Page 100 - Water Loss Control

82 Cha pte r Se v e n

• Illegal connections
• Misuse of fire hydrants and fire-fighting systems, for example, unauthorized
construction use of hydrant water
• Vandalized or bypassed consumption meters
• Corrupt practices of meter readers
• Open boundary valves to external distribution systems (unknown export of water)

The estimation of unauthorized consumption is always a difficult task and should
at least be done in a transparent, component-based way so that the assumptions can
later easily be checked and/or modified if necessary.

Customer Metering Inaccuracies and Data-Handling Errors
The extent of customer meters inaccuracies, namely, under- or overregistration, has to be
established based on tests of a randomly selected representative sample of meters, (AWWA
manuals M6 and M22 provide the relevant guidance). The composition of the sample shall
reflect the various brands and age groups of domestic meters. Tests are done either at the
utility’s own test bench, or by specialized contractors. Large customer meters are usually
tested on site with a test rig. Based on the results of the accuracy tests, average meter inac-
curacy values (as % of metered consumption) will be established for different user groups.
In applying the accuracy test results to the whole population of different user groups
of meters, it is also important to consider the issue of how quickly the utility is able to
identify meters which are totally stopped by considering the utilities processes for identi-
fying stopped meters. The average time taken to identify and replace stopped meters can
have a significant impact on the overall accuracy of the meter population as a whole.
Other issues which are important to consider as part of assessing the level of meter
inaccuracies are
• Meter size in relation to actual use patterns: Are the meters sized correctly to
maximize revenue?
• Meter type: Is it the best type of meter for the operating range?
• Service line size: Is it appropriate for the operating range?

Data-handling errors are sometimes a very substantial component of apparent
losses. Many billing systems are not up to the expectations of the utilities but problems
often remain unrecognized for years. It is possible to detect data-handling errors and
problems within the billing system by exporting billing data (of at last 12 months) and
analyzing it using standard database software. Types of data-handling errors that may
be encountered and should be checked for include
• Changes to consumption volume data when bills are adjusted for any reason
other than an incorrect reading
• Inappropriate use of estimated consumptions
• Inappropriate determination of estimated consumptions
• Accounts incorrectly flagged as inactive
• Accounts missing from the database
• Inaccurate meter data