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The performance of a clothes washing machine is not directly measured by the volume of water it uses – rather does it provide the intended service? In other words, will the clothes washing machine clean your clothes?  With a service orientated approach, the volume of water becomes a secondary consideration and an opportunity for efficiency where the service can be maintained or enhanced - even delivered through an alternative means that does not require water. 

Separating the provision of a service from the current technology that delivers the service enables new, more efficient approaches to be explored. 

The challenge for the urban development industry is to plan for the water requirements of a development site in consideration of both the technical efficiency of appliances as well as the water use behaviours of the households and businesses that will move into the area. 

Other factors have an influence on water system design within a development site – such as fire flows.  The focus of this fact sheet is to provide an overview of the assessment of water consumption requirements for a development site.  The figure on the right demonstrates the importance of integrating demand management from the planning and design stage, as most of the achievable water savings are realised through decisions made by planners and builders in providing the infrastructure and technology. 

Figure: Magnitude of water savings through the decision cycle
Source: In PMSEIC, 2007 (Based on analysis by Marsden Jacob Associates)

Drivers for water demand

At the scale of the household, there are a number of important factors that influence water demand.  Some of the key demand drivers are:

1. Climate – climate variability and climate change scenarios are predicting a drying climate for much of Australia.  One implication of this trend is expected to be increased water demand – particularly associated with outdoor water use.
2. Design trends (e.g. number of bathrooms) – trends in residential design can have negative impacts on water efficiency.  For example, the preference for en-suites and additional bathrooms can increase per person water use (Troy et al., 2005).
3. Preference for irrigation systems – within society, there is a drive towards systems to assist in managing and maintaining the amenity of the home and landscape.  Automated irrigation systems have the potential to be highly water in-efficient if incorrectly installed or operated.  The percentage of households with irrigation systems has been steadily increasing in recent years. 
4. Affluence – this issue is partly linked to the two points mentioned above.  As householder’s disposable income increases, the opportunity to improve their property (through renovation or re-landscaping for example) will often be associated with an increase in water using appliances and fixtures in the home.
5. Lot size – the trend towards smaller sized blocks has the potential to reduce per capita demand as the outdoor area of lawn and/or garden is reduced.  To date, a significant reduction in water due to these issues tends to be off-set by additional appliances and fixtures. 

Many of these drivers can be considered to have a long cycle and the impact on water demand may potentially be mitigated.  For example, smart technologies applied to outdoor irrigation systems can dramatically improve the efficiency of water use without compromising the plants and the amenity of the garden. 

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Appliances and fixtures

Within the home, water use is primarily associated with specific fixtures and appliances.  From dishwashers and clothes washers to baths, spas and pools, there are a significant number of appliances and fixtures found in homes today.  In categorising water use associated with these appliances and fixtures, a simple distinction can be made between event based and duration based water use.   

Planning and designing for residential water use requirements - or end use of water - requires an understanding of both the performance of the technology and the behaviour of the householder.  These issues are explored in the following sections of this fact sheet. 

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WELS Star Rating

WELS is Australia’s water efficiency labelling scheme.  The scheme requires that certain products be registered and labelled with their water consumption based on the national standards.  The scheme is now mandatory for showers, taps, toilets, urinals, clothes washers and dishwashers to be registered and labelled. 

More information, including a database of WELS registered products, can be found at http://www.waterrating.gov.au/about/
 

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Minimum performance standards

At the national level, minimum performance standards are considered as an extension to WELS.  Currently minimum performance standards only apply to toilets.  It is a requirement for all toilets to have an average flush volume of 5.5 litres or less. 
While no other appliances or fixtures are currently subject to minimum performance standards, extension of this approach to appliances such as clothes washers is being explored.  In 2006 the Environment Protection and Heritage Council Ministers agreed to a long-term programme of work on the possible introduction of minimum performance standards for existing Water Efficiency Labelling and Standards (WELS) Scheme products, and on the inclusion of new products into WELS.

See: Ministers report

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Role of water metering

One of the key issues with both planning for, and managing residential water demand is access to meter data on water consumption patterns.  In some of the major cities in Australia, residential water meters are read every three months.  In other cities, the meter read frequency is less – every six months for example. Several studies have explored smart meters, or more frequent meter reading cycles, to gather data on water use at the level of end uses of water.  These studies provide particular insight to characteristics of water use behaviour – frequency and duration of events primarily. 

An issue with most traditional water meters is that they do not measure low flows.  Therefore, leakage within the house or even very low flow applications cannot be detected by traditional water meters.  Arregui et al. (2006) demonstrated at flow rates of less 22 litres/hour a Class B water meter did not register flow. 

While water use data has typically been used by water utilities to support planning, there is an increasing awareness of the use of water metering technologies to provide feedback to the householders on water consumption patterns.  Such technology has been trialled as an incentive to use water more efficiently – instantaneous or near-instantaneous feedback to the householders on water consumption can help improve water efficiency in the home through changed behaviours (Marvin et al., 1999).

Increasing the frequency and detail of water consumption data available to both householders and water planners will provide a range of innovative approaches to residential water management. 

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Managing system losses

Within traditional water systems and networks, there is a significant water loss issue resulting from aging water delivery infrastructure.  In managing this problem, a threshold has been established to indicate an economically sound level of expenditure in addressing water loss – described as the Economic Level of Leakage (Lambert and Hirner, 2000). 

The approach adopted in terms of water system pipe technologies will determine what an appropriate estimation of system losses would be for a development site. 

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Case Study – Aurora

Aurora is a Greenfield development on Melbourne’s urban fringe that has been developed according to sustainability principles.   The development has taken an integrated approach to the delivery of water services that incorporates demand management, source control of stormwater, rainwater tanks for each allotment, and a on-site wastewater treatment plant that will provide recycled water via a dual water reticulation system. Aurora aims to reduce imported drinking water to the site by 70% relative to a conventional development (McLean, 2004).

In designing the water system for Aurora the typical household consumption had to be estimated.  Two factors at Aurora are expected to decrease average household water consumptions when compared to a conventional development.

• Aurora has higher than average housing density, which reduces the area of land requiring irrigation.
• An expected higher uptake of water efficient appliances and fittings in dwellings.   

Read more in the case study for Aurora.

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Implications for on-site water reuse and use of alternative water sources

There are considerable opportunities for use and re-use of water on-site through alternative water sources. The challenge in planning for the use of these new water sources is to ensure that they are adequately sized.  This question of sizing applies equally to the input side of the equation as well as the output side of the equation.  For example, the effectiveness and usefulness of a greywater system that uses water from the shower for garden use will in part be determined by the type of showerhead and the number of people in the house – and in part by the size of the garden, the climate and the type of plants in that garden. 

In this way, projections of water use are central to the design and selection of water service configurations for residential properties. 

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Implications for water restrictions

For cities with rain-fed storages, water restrictions are an integral part of the operation of urban water systems.  The definition of yield from a rain-fed storage includes a set of assumptions about the severity and frequency of water restrictions and savings generated by these measures.  As such, water restrictions have been considered an emergency response measure for times of drought.  Whereas measures such more efficient appliances for example have been considered long term demand management options. 

The key distinction here is the timeframe and the degree of ‘lock-in’.  Measures such as more efficient appliances – driven through initiatives such as WELS or minimum performance standards are considered to be essentially permanent. 

One of the implications that urban water managers are facing is that the assumptions on water savings from periods of restrictions that form a central component to water system yield estimates are becoming less and less valid.  The concept of ‘demand hardening’ is used to describe the reduction in water savings delivered by a specific level of water restrictions due to an increase in the efficiency of water use by the community in the years since the last significant drought.  If, with demand management programs and an increase in the efficiency of day-to-day water use, the estimates of savings from water restrictions are no longer valid, then it is anticipated that yield calculations for rain-fed storages will need to re-visited. 
 

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Future directions for water using technologies in the home

Today’s water using appliances and fixtures will continue to be commonplace in Australian homes for some time to come.  However technologies continue to develop and in many instances there has been a clear trend towards more efficient appliances in recent years.  Equally there are examples of where a new water using appliance has been developed that has rapidly become mainstream and resulted in an increase in per capita water demand (automated irrigation systems are an example). 

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References for water demand data and consumption patterns

There are many different studies and reports on water demand data and consumption patterns that are of value to the development industry.  One of the key distinctions is whether the data has been collected using a top-down or bottom-up approach.  This distinction is based in part of the type of metering approaches commonly in use today. 

1. Top Down – this refers to data collected at the household meter level (by water utilities primarily) for all properties.  This data is typically aggregated to represent particular sub-sectors (such as single residential dwellings) and with the current meter read frequencies being at best quarterly, these data sets provide a picture of average demand.  Demand drivers such as occupancy ratios, level of water efficient appliances in the home and affluence cannot be easily explored and translated to planning data for a new urban area.  This issue is particularly apparent when considering multi-unit properties where there is often a common meter servicing several units. 
2. Bottom Up – this refers to data collected from within the home that provides detail on the type and number of appliances in the home, the occupancy ratios and the frequency of use of appliances and fixtures (water use behaviour) for example.  These data sets are considerably more difficult to collect simply from the perspective of the time involved even with smart meters and specialist survey techniques. 

The following two reports provide examples of resources for estimating household consumption patterns. 

Perth (WA) Domestic Water Use Study

Yarra Valley Water 2004 Residential End Use Measurement Study (Melbourne, Vic)

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Key Issues

Benefits

Benefits of implementing a demand management strategy include:

• Reduced demand for imported drinking water.
• The  volume of wastewater discharged from development will also be reduced.
• Flow reduction will reduce the size of piping required for water and wastewater systems.
• Reduced energy demand and associated greenhouse gas emissions.  This is particularly the case for demand management strategies that target end uses that require water heating.
• Minimise environmental impact of development through reduced demand for water sourced from natural catchments and reduced discharge of treated wastewater to receiving waters.

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Development phase actions

Feasibility

• Consider demographic and occupancy ratios for the development site.
• Linkages with energy demand requirements – the choice of water using appliances and fixtures will have an impact on energy requirements for homes and business – and vice versa.  

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Planning

• Define extent to which plantings in public and private greenspace will be managed and controlled.
• Ensure that planning for use of alternative water sources, as well as water and wastewater system design, considers the anticipated water demand that has been developed at end use level.

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Design

• Consider smart metering technologies and synergies between collection of water, energy and other utility consumption data.
• Decisions around the selection of the water system technologies (in terms of water and wastewater) pipe infrastructure adopted for the development site need to consider the demand projections for both potable water as well as estimates of wastewater generation. 

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Construction

• Select best practice water efficient appliances and fixtures.

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Completion

• Adopt best practice water efficiency measures for businesses and the non-residential sector.

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Arregui, FJ, Cabrera, E**, Cobacho, R and García-Serra, J,  2006 'Reducing Apparent Losses Caused By Meters Inaccuracies', Water Practice and Technology, Vol. 1 (4), IWA Publishing Online.

Lambert, A. and Hirner, W, 2000 Losses from Water Supply Systems: Standard Terminology and Recommended Performance Measures, International Water Association. 

Marvin, S., Chappells, H. and Guy, S. 1999, 'Pathways of smart metering development: shaping environmental innovation', Computers, Environment and Urban Systems, vol. 23 pp. 109 -126. 

PMSEIC 2007, Water for Our Cities: building resilience in a climate of uncertainty, a report prepared by the working group of the Prime Minster’s Science, Engineering and Innovation Council.  

Troy, P, Holloway, D and Randolph, B 2005, Water use and the built environment: patterns of water consumption in Sydney, City Futures Research Centre – University of New South Wales, Research paper No. 1.