Real Loss Overviews

4 Components Approach to Managing Water Leakage

How to Squeeze the Leakage Box

The first version of this widely used diagram was developed by Pearson in 1995, and it has since been further enhanced to include economic leakage levels. It is now widely used internationally as a simple means of explaining the four basic activities that are required for effective operational management of Real Losses.

The first version of this widely used diagram was developed by Pearson in 1995, and it has since been further enhanced to include economic leakage levels.

Suppose that the area of the large rectangle represents the Current Annual Real Losses, in volume per year, for any specific system. As the system ages, new leaks and bursts (background, reported and unreported) will occur, causing the large rectangle to expand in size, unless existing and new leaks can be controlled and managed by some appropriate combination of the four primary components of Real Losses Management (shown as blue arrows on each of the four sides of the large rectangle).

The frequency and flow rates of new leaks arising each year are influenced primarily by Pipeline and Assets Management, and the effectiveness of Pressure Management (which may involve increase or decrease of pressure). The average duration of reported leaks is limited by the Speed and Quality of Repairs, and the Active Leakage Control strategy determines the ‘awareness + location’ time of unreported leaks before they are repaired. The extent to which each of these four activities is carried out will determine whether the volume of annual Real Losses increases, decreases or remains constant.

Note that all four activities are necessary to prevent real losses from increasing. If the only activities carried out are repair of reported leaks and some asset management, then in the absence of active leakage control the unreported leaks will accumulate and the right hand side of the large rectangle will expand. Similarly, if not all reported leaks are repaired, the left hand side will increase.

The small yellow rectangle showing Unavoidable Annual Real Losses (UARL), calculated using an IWA formula, represents an estimate of the lowest technically achievable real losses at the current operating pressure. Calculation of the Infrastructure Leakage Index (ILI), which is the Current Annual Real Losses (large rectangle area) divided by the UARL rectangle area), will quickly provide an overview of the overall effectiveness of real losses management, using the International Leakage Classification Performance System (A1 to D2) shown near the end of the UARL and ILI webpage.

If each of the four management components is applied at an economic level of activity (with priority being given to those with the quickest payback period or highest benefit:cost ratio), the Real Losses volume should eventually reduce to an economic level of Real Losses (shown as an orange rectangle). This technique is known as ‘squeezing the box’.

At the 2002 IWA Conference ‘Leakage Management – A Practical Approach’, Lambert & McKenzie emphasised that the ILI measures how well real losses are being managed at the current pressure; but if the current pressure regime is not optimal, there are often pressure management options that will have additional substantial benefits in terms of reductions in leak flow rates, new burst frequencies, repair costs and other benefits.

The modified 4-Component diagram below shows how pressure management can influence the other 3 leakage management components. Reductions in excess pressure not only reduce leak flow rates (FAVAD NI), especially background leakage; by reducing new leak frequency, the rate of rise of unreported leakage is reduced (requiring less frequent ALC interventions) and the number and run-time of reported leaks and bursts is also reduced. Fewer bursts lead to extended infrastructure life, and improved Pipeline and Assets Management.

This modified 4-Component diagram shows how pressure management can influence the other 3 leakage management components

For more information on these topics link to Economic Intervention, Pressure and Bursts, and Economic Leakage.