What is the Water Loss Task Force?

The International Water Association (IWA) is a global network of water professionals spanning the continuum between research and practice covering all facets of the water cycle with approximately 10,000 individual members in over 120 countries throughout the world.  The Specialist Groups represent the core vehicle for issue-based interaction on scientific, technical and management topics; they facilitate collaboration and product generation including conferences and publications.  The Specialist Group Efficient Operation and Management of Urban Water Systems (EOM SG) is the forum for discussing, promoting and seeking opportunities for improvement in water supply systems through efficient and sustainable strategies and practices.
 
The Water Loss Task Force (WLTF) is one of the several Task Forces of the EOM SG. The WLTF vision is to provide leadership in the field of water loss management through effective and sustainable international best practices. Water loss management is of fundamental importance in the application of efficient and effective strategies for reducing water losses from distribution networks.

The WLTF now boasts around 200 members in 35 countries. Many of them work in designated teams towards specific goals, targeting different angles with the aim to improve the resources available to water utilities to minimise their water losses.  The recent Water Loss 2007 conference in Bucharest saw record participation, with 110 abstracts reviewed, 93 oral and 12 poster presentations given.  This was one of a series of events held in the run up to the 6th World Water Congress, to be held in Vienna in September 2008.
In recent years the WLTF has made several significant steps towards its goal. The ‘Water Balance and Performance Indicators’ methodology that came from them, used for the quantitative monitoring of water use and water loss in drinking water systems, has already been adopted as the basis for many global water utilities.  Members of the task force have also assisted the World Bank Institute in producing a series of training manuals designed for use in developing nations, where making the most of scarce existing water resources can be especially valuable.

Currently the main initiatives being worked on are the: ‘Acoustic Noise Principles and Applications Initiative’, ‘Repair of Replace Dilemma for Services and Mains Initiative’, ‘Apparent Losses Principles and Applications Initiative’, ‘Training on Water Loss Management Initiative’, and ‘Target Setting and Strategy for Water Loss Management Initiative’.  By examining these areas and researching current standards and thinking across the worldwide water industry, the WLTF hopes to provide objective and qualitative information on best-practice methodologies from which everyone can benefit.

The WLTF was also responsible for evolving the four essential methods of managing real losses of water: pressure management, decreased response time for fixing leaks, active leakage control, and improving infrastructure conditions.  Each and all of these approaches can have a significant effect on the volume of water lost due to leakage, both individually and in combination with each other.

 

Why is Water Loss Important?

470 million people currently live in regions where severe water shortages exist, and by 2025 this is projected to have increased by a factor of six.  This would mean that 3 billion people will be living in water-stressed countries.  Even now, 2.6 billion people lack basic sanitation facilities and over 1 billion drink water from unsafe sources.  Large cities in developing countries find that the water supply is hampered by approximately 40% of their System Input Water being Non-Revenue, and the average person there uses only 10 litres of water per day – in the UK, that average is 135 litres/day.  Even in the US, a survey from 2005 predicted that 35% of the nation’s cities would face critical water shortages within 10-20 years.  At the rate water is already being used, not to mention the rate at which the need for it is increasing, any clean, safe water must be treated – as it should be – as a valuable and valued natural resource.  [Statistics from the IWA]

The USGS estimated in 1995 that approximately six billion gallons of water were lost each day in the US out of 40 billion supplied.  All too often this is either ignored or accepted as an unavoidable loss.  Water that is supplied to a system but fails to reach the end user is pure waste; it is a stealth tax unasked-for and unnecessary to pay, collected by no one and to no benefit for anyone.  [Statistics from USGS, Estimated Use of Water in the United States in 1995]

It has been repeatedly proven that the correct implementation of leak detection and location technology is not only of great benefit environmentally, but also from a purely economic viewpoint.  Finally it is worth noting that, irrespective of the amount of water being lost through the distribution network, the necessary volume of water to be supplied requires to be increased by the same amount; this then increases the amount of water needed to be processed and purified, once again increasing the costs and environmental impact of the loss.
What to Do About It

Although the actual physical leak repair and maintenance of pipe infrastructure are two important factors in water loss reduction, we will focus here on pressure control and leak detection, as these are arguably easier to improve effectively and have greater immediate impacts on efficiency of water supply.

The turnaround time between a leak occurring, its detection, location and repair is crucial to reducing losses.  More time equals more water lost, with a direct, linear relationship – although an unattended leak has the potential to get worse, which then could turn it into an exponential equation. 

Pressure management is important for several key reasons: with higher pressure, more water is lost per time period through a leak or break of any given size.  Higher pressure also leads to a higher frequency of break and leaks, as the pipes and fittings are being put under greater stress.  Calculating the optimum system pressure for any given time is relatively easy once flow and pressure data have been gathered, however the problem has been in physically adjusting it to the optimum level.  The good news is that equipment are available to help: pressure reducing valves and PRV controllers can be fitted to limit the pressure of water supplied to a zone at different times according to a pre-programmed plan.  Some PRV controllers even allow remote programming for optimisation control, making the operation even easier.  This also allows for the potential to have an automated system which utilises remotely-gathered flow – and even noise-based leak – data to program the unit on the fly, which would make the basic infrastructure optimise its own efficiency at any given time.

Leak detection follows the principle of LLP – Locate, Localise, Pinpoint.  The installation of dataloggers at points throughout the water network, dividing it up into DMAs, and then analysis of the night flow through each area relative to total water flow at supply, is the established method of detecting and locating ‘unreported’ leaks.  DMAs with unexpectedly low flow rates are then targeted by leak localisation teams, who will carry out acoustic surveys of the area.  Noise loggers, which listen out for and record possible sounds of leakage, are affixed to the pipes at set intervals.  These can be permanent or temporary deployments, as they are typically attached externally by magnet so installation is usually quick and easily reversible.  Leak detection teams would then patrol the area, picking up readings from each logger in order to find the local area of the leak.

Technological advances have been made which make this process quicker: first, with certain noise loggers, came local wireless transmission capability – leak detection teams could simply drive or walk past in the vicinity of a logger, and have the data transmitted to a PDA or similar handheld device. 

The next step is already approaching rapidly: sophisticated noiseloggers with long range transmitters installed in a permanent network, to automatically record and collate noise logging data and send it straight to a remote location – typically a personal computer.  This creates an active system that is always listening out for any leak within its perimeter; it can be set to send the acoustic data both on a regular basis (i.e. daily), and also immediately when it detects that certain programmed parameters have been met which would indicate a leak.  With immediate detection and location of leaks, time is saved and resources are freed up to repair the leak with maximum expediency.

Once a leak has been located, it needs to be localised.  To do this, leak noise correlators are employed.  These typically use 2-3 listening outstations positioned along the pipe in question, and a centralised device to correlate the data gathered to quickly provide a precise location from only one deployment.  This method is constantly being improved by technological advances, and now there are even effective digital correlator systems which make the process even easier.  In the past, correlation was highly dependant upon the quality and veracity of information provided to the system – and in many cases the essential variables could be unknown.  Wireless connectivity, the integration of presets for pipe- and flow-specific details, the use of a 3-outstation system for subjective velocity checks, and automated digital data processing and graphing all reduce the onus on the operator and provide the capability for even faster and more accurate leak localisation (even bordering on pinpointing).

Finally, the leak needs to be confirmed and/or pinpointed, and this is still largely done with the use of listening sticks – albeit electronic ones now.  Noise amplification, automatic or manual filtering, minimum noise level profiling and visual analytical displays all speed up and ease the process from the days of literally putting one’s ear to the ground.  These latest developments always work to reduce the overall turnaround time, make the job easier, and improve efficiency by decreasing the incidence of costly ‘dry holes’.

 

Conclusion

Simply throwing resources at issues such as pressure management and active leak control is one way of improving those aspects of water loss management, however such a brute force effort is always going to be limited in its scope for effectiveness, and even more limited in its efficiency.  Gathering information is the first step in identifying how any problems can be best resolved, before the best approach to tackle them can be chosen.  Training and information sharing at all levels of service is essential to achieving success, and personal experience is still invaluable to a leakage engineer, but the use of up-to-date technology and methodology can ease the entire process.  When time and resources have gone into building an effective system – any system – those investments are saved many times over when the system is implemented.  This is particularly evident in largely automated (typically computerised) systems, where the burden of processing is placed with devices specially designed to do them.  By separating and specialising responsibilities not just between people but also by sharing them with technological systems, each aspect becomes more efficient – and the whole benefits greatly as a result.
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This article was prepared with the aid of information from several sources, including Bambos Charalambous (Chair WLTF, bambos@wbl.com.cy), Stuart Hamilton (Secretary WLTF, shamilton@hydrotec.ltd.uk), and David Field (Member WLTF, Sales Manager Halma Water Management, dfield@).

Further information about the IWA and WLTF can be found on the following websites: www.iwahq.org and www.iwaom.org/wltf.