Leakage problems demand comprehensive solutions, not only "quick fix" repairs

By Mike Setford, Richard Pilcher

World leaders once shied away from problems hidden in decrepit water pipes beneath their cities, towns and villages. Commentators watched in despair as the water industry in many countries limped along "Cinderella style" — politicians cutting red tape on multi-million pound (£) sterling new plants while scant resources were spent on crumbling underground infrastructure. All of that is changing as an increasing emphasis on leakage is emerging internationally, and water professionals are calling for a new comprehensive solution.

In August 2002, Nelson Mandela addressed the World Summit on Sustainable Development in Johannesburg, South Africa, about the importance of water, and made world leaders focus on this serious problem. He urged the attending government ministers and delegates at the global event to make access to clean water a basic human right. Suddenly the fact that some 30 to 70 per cent of the world's treated water supplies are lost through leaks took on new urgency.

Some 1.2 billion people lack adequate clean drinking water, according to the World Health Organization, and millions die annually from waterborne diseases due to inadequate sanitation. For years, droughts have blighted efforts to develop agricultural and tourist industries, yet some water experts maintain that protecting this precious resource - water - could be made much easier by reviewing and then improving leak management worldwide.

A leak noise correlator is used to pinpoint the source of a leak

The World Bank and European Investment Bank are investing in leak reduction and the International Water Association (IWA) highlighted the issue at an international conference on leak management, held in Cyprus last November 2002. Water professionals from 27 countries attended.

National leaders in relatively wealthy countries, including in the Middle East, are examining leakage rates before deciding to build desalination plants in order to increase water supply. The impetus for change is growing, egged on by increasing evidence of the social and economic price being paid worldwide for failing to reduce leakage to "economic levels." The economic level of non-revenue water (NRW) is defined as having been reached when it would cost more to reduce NRW by one metre square volume than the value that can be attributed to that metre square volume of water.

"It is no longer acceptable to regard the problems of meeting water demand purely in terms of identifying additional new resources of supply without first reducing existing water losses from distribution systems," according to Thas Athanasiou, managing director of Halcrow Water Services. "Reducing such losses often has a far shorter payback period, particularly in arid and semi-arid countries such as Cyprus, where water is precious," he added.

In the UK, most water companies have achieved an economic level of leakage with the latest figures showing that leakage rates have decreased. Before privatisation and independently audited regulation of the water industry, it was commonplace for 30% to 40% of the treated water entering the distribution system to be lost due to leakage. The best performing companies report leakage rates less than 20% now. Canada, Germany and Malta provide other examples of significant reduction of leakage and non-revenue water, although the majority of countries in the world are playing "catch-up."

The UK consultancy Halcrow Water Services has helped water companies in several countries to reduce leakage and NRW, including Venezuela, where significant savings were achieved. The financial payback period on this type of project typically ranges between two and five years, but even shorter periods are possible.

Mike Setford, the head of operations for HWS, explained: "Many countries are now waking up to the fact that the loss of 30% to 70% of water in the system represents a huge cost to that organisation on an annual basis. Whatever condition their infrastructure is in, it is only going to get worse through neglect. There isn't a quick fix solution. If nothing has been done to a system it can take several years to get leakage levels under control. Once it's reduced to an acceptable level, it's equally important to maintain it at that level."

Many countries have drafted in the necessary manpower to fix leaks, but some have concentrated their efforts primarily on replacing pipes, which is only part of the solution. Malaysia, for example, has invested in major pipeline replacement projects, but could benefit more by taking a wider approach. Pipe replacement is only part of the solution; a programme of leak detection, repair and water pressure reductions must also be undertaken.

One of the primary reasons for pipe bursts is high water pressure. Bursts are more common when pressure levels exceed 50 metres head (72.5 psi), so managing water pressure in the network is critical to reducing leakage. For example, one Mediterranean town loses nearly half of the water that goes into the distribution system. The main reservoir is 90 to 100 metres above sea level, the old town is 50 to 60 metres above sea level and the new area under development is only about ten metres above sea level. Strategically located pressure reducing valves in the distribution system could significantly reduce leakage levels overnight and leak repair costs for the operator.

Leakage is also caused by a combination of factors, including the age of the pipes, manufacturing processes, aggressive soil, traffic vibration and climate. The shelf life of pipes can vary from six to 150 years. In Malaysia, some recently laid pipes became brittle due to contaminated resin used in the pipe manufacturing process. Some types of clay can corrode iron pipes in less than a decade, while the same pipes could last for more than a century in chalk. Modern practices favour polyethylene pipes, but due to its relatively recent introduction, data is limited on their long-term durability. Polyethylene pipes, however, are generally expected to be durable for many years.

Poor management of leakage can lead to water rationing with the local population living from one day to the next without knowing when the tap will be turned on. This situation can affect human health. For example, when water supplies are intermittent, depressurisation can siphon surrounding contaminants, such as sewage, through holes in the pipes. The distribution system should, therefore, be kept pressurised at all times so that outside water cannot seep into the treated water supply system.

Cross-section of a pipe heavily corroded internally before and after it is coated with epoxy lining, which extends the life of the pipe and increases water flow.

Less water rationing is also better for economic reasons. For example, the reduction of water leakage can save significant amounts of money in Cyprus, which relies heavily on the more expensive water treatment process of desalination. Every cubic metre of water saved is worth about US$ 0.60. This figure is significantly higher in other parts of the world.

Comprehensive approach

Halcrow Water Services uses the latest techniques and methods to reduce leakage and future planning to ensure leakage is maintained at a low level. The first step in managing leakage is the technical audit; HWS staff visits clients and with their cooperation calculate losses using an IWA standard water balance approach. Once the extent of the leakage is known, then it is possible to work on the best solution. The company will send in small specialist teams of consultants to work in partnership with communities, which lack the equipment and expertise to resolve their problems.

Typically, the problem will be tackled in a number of ways. Pipe replacement is the most expensive form of leakage control, while the repair of only the worst leaking pipes is the least expensive.

Many other services are involved and leak detection methods have changed radically over the last 25 years. A major breakthrough occurred in about 1980 when a British invention, the first leak noise correlator, came onto the market. The technology has been updated ever since with the seventh generation digital correlator being produced in 2001. Currently correlators can accurately pinpoint the position of the leak to within half a metre. This technology marks a giant step forward from the days when leakage inspectors used a steel rod with a wooden earpiece (listening stick) to try and pinpoint leaks. These devices are still a very important "tool in the armoury" of the leakage inspection team. In busy towns and cities leak teams still work at night when extraneous noise is lower and leaks can then be identified more easily.

Part of the modern day approach to unacceptably high losses and wastage from the water system involves evaluating water supply and usage by dividing it into different components and then using this information in conjunction with specialist software to help evaluate the best solution. This approach includes the reduction of physical losses, undertaking meter reviews (apparent losses) and also pipework replacement programmes.

Until recently, the practice of controlling leakage from water supply and distribution networks could have been considered more an art than a science. A set of concepts known as Bursts and Background Estimates (BABE) are now applied as component-based computer models in many places around the world.

Leakage control consultants are now equipped with tools for making a fully integrated assessment of all technical and economic components of leakage control. These concepts are used to assist in strategic assessments, day-to-day leakage management, planning and design.