Holding back the water

By considering how consumption patterns will change and the potential strain the network will be under, the diameter of pipes can be matched to future demand at the layout and design phase. Through optimising the project at this stage, it will be possible to achieve the longest potential lifespan for the network and maximum flow to end-users.

Adequate maintenance is fundamental to increasing the longevity of a network and to providing a reliable water supply, so a maintenance strategy needs to be thought through early on in the planning phase in order for key elements to be worked into the design, such as creating suitable access, building in sufficient hydrants and dividing the network into zones for flow monitoring.

Perfect pipes

Until about 25 years ago, poor pipe selection was at the root of many pipeline failures, but engineers are now much wiser about the cost implications of bad planning. Furthermore, advances in technology have expanded the range of useable and durable materials available, such as polyvinyl chloride and polyethylene.

Nevertheless, the choice of pipe still influences the performance of a system, its ability to cope with increased demand and the amount of maintenance it needs. So it is crucial to get this right.

The material should be selected based on local conditions and needs specific to each project, and not, as Ambert points out, based on cost factors. Afterall, the main expense of setting up a pipeline is the trenching work, which generally remains the same regardless of the type of pipe used.

Conducting a thorough assessment of the local environment also enables appropriate measures to protect the pipes to be included in the design, such as using cathodic protection for steel pipes located near power cables and polyethylene-sleeves in corrosive soil areas. Such precautions will lessen the need for remedial repair later. Similarly, pipelines can be routed away from potential contaminants.

After the project blueprint has been drawn up, it is essential to test the design using hydraulic simulation software to check the flow, as pressure affects the pipes’ resistance and the network performance. A well designed and thoroughly tested network should suffer fewer failures and therefore be much easier to maintain.

Ambert also believes a geographic information system (GIS), which holds precise information about the network and its subcomponents, such as valves, connections and pipes to end-users, all of which can all fail, to be essential. “Modern network management needs a good map of the network to manage and reduce leaks,” he says.

Tools of the trade

Once the water distribution network is set up, there are many devices and mechanisms available to assist with pipeline maintenance and the detection of non-visible leaks in particular, such as pressure and flow sensors, acoustic leak detectors, water-sensing cables, leak noise correlation equipment, and ground penetrating radars.

Ambert recommends a combination of methods: “There are many tools available to help with maintenance, but the choice depends on the individual system and local conditions.”

The ideal solution is to avoid the one-size-fits-all approach and opt instead for a customised package that recognises potential weakness in the distribution system, as each operation has its own vulnerabilities. Furthermore, some techniques can be less effective on certain types of pipes, such as acoustic leak detection with plastic pipes.

“You need to make sure you have the correct local tool box,” Ambert advises, “and also that the people using the tools have the necessary know-how to use them. They need to have real expertise in detecting non-revenue water.

Non-revenue water

The main reason water firms invest in this gadgetry and carry out maintenance is to detect water loss and keep the occurrence of non-revenue water (NRW) to a minimum.

The World Bank estimates that globally more than 32 billion m3 of treated water leak from urban water supply systems each year and around 16 billion m3 are delivered to customers for zero revenue. The total annual cost of NRW to water utilities is put at around US $14 billion.

NRW is defined as the volume of water not billed to customers as a share of the total water produced. The lost water can be real, due to leaks, or apparent because of unauthorised consumption or metering inaccuracies. NRW also includes authorised unbilled consumption such as water used for fire fighting.

In some developing countries, NRW can be as much as 40-50% of the total water produced by a network, according to the International Water Association.

High levels of NRW can limit a distribution network’s ability to meet rising demand and can harm the profitability of water utilities by increasing operational costs. Conversely, by reducing NRW volumes, less water is needed to be produced to satisfy demand, meaning utilities can defer capital expenditures to boost supply for longer. Savings are also made on the cost of energy and water treatment. And, more importantly, precious resources of water are not wasted.

In 1997, SUEZ environment’s Moroccan subsidiary Lydec managed to save 20-25 million m3 of water through a leak detection campaign in Casablanca.

Although it is never possible to completely eradicate NRW, Ambert believes water firms need to find an acceptable ratio of non-revenue and revenue-generating water. However, before embarking on a water loss reduction programme a cost-benefit analysis should be carried out to compare cost of saving water from network with value of the water saved. This is because each water distribution system has a level of leakage below which it is not cost effective to make further investment.

NRW can be reduced in two ways. Firstly, by tackling unauthorised or unmetered water usage, through installing more meters, curbing illegal connections, replacing faulty meters and improving water meter management systems. And secondly, by cutting real losses through leakage control, by detecting and repairing leaks from reservoirs, pipes, seals and joints, and through pressure management and infrastructure improvement.

Plug the leak

Leakage management can be classified into two broad groups: passive leakage control and active leakage control. Passive control means responding to reports of leaks or pressure drops, usually from customers. This reactive style of maintenance is sometimes financially justifiable in areas of abundant and cheap water supply.

Active leakage control entails regular methodical surveying of a distribution system, through listening for leaks and monitoring night-flows and leak detection in zones.

Leakage is less of a problem in the UAE than in other parts of the world, as much of the country’s infrastructure was built during the last 50 years. But problems do occur and, as the region has limited natural water supplies, a pipeline maintenance strategy should be seen as essential.

The three main causes of pipeline leaks are ground movement, third party damage – often caused accidentally by construction workers operating nearby, and the failure of the pipe itself – as metals can suffer corrosion and plastic pipes can degrade in heat. Periodic recoating and rust removal of exposed steel pipes is one precaution that can be taken, but preventative maintenance should include frequent line patrols to check pipes, valves and joints as well.

Chemical balance

The lifespan of a pipeline can also be extended by adding de-scaling agents into the water treatment mix, to prevent the build up of scale in the pipe, which can severely restrict the flow and interfere with water pressure.

On top of that, pH correction agents can help to prevent internal corrosion. Integrated water quality monitoring and control systems can also be adapted to include continuous pH measurement in order to detect changes that could lead to corrosion of the network.

Quality repairs

In the event of a pipeline failure, Ambert says masterplanning is also necessary when choosing the method with which to repair a leak. As technology advances, engineers have more repair techniques to choose from, such as tying in new pipes or replacing them in-situ, but again the type of material and manner of repair should be taken on a case-by-case basis and with the aim of providing a long-term solution.

A robust contingency plan should be in place to ensure that a team of experts is always on hand to carry out emergency repairs and that spare parts are in store. “A combination of knowledge and preparation is needed to mend to leak as soon as possible and reduce impact on the pipeline,” Ambert says.

Short-term solutions such as reducing water pressure to prevent a pipe bursting, can, not only result in detriment to the quality of supply to end-users, but may also create a vacuum, which could draw in untreated water and introduce contaminants into the system. Meanwhile, delaying making repairs not only wastes water, but it can also lead to other problems, such as road cave-ins.

Customer care

Not all water losses are the result of poor infrastructure and leaking pipes, however. To be effective in addressing NRW, network and asset maintenance should be accompanied by good customer management, adequate metering and accurate billing, along with a system for storing and comparing data to detect abnormal usage. Even though meters are becoming increasingly sophisticated they need to undergo thorough testing before use and regular checking after installation.

Reaping rewards

Water loss management and leak detection have traditionally been treated as an afterthought. But experience shows that underinvestment in distribution networks is a false economy, as it means treatment plants have to be expanded more frequently in order to keep pace with demand.

Effective pipeline maintenance begins at the planning stage and ends with the customer, making best use of the technology available for the network characteristics. It is essential that a strategy for the upkeep of the network is built into the project from an early stage to avoid additional expense further down the line.

Waiting until a leak occurs before carrying out maintenance is a costly mistake to make, especially as many are non-visible leaks. But it is an all too common practice, as one industry professional observes: “The water industry is unique in that it only does maintenance when something has broken down.

Yet water loss, ultimately, is revenue loss. By maximising distribution efficiency, water companies can maximise revenue. “You need a continuous leak detection system for an effective approach to network management. You should never stop doing it,” Ambert insists.

A cultural shift towards greater proactive maintenance is slowly happening, driven along by technological advances, which make monitoring easier, and by political pressure for improved water efficiency. But in a region where the construction industry is booming, it is still easy to neglect the maintenance needs of hidden infrastructure.

As Bob Smith, business manager for concessions at Metito comments: “There is pressure on construction industry to get pipes into the ground as fast as possible. Only when the situation of a water shortage arises and the cost of water begins to rise, do companies then look at leaks.

“But we need to be careful with water in the Middle East as it is not cheap to produce.”