Water Miles
This website is a way of promoting water miles and related concepts (peak water and virtual/embedded water). It also serves as a reference for water and energy-related references. We need to recognise that we are becoming water and energy constrained (at the same time). Old solutions to water shortage involved increased energy use, which is not sustainable. Even where water is not short, water use is energy use. The water miles concept is a way to conceptualise this fact.
Please see the categories on the right hand side bar, which represent an attempt to sort through the growing list of posts, to make their retrieval easier. I hope you find something of interest. Please post your comments!
Greymatters – new greywater information portal
Greymatters is a website designed to be a single point of reference for all matters concerning greywater reuse including:
- current information about what is required to safely and sustainably divert, recycle, re-use and apply greywater to land,
- current best practice guidelines and advice,
- national & international guidelines and policy,
- research reports peer reviewed scientific publications,
- technical advice providers and service suppliers, and
- information on the latest research.
Onsite wastewater compared with centralised wastewater
The latest edition of Trim Tab (the magazine of the International Living Future Institute) has an article which compares conventional centralised wastewater systems with on-site systems (based on an LCA). Passive on-site systems, such as constructed wetlands, have much lower impacts, whereas more intensive on-site systems, such as membrane bio-reactors, have higher impacts.
Here is the full LCA.
Water footprint newsletter
First “Global Water Footprint Standard” Training Course
Registration is now open for the first Global Water Footprint Standard Training Course that will take place 10-12 May 2011 in Amsterdam. After concluding this course, participants will receive the Certificate of the Global Water Footprint Standard Training Course, which provides proof in the market that the individual holding the certificate is acquainted with the global water footprint standard. The certificate is stamped by the Water Footprint Network.
Ensure your participation by registering now:
www.waterfootprint.org/downloads/GlobalWaterFootprintStandard-TrainingCourse-May2011.doc
Play the River Basin Game!
The University of Twente developed a computer-supported classroom game that illustrates various phenomena that take place when farmers compete over water. With whatever group you play, it’s always fun and a great learning experience. Download the river basin game – for free: http://www.waterfootprint.org/?page=files/Riverbasingame
Green-blue-grey water footprints of products
Statistics on the green, blue and grey water footprints of a wide variety of crop and animal products are now downloadable in Excel-format. Data are given per country and province/state for all countries of the world. Download data from:
http://www.waterfootprint.org/?page=files/Productwaterfootprint-statistics
Available books on water footprint
* Virtual water: tackling the threat to our planet’s most precious resource (2011)
by Tony Allan – www.ibtauris.com
* The water footprint assessment manual: Setting the global standard (2011)
by Arjen Hoekstra et al. – www.waterfootprint.org/?page=files/WaterFootprintAssessmentManual
* Corporate water strategies (2011)
by William Sarni – www.earthscan.co.uk/?tabid=102569
* The green blue book (2010)
by Thomas Kostigen – www.thegreenbluebook.com
* Water footprint and virtual water trade in Spain: policy implications (2010)
by Alberto Garrido et al. – www.springer.com/economics/agricultural+economics/book/978-1-4419-5740-5
* Globalización del agua: Compartir los recursos de agua dulce del planeta (2010)
by Arjen Hoekstra & Ashok Chapagain – www.marcialpons.es/fichalibro.php?id=100880180
* Globalization of water: sharing the planet’s freshwater resources (2008)
by Arjen Hoekstra & Ashok Chapagain – http://eu.wiley.com/WileyCDA/WileyTitle/productCd-1405163356.html
More information
Website: www.waterfootprint.org
Contact: info@waterfootprint.org
Global Water Footprint Standard Launched
Water Footprint Newsletter
Today, the Water Footprint Network launches the Global Water Footprint Standard. This standard is contained in a new book:
The Water Footprint Assessment Manual: Setting the Global Standard
Download from: www.waterfootprint.org/?page=files/WaterFootprintAssessmentManual
The standard receives a lot of international support. Read today’s media release here below:
Media release
International Leaders Support Global Water Footprint Standard
The first Global Water Footprint Standard, a scientifically credible methodology that will make all water footprints comparable, has garnered international support from major companies, policymakers, NGOs and scientists as an important step toward solving the world’s ever increasing water problems. Developed through a joint effort of the Water Footprint Network, its 139 partners and scientists of the University of Twente in the Netherlands, The Water Footprint Assessment Manual: Setting the Global Standard clearly demonstrates how individuals, companies and nations can quantify their contribution to water use conflicts and environmental degradation in river basins around the world.
The water footprint – the amount of freshwater used in the goods and services consumed or used in production – is helping companies to reduce water use where it is most wasteful, banks to assess water-related risks prior to making investments and governments to improve water management. Individuals can use the water footprint to understand how much water they are using through the food they eat, the clothes they wear, the consumer goods they buy. Changing to less water intensive products and choosing to buy goods from water rich areas or catchments that are sustainably managed will move them toward a sustainable water footprint.
“The water footprint of common products such as coffee can be surprising, for example it can take an average of 140 litres of water to produce each cup of coffee, but more importantly, the Global Water Footprint Standard helps us all know more about how much water we use, where it comes from and how we each can take steps to make our water footprint sustainable, to ensure that the world’s people and natural ecosystems will have the freshwater necessary to thrive well into the future” says Ruth Mathews, Executive Director of the Water Footprint Network.
Partners from business, civil society, government, global institutions and academic organizations are working with the Water Footprint Network to push for improvements in water use efficiency, pollution reduction and sustainable water management. As more pressure is put on freshwater resources, using the standard in all sectors and in all river basins will be increasingly important. The publication of this standard helps individuals, businesses and governments take steps toward a sustainable water footprint.
Strong and Credible
“Water is vital to business: poor water quality or insufficient supply can curtail – or even shut down – activities in business operations and in the supply chain. The method laid out in the Water Footprint Assessment Manual fills an emerging and urgent business need for a means of understanding water consumption in operations and in the supply chain, assessing its sustainability, and devising effective response strategies.”
Monika Weber-Fahr, Global Business Line Leader for IFC’s Sustainable Business Advisory
“Unilever’s Sustainable Living Plan includes a target to halve the environmental footprint of our product portfolio across the life cycle. Water is one of our key metrics and we support efforts to standardise methodology and improve access to scientifically robust and standardised data. The Global Water Footprint Standard is an excellent resource and fundamental to us achieving our targets.”
Dr. Donna Jeffries, Sustainability Manager, Unilever
“Forty years down the road we will have 9 billion humans living on the Earth. Nearly fifty per cent more than what we have today. The impact of any activity, be it economic or social, will have an unprecedented print on water. It is, therefore, critical that policy makers and the public, let alone the political community, are aware of what the water footprint is, how it is established and how it does evolve in time and space. This book is a must for all those who wish to understand why and how water became the single most important commodity humanity has. But most importantly, it also provides methodologies of comparing the footprint of our various actions in order to strive towards sustainable water use.”
Professor A. Szollosi-Nagy, Rector, UNESCO-IHE Institute for Water Education
“The Global Water Footprint Standard comes at a time when companies in all sectors are awakening to the risk that water scarcity poses to their bottom lines and reputations. This work helps companies understand their dependency and impact on water resources, and offers guidance on response strategies that conserve water for industry, communities and nature.”
Jim Leape, Director General of WWF International.
“Clean, fresh water is increasingly scarce world-wide for people and nature. It is therefore essential that businesses or citizens that want to act responsibly understand their water use and its impacts. The standardized methods developed by the Water Footprint Network to analyze and compare water uses are important in this respect. WWF applauds the publication of this guidance through which a valuable tool becomes available for everyone.”
Johan van de Gronden, CEO WWF-Netherlands
“The global water footprint standard developed by the Water Footprint Network is helping C&A to understand its water use throughout its supply chain in countries like India and China. Of interest is the comparison of the water footprint of conventional and organic cotton. The scientific rigour and clarity of the global water footprint standard will help C&A set goals for reducing its impacts to rivers and lakes, adopt corporate policies for reducing our water footprint, and move toward sustainable water use. As a WFN sponsoring partner, we fully endorse the global water footprint standard and the work of the Water Footprint Network.”
Philip Chamberlain, Head Of Sustainable Business Development – C&A Europe
“The Spanish Government issued guidelines to all Basin Agencies to evaluate the water footprint. Evaluations of the water footprint in Spain are helping Basin Agencies get a better idea of water scarcity in Spain and are helping us rethink water and food security.”
Alberto Garrido, Professor of Agricultural Economics of the Technical University of Madrid, and Deputy Director of the Water Observatory of the Botin Foundation.
“We at DEG, member of KfW Bankengruppe, value water as one of the most important natural resources. We actively engage to finance entrepreneurial initiatives in the water sector aimed at creating a sustainable use of water. Congratulations to the second edition of the Water Footprint Assessment Manual, which can help our clients to understand better their water risks and opportunities in a globalizing economy.”
Dr. Peter Thimme, Director Sustainable Development, Environment, First Vice President, DEG
“Water footprint assessments are helpful in supporting our water stewardship efforts because they provide a tool to measure and understand water use throughout our supply chain. Our recent assessments and the report we issued with The Nature Conservancy, with support by the Water Footprint Network, has shed valuable light on the components and locations of water embedded in some of our key products as well as the potential effects on local watersheds. This work provides a foundation for engaging our suppliers and partners as we continue our journey to establish a truly water sustainable business. A common, standard tool for assessing water footprints, as the Water Footprint Network provides, is critical as businesses work toward stewardship of this critical, shared resource”
Greg Koch, Managing Director, Global Water Stewardship, The Coca-Cola Company
“A decade ago, the architects of the water footprint concept captured the world’s interest by unveiling the volumes of water required to produce the goods we consume in our daily lives. Those water footprint numbers made us aware that personal and corporate responsibility for water use extends well beyond the walls of our homes or our factories — it extends throughout the supply chains, particularly the farm fields, where water is consumed in delivering goods and ingredients to us. Now, with the publication of The Water Footprint Assessment Manual, we have come to appreciate the fact that true water stewardship is not solely about the volume of our water footprints – instead, it’s about paying attention to where those footprints land, in local watersheds, and paying attention to the undesirable impacts that come with unsustainable water use. This Manual will be invaluable to anyone wishing to assess, and improve, the sustainability of their water use.”
Brian Richter, Managing Director of Global Freshwater Program, The Nature Conservancy
“In Brazil there is a lot of interest in the water footprint, among scientists like me, but also within environmental organisations, governments and companies. It is very helpful that with the publication of the Water Footprint Assessment Manual we have an international standard, that defines the water footprint unambiguously and that will help practitioners to apply the concept in a way that is scientifically sound and robust. We are looking forward to achieving progress on sustainability, innovation and entrepreneurship.”
Professor Eduardo Mario Mendiondo, University of Sao Paulo, Brazil
“The Alliance for Water Stewardship applauds the Water Footprint Network’s pioneering work and welcomes these further developments of “water footprinting” as a water accounting methodology which will help individuals, businesses and governments move towards sustainable water use worldwide.”
Matthew Wenban-Smith, Alliance for Water Stewardship
“The interest in the water footprint in China is growing rapidly. The global water footprint standard as developed by the Water Footprint Network will be extremely helpful in guiding researchers, companies and governments at all levels. The standard is based on the most recent scientific knowledge and has been extensively tested in a number of pilot studies.”
Professor Junguo Liu, Beijing Forestry University, China
“SABMiller has made extensive use of the Global Water Footprint Standard in its efforts to better understand the water risks across its value chain, make appropriate measures to mitigate these where appropriate and in so doing work towards a more sustainable use of water resources. We value the expertise and rigor that has gone into developing the document, and continue to support the Water Footprint Network in its efforts in this regard.”
David Grant, Group Sustainable Development Projects Manager, SABMiller
“Population growth and economic development is placing enormous pressure on our already scarce fresh water supplies. We produce water thirsty commodities in dry locations, we over allocate water resources within watersheds, and we continue to overwhelm our natural systems with pollution, placing more than 126,000 freshwater dependent species, as well as human beings, at great risk. The Water Footprint Assessment Manual is an extremely valuable tool and standard methodology that we hope will be widely adopted by governments, non-profits, corporations, and watershed managers to ensure the sustainability of producing various goods and services in various locations and to accurately report water use and management information across product supply chains and in watersheds.”
Russ Mittermeier, President, Conservation International
“Water footprint assessments as specified in this document prepared by the Water Footprint Network are an important tool to quantify water volumes throughout the supply chain of products. This is being demonstrated by the increasing number of companies that use this tool. When moving from quantification to communication it is important to contextualize the meaning of the quantified volumes. At the global level this task has been identified as the challenge ahead when moving forward towards widely accepted benchmarks in the area of water stewardship.”
Guido Sonnemann, Programme Officer, UN Environment Programme
“The Water Footprint Network has since its establishment provided a global, multi-stakeholder platform to advance the dialog around the quickly-emerging topic of water footprint. At PepsiCo, we believe that there is significant value in understanding the components of our water footprint from the perspective of local impact. In turn, understanding and addressing this local impact is a critical element in our commitment to respect water as a fundamental human right.”
Dr. Liese Dallbauman, Senior Manager of Water Stewardship, PepsiCo
“This standard clarifies all methodological questions that professionals and water managers may have on the implementation of the water footprint concept.”
Professor Hubert Savenije, Delft University of Technology, The Netherlands
The goal of sustainable water footprints is now more possible – the Global Water Footprint Standard enables consumers, businesses and governments to use and manage water more sustainably and equitably.
The Water Footprint Network and its partners apply the Global Water Footprint Standard in river basins around the world to understand how best to move toward a sustainable water footprint.
For more information please contact:
Ruth Mathews – Executive Director of the Water Footprint Network
Tel: +31 53 489 4370
Email: ruth.mathews@waterfootprint.org
Prof. Arjen Hoekstra – Scientific Director of the Water Footprint Network
Tel: +31 53 489 3880
Email: arjen.hoekstra@waterfootprint.org
Reticulation Reconsidered
Sometimes I write articles promoting on-site water and wastewater services, from a sustainability perspective. For example, this article. As a result I sometimes get emails from water engineers saying things like “there’s no doubt that reticulation was the greatest single contributor to disease reduction”. My response has always been that it wasn’t reticulation that reduced disease; it was the knowledge of how disease was transmitted. Reticulation was just the method used to apply that knowledge, but alternative solutions were and are possible.
More recently I’ve realised that reticulation in fact came out of a degree of ignorance of how disease was transmitted. This can be plainly understood when one studies the history of London’s wastewater in the nineteenth century, where the evidence points to the fact that the cholera epidemics were the result of ill-conceived reticulation.
In the mid-1800s, an estimated 200,000 cesspits were used for disposal of wastewater in London. Chamber pots were emptied into the cesspits, or sometimes composted, but low levels of water use meant that the cesspits often performed adequately. Increasing convenience of water supply in the first half of the century – the introduction of reticulated supplies of ‘potable’ water, followed by the introduction of flushing toilets, led to more water use and thus more wastewater production.
Toilets came into use in wealthy homes initially and then, following the Great Exhibition of 1851 (which featured ‘water closets’ that visitors could ‘spend a penny’ to use), flushing toilets became used for public toilets and more widely in people’s homes. The increasing water use meant that the cesspits used to dispose of wastewater across London became full and because they cost one shilling to empty, they were frequently neglected. The result was effluent running down the street drains, designed for rainwater, but now contaminated with household and industrial wastes, including from slaughterhouses. Disease resulted, with cholera becoming widespread from the 1840s.
In response, the Metropolitan Commission of Sewers ordered all the cesspits closed and required household drains be connected to sewers, which already existed but were used for stormwater only. Unfortunately, the sewers all emptied into the Thames, contributing greatly to the ‘Great Stink’ of 1858, which temporarily closed parliament, and subsequent cholera epidemics. Maps of the epidemics show the downstream parts of London to be more affected.
Dr John Snow famously showed in 1855 that cholera was transmitted by contaminated water, considered to be a founding event in the science of epidemiology, due to the methodology he used. But, at the time, this was ignored. The prevailing theory was that offensive odours, or miasmas, were the cause of disease. The fecal-oral pathway of disease transmission and germ theory were not widely accepted until the end of the century. The great interceptor sewers (built alongside the Thames) were built to mitigate the odours. Completion of the sewers in 1866 abated the odours and coincidentally also reduced the contamination of the Thames, a major source of drinking water, and thus reduced the incidence of disease.
In summary, we can see that knowledge of the cause of disease was not applied in the solution of the time (reticulation of sewers). The sewers worked not because they reduced the odour, as was thought, but because they separated sewage from drinking water. Moreover, the reticulation of water supply preceded the epidemics and contributed to them by overloading the cesspits. Initial attempts at sewering worsened the problems by concentrating the wastewater in the Thames. The solution was to move the wastewater further downstream, into the Thames Estuary. All of this done without understanding of the method of disease transmission and in effect was something of a fluke.
Discussing the matter today, the World Bank has said that Western sewage practices, “. . . do not represent the zenith of scientific achievement, nor are they the product of a logical and rational process. Rather, [they] . . . are the product of . . . A history that started about 100 years ago when little was known about the fundamental physics and chemistry of the subject and when practically no applicable microbiology had been discovered. These practices are not especially clever, not logical, nor completely effective – and it is not necessarily what would be done today if these same countries had the chance to start again.”
Had modern on-site and community wastewater systems (or even composting toilets and better cesspit management) been employed as the response to increasing water use, then much of the cholera epidemic could have been avoided. Indeed, had people simply understood the transmission of cholera, conditions could have been much improved. On-site rainwater capture would have been a better option too than having water piped from the contaminated Thames, for example from the Southwark and Vauxhall Waterworks Company, whose water accounted for 286 deaths in a cholera outbreak in 1854 (as established by John Snow). There were a range of potential solutions to separating people from their faeces and in particular in the sourcing of drinking water from uncontaminated sources. Reticulation as a particular solution was eventually effective, but created environmental problems downstream and huge ongoing expense to maintain and upgrade the systems.
However, perfect performance is not possible, no matter how much is spent: every year the Auckland region sees 2.8 billion litres of sewer water overflow into its streams and harbours (based on the last published figures, in the 2007 Auckland Water Industry Annual Performance Review). That is about four times the volume of oil leaked into the Gulf of Mexico as a result of the Deepwater Horizon explosion.
Water footprint video (your water footprint = the stuff you buy)
Visit the Post Carbon Institute and watch their video about water footprints. Why are they so important and how can we reduce them?
Click here.
Water map shows billions at risk of ‘water insecurity’
From Richard Black on BBC News, Science & Environment:
About 80% of the world’s population lives in areas where the fresh water supply is not secure, according to a new global analysis.
Researchers compiled a composite index of “water threats” that includes issues such as scarcity and pollution.
The most severe threat category encompasses 3.4 billion people.
Writing in the journal Nature, they say that in western countries, conserving water for people through reservoirs and dams works for people, but not nature.
They urge developing countries not to follow the same path.
Instead, they say governments should to invest in water management strategies that combine infrastructure with “natural” options such as safeguarding watersheds, wetlands and flood plains.
Volumetric water charging recommended by Land and Water Forum
The Land and Water Forum report “A fresh start for fresh water” includes the following recommendation (p55):
A new charging system: Efficiency and environmental gains will result from requiring water utilities to meter and charge users for their services on a volume-related basis. Developing definitions of reasonable domestic take and setting up national templates for demand management plans should be part of this system. The gains possible from this include:
- more efficient use of water, as a price signal for supply is added to the range of other measures that can be used to encourage water efficiency. Those councils that apply a volumetric charge to water tend to have much lower water use than councils that do not
- more efficient use of water means that there will be meaningful deferrals to the need for future infrastructure and its development cost
- the experience in Auckland is that there are considerable energy savings possible as less water (and wastewater) needs to be pumped.
Click to download the report “Land and Water Forum (2010) Report of the Land and Water Forum: A Fresh Start for Fresh Water” from the Land and Water Forum website.
DR3500.5 – death by consultation to greywater and rainwater systems
The draft standard 3500.5 has been released for comment. In the current format this would effectively prohibit greywater recycling and rainwater reuse in New Zealand. Why? Because it contains onerous requirements to consult with multiple parties before installing greywater recycling systems or rain tanks. This could be expected to proceed smoothly in Australia where the relevant public bodies have published policy and understanding, or at least awareness of the issues. But in New Zealand, prior experience of consultation around these matters (by myself and others) leads me to believe that, in the absence of any extended debate and policy-making on these issues, the consultation process will become a massive barrier to sustainability, resulting in a time-consuming process that few are equipped to undertake, with the outcome almost certainly being ‘no’, or at best ‘yes – if you do a whole bunch on illogical, expensive and counter-productive things’.
This is my submission, which you are invited to cut-and-paste (and edit) to help form your own submission:
Comment on clause 12.3.5
It is proposed in the standard that consultation should be undertaken with five different parties for every single greywater system installation. This is inefficient, but I can see why it could make sense in Australia where policy differs between states. Further, in Australia those parties will have the prior knowledge and experience and written policy to refer to, meaning that consultation should be relatively straightforward. In New Zealand, my experience of consultation on greywater systems and other on-site systems (rainwater, wastewater) is that most of these bodies do not have formulated or documented policy and most individuals in them do not know how to, and would not want to, undertake consultation on this topic. Thus they would tend to either oppose any proposal as a default, or to defer (pass the buck) to the other organisations listed (or still other organisations unlisted) or agree, but only with unreasonable conditions. Either way, the result is a tremendous barrier to sustainability. I would add that there aren’t many people in New Zealand that would agree to undertake such a consultation process (whether homeowners or engineers, etc.) given the time delays and hassles and their own lack of knowledge to negotiate the various organisations, or if they did, they would be readily put off at the first hint of bureaucracy. The net result of requiring this consultation for every greywater system is that almost no greywater systems will ever be installed in New Zealand, which I assume is not the intention.
Note that if an organisation holds an unreasonably obstructive view, this is given great power of veto by the proposed clause, yet the view is not open to scrutiny as it is not itself published and subject to public comment. Deferring policy decisions to (possibly untrained and unwilling individuals within) these organisations is not a reasonable, nor a transparent process. It is certainly open to abuse (asking a network utility operator if they should lose income, for instance) but more likely it will fail due to lack of interest. It certainly will not work in New Zealand at present.
E.g. it recently took me eleven months to gain consent for an on-site wastewater system in Auckland, with only the local council and water supplier being consulted. If other parties had also been involved it probably would not have been possible to negotiate the bureaucracy.
This provision is simply unnecessary in any case because the building consent process is sufficient and appropriate. I note that a building consent is required for such systems. Councils should already be consulting with these organisations as they form policy on greywater recycling (which indeed they have done in instances of policy formation of which I’m aware). There should thus be a council policy which incorporates the views of the other organisations. When policy changes, consultation happens again. Consent applications simply need to show how they meet the policy requirements and council simply needs to process the application against the policy. If it diverges from policy then council may seek further consultation, but this should not be left up to the applicant as there is such imbalance of power and the process itself therefore becomes a deterrent to the use of these systems – rather council should take the leading role in consultation.
Proposed change to clause 12.3.5
The preferred change is simply that the requirement to consult is removed.
As a less-preferred alternative it should be stated that it doesn’t apply to New Zealand.
As a still-less-preferred alternative it should be stated that consultation with these bodies is the responsibility of local councils during policy formation and/or consent processing, not a requirement that individuals must undertake for every single application.
Comment on clause 6.2.1
This clause states that consultation on rainwater systems is required with the health authority and water supplier (network utility operator), for every single installation. Neither body has been very progressive in New Zealand in terms of sustainable water systems and have stymied attempts to more widely introduce on-site rainwater systems. The health authorities do not have confidence in anything but centralised systems because they don’t make standards for smaller systems (they are being asked to pass something out of their control) and the water supplier is simply protecting a business position. It’s not right that every individual wanting to install a rainwater system should have to deal with these organisations; it’s a massive power imbalance of the sort which should not be designed into standards. Rather, the local council should undertake to develop best practise policy and should do so in consultation with them. Although councils often have to struggle against these organisations to get sustainable policies implemented, at least the power imbalance is less and at least the process occurs within a defined period and once policy is formed the consultation needn’t proceed indefinitely for every single installation.
Proposed change to clause 6.2.1
The requirement to consult with the health authority and water supplier over every single installation should be removed from the standard. Instead it could be noted that councils should process the application in accordance with policies they have developed in consultation with the health authority and water suppliers, although this is simply stating the current situation.
Comment on clause 2.19.3
It appears that excessive backflow prevention measures are required in some situations. For example the requirement for a device at the property boundary appears to apply irrespective of whether the greywater system is completely separate from the potable water system. Why would this be necessary if, for example, the greywater system supplies only the toilet cisterns and/or a self-contained irrigation system? The risks of cross-connection (presumably the only motivation for requiring the site to have backflow prevention at the boundary) are adequately mitigated for single domestic dwellings by the building consent and inspection process and the use of appropriately coloured and labelled pipe. The rules to prevent cross-connections where potable water is used to top up greywater tanks are extant and sufficient. Whilst large-scale reticulated recycling systems (third pipe systems) clearly do pose cross-connection risks (which have not been adequately addressed, given that they continue to occur) I’m not aware of any cross-connection incidents for an on-site system. Finally I note that the hazard ratings state “any condition, device or practise that, IN CONNECTION WITH THE DRINKING WATER SYSTEM [etc.]”. If a greywater system is not connected to the drinking water system (and not able to be without modifications to the plumbing) then this must be excluded from the need to have general backflow prevention for the site.
The use of hose connection vacuum breakers is reasonable and in fact should probably be mandatory for all external taps whether or not greywater systems are used.
Proposed changes to clause 2.19.3
Any greywater system which is not connected to the drinking water system (is self-contained in its supply to toilets and irrigation systems, for example) should not require backflow prevention to be installed at the boundary.
Comment on clause 2.20
Is an air gap not effective unless it is registered?
I understand that an air gap could POSSIBLY be removed or modified by somebody, but that would breach the building consent, which is deemed an adequate control for most other building systems. Is it likely that somebody would illegally remove or modify and an air gap? Assuming that it isn’t, it is therefore hard to justify annual inspections on small-scale systems – there’s no requirement to register and check the rest of a legally-installed plumbing system on a regular basis, so why should this be different? If illegal modification doesn’t occur then the system will be safe. I note that a toilet cistern is sometimes used by greywater systems to achieve an air gap and would have thought that this is most unlikely to be compromised.
Proposed changes to clause 2.20
Preferred option: allow unregistered air gaps for single domestic dwellings for greywater and rainwater systems (so long as they are designed according to standards and installed in accordance with a building consent).
Less-preferred option: allow greywater and/or rainwater to be plumbed direct from the storage tank to toilet cisterns and regard these as exempt from the requirement for registration and testing as air gaps.
ENDS
Link to draft standard
Link to submission page
August 31, 2011 at 5:02 pm Leave a comment