Page 260 - Water Loss Control

Contr olling Appar ent Losses—Systematic Data Handling Err ors 233

14.4 Determining the Volume of Apparent Loss Due to Systematic
Data Handling Error in Customer Billing Systems
The majority of North American drinking water utilities meter their customers and bill
based upon measured consumption. This is standard practice recommended by AWWA.
However, not all utilities meter their customers, instead these water utilities bill cus-
tomers a flat fee per billing period. Others meter a portion of their customer accounts.
This latter scenario can occur if
• The utility is in transition to a fully metered customer population.
• Utility policies dictate that certain accounts, such as municipal properties or fire
connections, need not be metered.
• Some of the meters are known to be nonfunctional, highly inaccurate or readings
unobtainable, in which case estimates of consumption are used in place of
measured consumption.

Without functional meters in place the water auditor must devise an estimate of the
water consumed by the unmetered population. A number of means exist to develop
reasonable estimates. For instance, in an unmetered system, water meters could be
installed in a small sample of accounts (50 or 100) based upon consumption category or
meter size. Data from these meters could be used to develop average consumption trends
that could be inferred for the entire population in each category. Make certain that any
estimating process that is developed is fully documented and based upon current condi-
tions. Unmetered accounts require the use of estimation, an action which can interject a
degree of error into the measure of customer consumption. For this reason it is highly
recommended that all customer consumption be properly metered, read, and archived.
For water utilities that meter customer consumption, integrity must exist not just
with the accuracy of the meter, but also with the processes to transmit, archive, and
report customer consumption totals as derived from the meter population. An error at
any point in this process potentially represents an apparent loss by distorting the ulti-
mate documented value of customer consumption, causing a portion of the consump-
tion to be understated and possibly missing a portion of revenue. Systematic data-handling
error can therefore occur anywhere from the time that the meter reading is registered to
the final reporting and use of the consumption data.
As discussed in detail in Chap. 13, considerable error can occur in the customer con-
sumption data transfer or meter reading process. Procedures to quantify apparent losses
due to data transfer error, and ways to reduce this form of error, are presented in Chap. 13,
with AMR and advanced metering infrastructure (AMI) highlighted as remarkably
improving technologies that are greatly assisting water utilities in this realm.
Typically meter readings are transferred to customer billing systems where they are
used to calculate the volume of customer consumption occurring since the previous
reading. The consumption volumes are archived and the data is used in the process of
generating water bills and to assist the varied financial operations involved in the rev-
enue collection process. Systematic data handling errors often occur in this process in a
manner that corrupts the integrity of some of the customer consumption volumes.
In the United States consumption is most often recorded in units of cubic feet or
thousand gallons. Billing systems often include programming algorithms that assign
estimates of consumption if an actual meter reading cannot be obtained. These algorithms