Page 210 - Water Loss Control

184 Cha pte r T w e l v e

50% of revenue is received from less than 20% of customers accounts with large meters.
Therefore it is critical that these accounts are systematically reviewed to ensure that
they are being metered and billed correctly. Large meters should be inspected for proper
selection and sizing before installation. Additionally, large meters should be tested for
accuracy before they are used, since not all new meters are sufficiently accurate. In the
United States, meters sized 1 in and larger are typically considered to be large meters,
although the specific size convention can vary from one utility to another.
All water utilities, regardless of their number of customer accounts, should strive to
regularly inspect, test, and confirm appropriate sizing for the relatively small number
of meters serving the largest of water consumers. These meters provide the basis for the
largest billings in the water utility and every effort must be made to keep them accurate.
Inspecting and testing the top 10 largest users in the system on an annual basis will help
ensure that optimal customer billings are occurring. Ideally, a representative segment of
the large meter population should be tested each year, including 1- , 1½- , and 2-in
meters, a mid-range that sometimes is overlooked by utilities.
Tables 12.6 to 12.8 illustrate the use of meter test data to calculate total large meter
1
error. The mean registration data in Table 12.6 are used to calculate the meter error for
large meters. The actual test results are shown in Table 12.7 and the resulting large
meter error for County Water Company is shown in Table 12.8 as 29.97 million gal. The
results of the individual large meter tests can be used to estimate the amount of revenue
to be gained by improving the function of large meters by applying the appropriate cost
factor.

12.5.1 Customer Meter Accuracy Testing: Methods and Procedures
Most water meters are mechanical devices. As such they wear and lose accuracy after
an extended period of operation. Unfortunately, many water utilities do not carefully
track the overall accuracy of their customer meters, resulting in unchecked, growing
apparent losses and their negative impacts. Small meters of size less than 1 in are usu-
ally applied in residential applications and have distinct advantages in testing since one
worker can easily remove and replace (rotate) the old meter and test it away from the
customer location: at the water utility test bench or that of a meter testing contractor. By
using this approach, water utilities ensure speedy service to their customers at their
premises and accurate testing of meters at a controlled testing site. Many water utilities
have moved away from testing small water meters at the installation site, just as they
have moved away from repairing these meters. Old meters rotated out of customer
properties and tested at the utility test facility provide meter accuracy data that allows

Flow Rates Percent of Volume Delivered
Low 10
Medium 65
High 25

* For this example, assume flow recordings were made for 24 hours in July and February to derive the
percent of volume registered by large meters at low, medium, and high flow rates.
Source: Ref. 1
TABLE 12.6 Volume Percentages for Large Meters for County Water Company ∗