If it's really leaking, just go and find it
If you know what you are looking for it is much easier to find it. A pretty obvious statement, but one that is not always applied as far as leak detection is concerned explains Geoff Pook, managing director of All Water Technology.The basic information required to efficiently manage and direct leak detection work is available from a properly set up and maintained DMA monitoring system. In many instances however, the very information required to efficiently direct detection work and measure its effectiveness either doesn¹t exist or is inaccurate. To be fair nearly all water companies have either set up DMA systems or are in the process of setting them up and the magnitude of this task should not be underestimated.
These factors are based on the characteristics of the infrastructure and the operating criterion of the system. When applied generally they can provide a useful background explanation and understanding of leakage levels in the whole system. However, they do nothing to find the specific leak or reduce real leakage. Appreciation of system weakness or the possible cause of leakage can help to guide the overall approach but it should not be used to determine the specific approach.
Intrinsically leak detection is not difficult and good results should be achievable through the systematic application of basic methods utilising good data and appropriate technology. Statistics can be used to prove almost anything and can obscure what are fundamentally simple problems. When it comes down to fundamentals, what can be simpler than measuring what goes in and taking away what goes out and what is legitimately used.
A high nightline may be explained away by infrastructure factors and average allowances, in practice hoever the most probable explanation, is a small number of actual leaks. In this case, the only way to reduce the overall leakage is to go and find the specific leaks. The methods available are not new; sounding, correlation and step testing to name a few are applied systematically and consistently in the field.
These approaches undirected can be inefficient and expensive. The efficiencies can only be achieved if the fieldwork is efficiently directed to eliminate unnecessary work and target the effort and this can only be achieved through accurate monitoring via the DMA structure.
Leak detection although being given higher priority is being made more difficult through the application of new regulations and working practices. The step test is a key tool and is very efficient in localising and quantifying leaks. Water quality issues are these days restricting its application almost to the point where it is being eliminated as a tool. While the water quality issues are important a compromise should be reached to allow the engineer, whether in-house or a contractor, to use all the tools available to them to drive down leakage. Rather than ban a proven method of leak detection because it causes problems of discoloration, the causes and symptoms should be managed. Basically this means managing a notification procedure and managing a flushing procedure standard industry procedures and not exactly high technology. The problem in the majority of cases is not the discoloured water but the lack of communication with the customers.
From the contractors' perspective, detection work is much more effective and satisfying when looking for known leakage that is accurately eliminated, using their full range of skills and when results can be positively demonstrated.
Recent contract successes have proven the value of good information. All Water Technology has worked in Sutton and East Surrey since 1993, has undertaken practically all South West Water¹s leak detection since 1995 and recently completed a combined leak detection and management of repair contract for the Isle of Man Water Authority.
The majority of this work has been on a payment by results basis that demands good accurate data from the client. Working in this method delivers a twofold benefit to the client. The contractor uses the information to efficiently target the detection effort but also examines, and tests information and data more rigorously and is required to understand the working of the system in more detail than might otherwise be the case.
The approach is to confirm information and where necessary, amend it, to ensure the DMA is reporting accurately. Once the accuracy of the reporting is confirmed the contractor can confidently go about his job of finding real leakage. In any event the end result for the client will be reduced leakage, an accurate DMA and more accurate GIS records.
Sutton and East Surrey Water has had one of the most comprehensive real time monitoring systems of all companies. The DMA set up covers the while of the companies operating area. All loggers are connected to the central control by modem and are polled every night. This provides data on a daily basis enabling detection work to be directed almost immediately, reducing the interval between occurrence and detection and therefore the volume of water lost.
The added advantage of daily data is that the in-situ equipment can be used more readily as an analysis tool. Coarse step tests can be carried out without having to set up special loggers or meters, allowing the site teams concentrate on the on-site organisation. Leaks located can be quantified in order to prioritise repairs and the effort of specific repairs can be appreciated immediately, enabling the programme of work to be amended accordingly if the results have been achieved. All data is available the next morning back at base to be analysed and acted upon.
The benefits of a properly set up, well-proven DMA system are enormous and
give the engineer the information to manage the resources in the most
efficient manner. On a local scale, the basic flow data, less known and
accepted allowances, is all that is needed to direct leak detection. If the
night flow is higher than can be accounted for, forget the Œfactors' give
the detection teams accurate information and the tools to do the job, and
just go and find the leaks.