Brisbane’s newspaper the Courier Mail published an opinion piece by me today titled “Drip-fed figures“. I raised the issued of desalination. Is it an option for Australian cities?
Anyway, the piece begins: “Late last month Queensland Premier Peter Beattie announced $2.3 billion worth of new water projects � the water component of the 20-year southeast Queensland infrastructure plan and program worth $55 billion.
Interestingly, while environment groups generally campaign vigorously against new dams, they have been surprisingly silent on the dams and weirs proposed for the southeast. In fact there appears to have been little critical assessment of the water proposal at all.
The plan focuses on increasing water supply to accommodate the growing population, estimated to increase by a million people over the next 20 years. The program’s budget includes $149 million for Wyaralong Dam, $2 million to investigate desalination options and $23 million for “urban conservation initiatives”.
Curiously, the list of 23 projects comes to a total of only $861 million. It is unclear how the remaining $1.4 billion, to make up the $2.3 billion announced by the Premier, will be spent.
Furthermore, it is unclear how much water the different components of this plan will deliver. I am curious to know how much water the Wyaralong Dam might deliver relative to a desalination plant.
Perth and Sydney are now seriously considering desalination as an option. Certainly the water supply is assured whether or not it rains. The cost of desalination as a source of water is reducing dramatically with improved thermal and membrane technologies.
Globally, desalination capacity has increased at about 12 per cent per year over the past 30 years. There are now more than 12,000 desalination plants world wide, with about 20 per cent of these in the US. Australia is an island with most major cities situated next to the ocean, making desalination a real option for urban water supplies. …”
My friend Warwick Hughes is a member of the Perth Water User’s Group and they are campaigning against the proposed desalination plant for Perth. I gather they recently sent a letter to Senator Campbell that began:
Dear Senator Campbell,
URGENT: Perth water policy crisis
Your input or that of your Department is urgently needed to bring some scientific balance into the debate over Perth water supply options. Current WA Govt policy with respect for Perth’s water supply flies in the face of common sense scientific observations on rainfall, groundwater and rivers.
Current WA Govt policy is taking us down a path to a water supply increasingly based on water costing three to four times traditional sources. Already the WA Govt is constructing one completely unnecessary seawater desalination plant at Kwinana (with more to follow) to produce 45GL of water PA at an investment of $387Mill and rising.
All this waste of our money is taking place when there are several other vastly cheaper options available to enhance our water supplies.
Australia can not afford this huge and pointless waste which is making WA less competitive. ….”
So what do you think about desalination?
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
The huge advantage of desalination is that it is know to work – it will really deliver – and its costs are readily calculable.
By comparison, the alleged alternatives tend to be expressed in purely qualitive terms, with claims that they are cheaper not supported by any sort of detailed costing.
If opponents of desalination prefer other methods, let them provide the hard numbers to support their views.
Further, let’s stop treating water as if it were a limited resource. It’s just a commodity, with a price tag.
Sylvia Else.
Some questions:
Where do you get the power from?
How do you you deal with the salty effluent?
Water is limited by rainfall. You can desalinate but then you are limited by the electricity supply.
Many problems we face now are exactly because we treat resources as commodities and do not pay the full cost.
Warwick Hughes is asking even more questions than Ender at http://www.warwickhughes.com/sydwater/
and has written… “Right now I gather desalination proponents are preparing a report for the NSW Govt.
I wonder if they are mentioning the effect rising energy prices will have on future desal water cost.
I wonder if they are pointing out that as soon as water is made in factories there will be water strikes.
Is anyone preparing a rational view of alternatives ?”
But I am, nevertheless, optimistic about the prospects/the future including new sources of energy.
Dear Jennifer,
Sure as desalination technology has improved this has lead to more plants being built. Another big driver must be the huge wealth transfers post mid 70’s to oil producers many of which have very dry climates, which has given them the capacity to spend big on water.
You mention a statistic that there are ~2400 plants in the USA.
It would be interesting to have some idea of the ranges of capacity, how many are in fact quite small, how many are treating seawater and how many brackish water and how many providing substantial portions of municipal water supplies for communities with 600mm or more of “run off” rainfall per year.
Speaking about Perth, we have never had a “debate about seawater desalination” as opposed to our traditional mix of supplies.
In what I can read about the Sydney response to low dam levels at a time of reduced rainfall (no worse than periods in the last 100 years), I see many parallels with Perth. Politicians being lead to accept a misleading picture of rainfall with the help of CSIRO climate model predictions, no doubt huge secret efforts by the desal and construction companies in secret, telling policymakers who knows what.
Nobody speaking about rainfall history realistically in context.
Amazingly in SW WA for example there is no peer reviewed study of all rain data and the same would be true for Sydney.
I have just put up new web pages on the Sydney water issue;
http://www.warwickhughes.com/sydwater/
There is a ref to submissions to the WA Govt ERA water price inquiry. An inquiry foisted on the WA Govt by Fed. competition policy, an inquiry which has recommended the Kwinana Desalination Plant (KDP) be postponed. Those submissions set out where Govt policy is ignoring three areas where water supplies could be easily and cheaply augmented on a scale of the KDP.
Thats enough for now.
Warwick Hughes
Perth is simultaneously tackling it’s water problems in a number of ways.
A well understood method is forest thinning. A 12,845ha catchment is proposed to be thinned over the next few years to increase stream flow into an existing dam. The project is currently subject to environmental review.
Benefits include low cost per kilolitre and better utilisation of existing infrastructure, it will be a carbon neutral operation (for those of us who are concerned about CO2), and it promotes effective active management of regrowth native forest and grow more wood (if we’re allowed to harvest it). If it’s successful, then the same treatment could theoretically be applied to the other regrowth forested water catchments supplying Perth and the sw of the state.
See http://www.watercorporation.com.au/wungong/ if you’re interested.
I thought the Water Corp was also investigating other underground sources of water, but because these are remote from the city, they are more expensive than current water, and not a lot cheaper than desalination at the city.
Desalination – the power will come from the grid, though the Water Corp was reported in the media as considering installing sufficient wind generator capacity to offset the coal-fired energy.
Salty effluent is piped back to the ocean. I think the quantities are relatively small and dispersal is considered okay by the proponents. The volume of effluent is about the same as the volume of fresh water produced (?).
Electrical energy is effectively only limited by cost, even including the environmental costs. There are several carbon-neutral sources of electricity but they are still comparatively expensive. Wind is about twice the current cost of coal fired power in WA. I don’t know what the cost of desalinated water would be if the cost of electricity was doubled (e.g. using only wind power), but it wouldn’t double the cost of the water. As desalination will always be only one of several sources, doubling the cost of the energy for desalination would have a very modest effect upon the cost of all water for the city.
It’s not the whole solution, it’s more about not storing all your eggs in the one receptacle.
Warwick,
Thanks for the interesting comment post.
Re. Desal in the US: I have not been able to find a comprehensive list of desal plants in the US including how much water they produce and from what sources. If a reader of this blog can provide a link or reference it would be great.
There is a fair amount of information for some states – including Florida. I find it tedious converting from their I think it is MDG which equals mega gallons per day to something that makes sense to me i.e. gigs per year.
But anyway they are producing a fair percentage of their water from desalination of aquifer water which had been ‘lost’ to salt water intrusion. And I guess your point is that this would be a lot cheaper from an energy perspective than making freshwater from seawater as proposed for Perth?
Instead of an de-salination plant how about an agressive greywater re-cycling scheme that subsidises people to install greywater and rainwater tanks. Instead of building new water schemes how about we use the water we have more wisely.
Electrical energy is not only limited by cost. That is a economic view that wrong. Electrical energy is limited by the fuel used to generate it. If coal is used then we will not be able meet CO2 reduction targets. Gas is ultimitely limited by supply – even though the supply seems huge at present it will peak at some stage and force us into another crisis. And it still releases CO2 – less than coal true. Nuclear power is out of the question. Renewables need us to reduce power consumption. Building de-salination plants will only put more pressure on already overloaded power system and make it harder to swith to renewable power in the future.
In economics you are always told to live within your means. We need to do the same with water.
I agree with you in most regards Ender. However the cost of even simple technology can be quite high. E.g. the sort of rainwater tank that would fit into a typical suburban garden would store perhaps 10 kilolitres and be insignificantly small compared to typical annual consumption of about 300kl per year. In Perth’s mediterranean climate, this sort of tank would be a only a few day’s supply when the summer drought sets in and cost about 3 times the annual household water bill for the tank alone. Then there’s a pressure pump, plumbing the roof gutters into the tank etc.
Grey water is more promising I think because the house continually produces the supply and reuse reduces the use of drinking water on the garden. Recycling on a large scale seems unlikely to me because of the high cost of duplicating the sewage system for central collection of grey water. Storm water from roads must be worth analysing if it can be stored cheaply enough. Big if; maybe inject it into aquifers for later withdrawal.
There are large-scale base-load renewable options for energy such as geothermal and biomass. Cost is a problem (similar to wind power), but renewable energy doesn’t have to mean solar panels on the roof, which is still an economic joke, unfortunately.
I list comments in chrono order headed by the contributor and date, without repeating what was originally said to cut down on length of this post. Obviously some of what I say applies to more than one persons post, eg the URL’s just below..
Sylvia Else at May 18
A quick look on the internet brings up examples of failed desalination plants, legal disputes and cost over runs, there is a risk with new technology.. Let’s hope they are improving their game. Some URL’s that suggest desalination is no bed of roses.
Yuma desal plant on Colorado River, fairly old seems to be MOTHBALLED.
http://www.usbr.gov/lc/yuma/desalting/default.htm
Many adverse comments, judge for yourself
http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2004/07/21/BAGN17Q00V1.DTL
Critical of Tampa Bay
http://www.hotpolitics.com/desal1.html
Santa Barbara water authority, desal plant in MOTHBALLS
http://www.ci.santa-barbara.ca.us/departments/public_works/water_resources/bfsupply.html
US Army Corps of Engineers cost estimates, page does not look recent but costs look on scale. Contrasts brackish water vs seawater costs.
http://www.oas.org/usde/publications/Unit/oea59e/ch20.htm
Widespread desal of groundwater in southern Florida
http://www.whoseflorida.com/misc_pages/membrane_filtration_plants.htm
Already the Kwinana Desalination Plant (KDP) cost has blown out from $346Mill to 387 and the first sods are just turned.
From at least Roman times mankind has used dams to store water, can we accept that with rare exceptions dams work well ? Getting a water bill periodically and a read of annual reports of our water utilities will quickly show you that the cost of our water supplies is known too. And it is vastly cheaper than water by seawater desalination.
Ender at May 18
Water from rainfall is vast Ender, sure it varies a lot but we can understand that better by studying rainfall history.
Perth dam catchments have ~3000GL falling into them each May to October wet season, near 10 times Perth consumption. Of this huge resource last year we left over 97% for the “environment” because Govt chooses not to upset the Greens by managing catchments.
In my opinion Ender “many problems we face” are due to at least 20 years in which our scientists & engineers have failed to rebut or subject to critical scrutiny unscientific Green dogmas and now we see these emerging into policy, with multi-$Billion costs on us all.
Rick at May 19
This Wungong project involves only 3.8% of Perth catchments so my point is that it is “fiddling while Rome burns”. The Govt land manager CALM and WaterCorp know exactly what to do but the Govt chooses not to get this low impact win, win, win program underway on 100% of catchments for fear of alienating Green preference votes.
I am not aware of any proposal to apply “catchment management” to “the sw of the state”. I think it would only be relatively small areas where the various communities have local supply catchments, see my page on Manjimup water issues;
http://www.warwickhughes.com/water/manjimup.html
Unfortunately, windmills with the huge taxpayer subsidy only make power when wind blows so you still need backup coal fired grid capacity.
Re “salty effluent” not so Rick, the discharge is 65GL pa (180ML/day) at 65,000 parts saline (seawater is ~35,000). Sure the proponents say dispersal is no problem but WaterCorp is only TODAY presenting public material on new modelling of the discharge after widespread disquiet at the rubber stamping of the project by the EPA in Sep 2002. The point here is that Cockburn Sound is partly enclosed and university experts have expressed concern that the ultra saline discharge which is heavier than seawater, will buildup on the bottom leading to stratification and less oxygen for biota.
No doubt their new reports, costing ? ~$250,000, will say all is well.
I note that for subsequent plants WaterCorp plans to pipe the ultra saline outside the Sound to the ocean coast near Rockingham. Natural ultra saline waters from Shark Bay near Carnarvon, are identified 200 kms out on the ocean floor. Dispersal ?
Perth does not have all its eggs in one receptacle.
Perth has the dams, installed by far sighted earlier generations, rapidly being decommissioned by a lack of catchment management. see graphic in our ERA submission.
Perth has huge local groundwater reserves.
Perth rivers nearby, taking the Avon, Murray and Collie, 680 GL of water (twice our annual consumption) runs to sea each year only 13% as saline as the sea.
For more info on Perth’s 3 areas of neglected water resources see Perth Water Users (PWU) 6 May ERA submission. PWU sets out point by point how WA Govt mismanagement of Perth water resources is at the root of our so called “water crisis”. PWU illustrated 6 May submission to the ERA Inquiry on Urban Water and Wastewater Pricing – can be read on pdf file at http://www.era.wa.gov.au/water/content/waterInquiry/default.cfm
follow link under heading Submissions, to “Draft Report Submissions New!”; for our September 2004 3 page pdf submission click on “Issues Paper Submissions”.
Ender at May 19
I agree with Rick that promoting household water tanks (unless they are v big)is expensive and many could turn to health hazards, mozzies etc with neglect.
Use of greywater I think can only work with dedicated people. If an “agressive” mass program is foisted on us there will be mismanagement and health issues, the stuff stinks v quickly.
We have lost sight of the fact, unlearned as I say, that cheap municipal water for the masses evolved in the 19C and was one cause of greatly reduced mortality. Why are we turning away from such a roaring success ?
Because we have been suckered into listening to unscientific Green propaganda.
I live in Perth also however anything is better than nothing. The problem is that there is no incentive for people other than environmentally committed people to do it – this is what we need to change.
Solar panels on the roof are good as they are a local source of power. When electricity cost is calculated what is ususally left out is the massive cost of the distribution lines and the cost of the army needed to maintain them. Local power avoids this. If in the future an electric car can be a part of this then households will be less dependant on central power plants.
Late response.
Thanks Warwick. I didn’t mean to imply that there are plans to thin all the forested water catchments, rather that there is no reason why we shouldn’t. The data has been around for some years; it is just sensible land management. However I see Wungong as interesting partly because as a first tentative step, it is the Water Corp who are running with it. CALM has become a shadow of its former self, but I deny having said that.
Ender, the solar panels cost about $20,000 per household (?), I may need to be corrected. At a modest rate of 7% for the cost of finance (or opportunity cost of available cash), solar panel finance costs more than your annual power bill and I haven’t allowed for maintenance yet. About a third of the cost of your Western Power electricity is the cost of distribution, so the savings here are modest for local generation. If you have main grid backup to your local source, there is no savings from distribution because the capital cost of the system is still there. Also, the more local generation there is, the more costly management of the main grid becomes because juggling all the inputs and outputs becomes complex and potentially very unstable. Particularly if local generation is predominantly solar, because all the panels on all the city’s roofs shut down and fire up in unison.
Analogy is Denmark with 20-something percent wind power. This is only feasible because there is a huge nuclear power grid in Germany which provides stability for the Danish grid, which would otherwise wobble and fall over.
Rick – That is true with our present grid tuned to large central power stations. A new model is intelligent local nodes actively managing all the elements. We still have a grid that depends on large 24X7 power because that is the way it always has been done and to all involved this is the only way it can be done.
First in Denamark there has been no real attempt to dramatically reduce demand. Any move to renewable power MUST start with 50% reduction in demand that can be achieved with efficiency gains and reduction in use. Also widely dispersed renewable energy sources will not all go out at the same time.
In the future grid electric cars and pluggable hybrid cars will play an important part in the storage of power for times of fluctuations. Modern AC drives can supply power to the grid when plugged in for re-charging.
Also there just might have to be the realization that 24X7 unlimited electricity is costing us the Earth and may not be sustainable in the long term. Nuclear power is only putting off the damage to later generations who have to deal with our waste in some fashion. We really only wrap it up enough so that we are long dead when it becomes a problem.
OK, I’m going to let a element of ranting creep in here.
Some of the foregoing posts are exactly the sort of thing I’m talking about. Rainwater tanks? Have you calculated their cost? Have you even estimated the amount that could be captured from all the roof space in Sydney (it’s not enough)?
Power requirements for desalination. Yes, it needs power. So calculate how much. Then consider moderately oversizing the desalination plant, and running it outside peak power consumption periods. It you do the sums, you’ll see that it can easily be run off the existing power infrastructure.
Grey water? Did you look at the distribution issues? Installing all that new pipework isn’t cheap. This is not the most economical option, for sure.
Transmission costs for electricty not being included? Yes they are, as you’d know if you’d bothered to do the research.
Solar panels? You have to be joking, surely. Don’t you know that it takes years just for them to generate as much power as was used in making them? They cost a fortune to make. Generating power that way only makes sense if you have no other option.
Salt water effluent. Yes, it will have an impact on the environment. Pretty much everything we do does. I can’t imagine that all that fresh water sewage is that palatable to life used to salt
water either. Perhaps we could mix them together?
Anyway, life is hard, and most creatures die before they reach maturity. It’s a killing field out there, you know? A bit of salt water is the least of their worries.
As for cost overruns, and other legal disputes over desalination. So what? Some people can’t even get their house repainted without getting into difficulty. Stuff like that happens. You wouldn’t suggest that house painting is risky would you?
FWIW, I did a rough costing for desalination for this thread:
http://www.naturistlp.org.au/forum/viewtopic.php?t=20
Sylvia – in power comparision costs between differing power sources that tranmission cost are excluded. The final price to the customer includes all costs however this is rarely the figure used to calculate the cost of electricity.
Grey water and rainwater saves water. The more you use re-cycled and captured water the less you use of distributed water lessening demand. Really you are saying lets desalinate heaps of sea water so we can go on wasting as much as we want. We should first use the water we have wisely and treat it like the precious resource it is in the driest continent on Earth.
Solar panels take between 2 and 4 years to pay back the power however they can generate power for 20 or 30 years. How many options do we have if we want to reduce CO2.
For desalination plant to work efficiently there is not the option to turn them off when the power peaks – they need to work 24X7 so your scheme of only using them at peak time will not work. How do we generate the required power??
Your comment about life being hard pretty much sums up your attitude to the environment. Again I am not against desalination however we should do much much more toward using what we have FIRST before going down this path. If we conserve first the required desalination plant will be smaller, cheaper and require less power to run or we may find we can do without it.
Conserving first is win-win situation.
The consumer wants two things where they turn on the tap. Firstly, that water comes out, and secondly that it costs them no more than it needs to.
Sydney’s water deficit is around 50% – that is, over the last six years, it’s used twice as much water as has been captured. The only possible solutions involve decreasing consumption, and increasing supply. These are direct alternatives to each other, so you adopt whichever is cheaper.
Rainwater capture is surprisingly expensive – much more so than desalination. I looked at installing tanks at home. The numbers just didn’t add up. Recycled water is fine when it is put in place for a new suburb, but the costs of retrofitting it to existing suburbs would have to be huge (digging up every residential street in Sydney?).
Desalinators have a high capital cost, and running them less than 24×7 increases the effect that that has on the price of water, but this is somewhat offset by the savings on peak time electricity. Sydney’s desalinator would require a few hundred MW. There is ample capacity in the system to provide that for 18 hours a day. Look at http://www.nemmco.com.au/ (the wholesale electricy market) if you don’t believe me.
Sustainable power generation is a separate topic, but solar cells don’t make the cut. They cost too much. There are cheaper ways of generating power sustainably, so you don’t use solar cells. Wind power is established, if not exactly cheap. Geothermal (‘hot rock’) technology is looking very promising, and has the added advantage of being reliable, in the sense that it’s not dependent on things we don’t control like the wind.
As for the environment, we need to avoid wrecking it, but that doesn’t mean we won’t change it. We do that just by being here. Have you checked the biodiversity under your house recently?
Sylvia Else.
Wave Power
Earlier this year, the Queensland and federal governments offered Toowoomba City Council $46 million towards the cost of a proposed $68 million Toowoomba waste water recycling scheme.
Ratepayers rejected the proposal by a majority of two to one.
Based on advice from Toowoomba City Council, the federal and state governments rejected rainwater tanks as an option for increasing the region’s drinking water supply, on grounds of cost and yield.
The council estimated the cost of retrofitting a rainwater tank to an existing house is $5000 and the yield is 25KL per year.
In fact, rainwater tanks can be fitted to all existing houses in Queensland for less than $3000 per house to yield up to 80KL per year in Brisbane – 60KL per year in Toowoomba – in the current drought.
If all houses and all buildings in southeast Queensland were using rainwater tanks now, they would have provided 100 billion litres of water in the last 12 months (3 billion litres in Toowoomba or 30% of current use).
Should rainfall return to a more normal pattern, rainwater tanks can provide about 130 billion litres each year in SEQ (4 billion litres in Toowoomba or 40% of current use).
The achievable yield from rainwater tanks compares with 46 billion litres each year from the proposed Tugun desalination plant, or 70 billion litres each year from the proposed Mary River dam.
The Queensland and federal governments accepted Toowoomba Council’s estimate of rainwater tank cost and yield.
No further consideration was given because, under clause 2 of the National Water Initiative Agreement signed by the Queensland government, rights to the use of water in Australia are vested in governments.
The Queensland Water Act 2000 says–
19 Rights in all water vests in State
All rights to the use, flow and control of all water in Queensland are vested in the State.
“Water” means–
(a) water in a watercourse, lake or spring; or
(b) underground water; or
(c) overland flow water; or
(d) water that has been collected in a dam.
“Overland flow water … does not include water collected from roofs for rainwater tanks”; “the term [dam] does not include a rainwater tank”.
Did the Queensland government advise the federal government that all rights to the use, flow and control of water collected from roofs for rainwater tanks in Queensland are vested in the State?
What has occurred in Queensland is that rainwater tanks are mandated for new houses but not existing houses. What did the government want to achieve by excluding existing houses?
Will the Queensland Government accept that rainwater tanks can be fitted to existing houses in Queensland for less than $3000 per house to yield up to 80KL per year in Brisbane in the current drought?
The government has the ability to make rainwater tanks a building fixture of all buildings in Queensland at point of sale.
Here’s why it should.
Brisbane received 931mm rainfall in the 12 months to 13 September – one of the lowest rainfalls experienced in 100 years.
An average house with five one kilolitre rainwater tanks collecting water from the whole roof area (all downpipes) for hot water, laundry and toilet flushing, would have obtained 80KL of water – enough for one-half of indoor water use for the year.
Southeast Queensland’s population is projected to increase by 52% from 2.38m to 3.61m by 2032 (ABS).
The number of separate houses in SEQ will increase from 700,000 to about 990,000 by 2032.
If all houses use rainwater tanks they will provide 79 billion litres of water each year in 2032.
If all houses plus all other dwellings and all buildings use rainwater tanks, they will provide about 100 billion litres of water each year – based on the current drought persisting for 25 years.
If an additional 1.23m people each uses 250 litres of mains drinking water a day – the Queensland Government has set a target for reducing per capita mains drinking water consumption in SEQ from 300 litres per day in 2005 to 250 litres per day in 2020 – the increased demand will be 112 billion litres each year.
Should rainfall return to a more normal pattern, rainwater tanks can provide about 130 billion litres each year in SEQ.
Rainwater tanks will be able to provide between 100 billion litres and 130 billion litres of water each year in 2032, when the demand for water will have increased by 112 billion litres due to population growth.
The state government currently pays SEQ houseowners a subsidy of $1,000 for installing and plumbing rainwater tanks.
The subsidy fund is capped at $84m which means that 84,000 houseowners are eligible. This is 12% of all houses in SEQ.
If all SEQ’s houses installed a 5KL rainwater system, the cost would be less than $3,000 per house – without the subsidy.
The cost of rainwater is $1.65/KL (capital cost of $1.25/KL and operating cost of $0.40/KL) based on the current drought continuing for 30 years.
Under more normal rainfall and based on annual yield of 100KL, the cost of rainwater is $1.35/KL (capital cost of $1.00/KL and operating cost of $0.35/KL).
This low cost is guaranteed because of large economies of scale in manufacture and installation (including plumbing).
Queensland state government policy throughout the 20th century was to remove rainwater tanks from urban areas.
Only 5% of Brisbane households now have them (15% in Toowoomba).
In hindsight, this was a policy mistake, but fortunately it can be easily rectified.
The government can require rainwater tanks to be a fixture of all buildings at point of sale.
This does not affect the building owner’s legal right and entitlement to use their own rainwater for domestic purposes as a matter of free choice.
All new house owners will benefit from lower costs if rainwater tanks are a mandatory building fixture for all houses at point of sale.
Houses change ownership on average every seven years.
Installation at point of sale allows for easiest financing and at the lowest possible cost.
As a once-off expenditure, rainwater tanks are less than one per cent of the cost of an average house in SEQ.
Rainwater tanks do not preclude other supply options, such as stormwater and waste water recycling, or desalination.
Rainwater tanks also benefit the environment. Water discharged from roofs into the stormwater system is damaging to the environment because it is concentrated at the point of discharge and has considerable, destructive, velocity.
How is it possible to install five KL of rainwater tank capacity into a confined house block?
One way is to have five 1KL rainwater tanks in the shape of a D. Looking from the top down imagine the D shape being flat on the ground.
These tanks are useful because they are low cost, simple to install and occupy little space (because they fit beneath the eaves).
The tank’s flat back is positioned flush to the exterior wall.
It is 2m high and 800mm in diameter – therefore the round shape protrudes 800mm from the wall.
This means that D-Tank fits neatly under the eave of a house.
A 650L version is 1500mm high with 800mm diameter.
In reality, one tank can be installed on each of three walls of a house with two tanks installed on the fourth “dead” wall.
The tanks are interlinked by 20mm pipe.
For slab houses, the pipe follows the base with a cover plate.
For a stumped house the pipe runs underneath the house.
The tanks gravity feed to the lowest point where there is a pressure pump installed.
Transfer of water between tanks is also assisted by the pressure pump.
D-Tank’s base height is adjustable to provide the gravity feed.
The tank does not require a concrete base.
D-Tank is bottom draining and it is dry when empty.
D-Tank can be made with injection moulding at the rate of one tank every three minutes.
This provides for absolute lowest cost with highest volume. All houses in Queensland could be supplied from just several machines.
There are no rainwater tanks made in Australia using injection moulding.
(Square 1KL tanks are currently made by blow moulding in Melbourne. These tanks are used for industrial liquids.)
D-Tank weighs 40KG and can be installed as a do-it-yourself item (a further cost saving) or by a single installer.
Plumbing and electrics still require a certified tradesperson.
An switching valve has an LED display which allows the householder to know whether the water supply is mains or rain.
The valve and pump can be set to a timer so that mains water is used at selected times, if required.
The system is fully automatic and requires no further attention by the householder once installed.
The electronic control technology is capable of wireless communication.
The Australian plumbing standard AS3500.1 provides the requirements for connecting a rainwater tank to the mains drinking water supply.
It is a matter of personal choice if the rainwater is also used for human consumption.
Councils may not refuse to approve plumbing applications that comply with AS3500.1.
A person who plumbs their rainwater supply into their drinking water supply can do so for whole of house use; or for restricted use, such as hot water, laundry and toilet flushing. They do not have to drink rainwater if they choose not to.
There are no regulations in Queensland which require water collected from roofs for rainwater tanks to comply with the Australian Drinking Water Guidelines.
If every building in Australia substituted rainwater for mains water the yield would be more than 500 billion litres – enough water to supply Melbourne.
Surely rainwater tanks are a water resource of national significance?
With a national approach implemented at the local level, rainwater is a cost-effective source of water supply for all of Australia.
gregcameron@kooee.com.au
Greg Cameron posts some interesting figures.
However, there are some questions and comments.
Please show quotes to actually connect a tank system that can yield 80Kl per annum to a house for $3000, with pressurised water.
If the tanks referred to are the 5 * 1 Kl tanks later mentioned, how do 5 1 Kl tanks collect 80Kl/annum….sorry ….”up to” 80 Kl? Or is this simply based on roof area? It has to be born in mind that a house of 150 m2 need only receive 30ml of rain to fill that 5 Kl of tanks. After that, the water goes back to waste. Queensland _may_ have the weather patterns to then refill those tanks to match usage all year round, without either overflowing or becoming empty.
At the _claimed_ $3,000 per installation and 80Kl per annum each, with the _claimed_ yield of 130 billion litres each year, that is 130 Bn / 80K installations * $3000 each = $5 bn….a rather expensive exercise. The tanks will probably last 20 years at most, so this is equal to $250,000,000 per annum for maintenance.
Then there are pumping costs and the maintnenace of the pumps.
please send me any inforamtion about water desalination