your article.
As to who owns the water the answer is; No one does!
As a “CONSTITUTIONALIST” I canvassed this issue extensively, when Victorian Premier Steve Bracks was making known he was going along with the 10 billion dollars project of the Federal government, so I wrote to him. Steve Bracks then quickly changed his mind alright!
Anyone who supports to give the Federal Government to have the legislative powers about WATER should have his/her head read!
The Framers of the Constitution extensively debated the WATER issue and concluded that “no one” owned the water. Surely, States have a limited power to regulate the water usage and as such the Commonwealth of Australia since Federation could legislate as to water usage of navigatable rivers to avoid lack of water for the navigation of boats, but only “reasonable” water usage.
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“Riparian rights” was much debated by the Framers of the Constitution also. As such it is all embedded in the Constitution.
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HANSARD 17-3-1898 Constitution Convention Debates
Mr. BARTON.-
Of course it will be argued that this Constitution will have been made by the Parliament of the United Kingdom. That will be true in one sense, but not true in effect, because the provisions of this Constitution, the principles which it embodies, and the details of enactment by which those principles are enforced, will all have been the work of Australians.
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Few people have a clue what the Constitution really stands for and time and again when I read judgments of the High Court of Australia and/or documents prepared by Professors of law I can quickly detect the utter and sheer nonsense they are stating.
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This post would not allow me to set it all out in details and some material can be found at my blog at http://au.360.yahoo.com/profile-ijpxwMQ4dbXm0BMADq1lv8AYHknTV_QH and my website at http://www.schorel-hlavka.com
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Being WATER or the Sunrays as they are natural elements that no one can claim as ownership. No government can control rainfall (don’t we know that) and their claimed rights over water are unconstitutional!

To add for clarity;
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Hansard 4-2-1898 Constitution Convention Debates (Official Record of the Debates of the National Australasian Convention)
Mr. WISE.-Each citizen is entitled absolutely to use all the water that falls on his own land.
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As to handing over legislative powers in regard of water to the commonwealth of Australia!
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HANSARD 24-1-1898 Constitution Convention Debates (Official Record of the Debates of the National Australasian Convention)
Mr. BARTON.-It would be the same as federalizing our lands.
Mr. OCONNOR.-It would, because the value of the land is inextricably mixed up with the value of the water supply to it.
Mr. HIGGINS.-All conditions would apply to lands; all circumstances affect their value.
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See further my article of 7 August 2007 on my blog