Reducing Non Revenue Water
According to the International Water Association, the definition of Non Revenue Water is “the difference between system input volume and billed authorized consumption”, and it consists of the following:
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Unbilled Authorised Consumption (usually a minor component of water balance),
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Apparent Losses (including unbilled unauthorised consumption), and
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Real Losses (e.g. from leaking pipes).
This is a particular problem in Asia, where consumers have expressed anger that a precious and scarce resource is being wasted, whilst they are paying for inefficient water utilities.
The combination of physical leaks, plus water taken from the system is, unfortunately, a feature of many systems.
From the consumers’ point of view, those who have illegal connections or have estimated actual consumption below real consumption are cheating the system.
But, how do you tackle such a significant problem. A six point philosophy is suggested:
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Understand every system – especially through quality asset management systems and more effective hydraulic monitoring
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Provide quality data on each component of Non Revenue Water
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Establish physical and apparent losses
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Focus on the largest Non Revenue Water losses first
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Fix apparent losses or quantify the extent of loss
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Manage the real losses through
- Active leakage control
- Speed and quality of repairs
- Pipe quality, selection, renewal etc
- Understanding the structural condition of assets and likelihood of failure and potential water losses
- Developing an efficient “prevent fail” program
- Pressure management.
- Operational management (e.g. to prevent bursts from pressure surges)
There is a need to separate real physical losses from apparent non physical losses.
Apparent losses are due to errors in data collection, transfer and management techniques. They also include unbilled, unauthorised consumption from the water supply system.
These apparent losses often exceed the real physical losses.
Sadly, there will always be some unavoidable loss, in the order of 5-10%. This is because it is uneconomic in some cases to identify the exact source of the losses and/or the costs of taking remedial or preventative action to recover or prevent the water losses exceeds the benefits.
To counter this, there is a need to collect quality data. This involves the installation across a utility area of accurate meters supported by best practice calibration techniques (initial and repeat calibrations).
100% of the area needs to be correctly metered, particularly the larger customers. Accuracy is a key issue. A water authority must be prepared to make the investment in meters of sufficient accuracy. Often such initiatives are self-funding or have short payback periods.
Meters should be cross checked for accuracy and calibrated, and consideration should be given to renewing your stock of meters, because old meters are slow meters, and low flows tend to be under recorded.
The automatic collection and transmittal of this data tends to be more reliable than manual techniques.
Using a GIS and asset database to store the information is critical to success. These tools allow managers to overlay all the mains on a base map, with the potential to identify key features an assist in assessment techniques fro identifying areas at greater risk of leakage.
But, don’t think that the installation of a GIS will be the solution to all of your problems. It must be properly maintained.
There are a number of examples where this strategy has proved to be highly successful. For example, in Sao Paulo, Brazil, 27,000 of that city’s bulk meters were replaced, where the majority (some 80%) were oversized. Oversized meters will under record water usage. Following a trial of 354 new meters, it was found that only 70% were oversized, providing a payback to the utility within two months.
In Germany, water authorities have been remotely reading water and energy for apartment buildings for some time. Data is collected every four to six hours. This provides accurate and transparent systems for the water utility, landlords and tenants, while also quickly identifying any faults or leaks.
The key to success, however, is in the institutional arrangements that each water area or utility puts in place.
You must be prepared to enforce laws/regulations, both through physical or legal proceedings, and without any any loopholes. The staged response to non payment – needs to be documented and followed.
Importantly, you must have the power to disconnect, restrict to a dribble, fine or take legal action, particularly for those responsible for tampering with or by-passing meters.
A leading edge approach to investigations is strongly suggested, with the accurate recording and response to the notification of any leakage to individual customers is vital.
You should consider the establishment of call centres to take information on leaks from consumers, with a system to grade each incident and response.
A strategy to use the media as a way in which to garner community support, along with information on the action that is being taken, is worthwhile.
A good investigation should be able to identify those elements of the system that are most prone to failure. Information on the location, asset’s age, pipe type, soil type and proximity to other assets should be collected. There will be a significant number of assets, so large inspections and renewals have to be targeted and prioritised, while developing different strategies for critical water mains and reticulation mains.
You should also consider noise analyses to identify leaks, along with physical inspections. This can include the use of acoustic logging systems and tracer gas.
Finally, a good decision making framework based on a best practice approach to asset management will prove to be invaluable as you begin to target non revenue water looses.
Start by developing a Decision Making Framework with a clear and unambiguous set of business rules, including technical and economic/financial rules that can be used to govern investments and to prioritise data collection, investigations and works programs (renewal and rehabilitation).
With this in place, you can start to establish a rationale behind the financial and economic costs of particular events, and make it part of the decision process, such as the cost of detection versus the impact of failure.
In the long run, the strategy you put in place is likely to save your organisation a great deal of money.
© Sinclair Knight Merz
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