Page 207 - Water Loss Control

Contr olling Appar ent Losses—Customer Meter Inaccuracy 181

Meter downsizing decisions should be approached with sensitivity when it appears
that a reduced service charge makes the downsizing decision uneconomic for the water
utility. Keeping a customer account with an oversized meter means that the recorded
flow remains understated and the apparent loss is not reduced. Also, it becomes evi-
dent that the customer is paying a higher service charge than necessary since they could
function (more accurately) with a smaller water meter. Water utilities that specifically
avoid downsizing in this manner risk customer dissatisfaction should this information
reach the customer. If many customers perceive that they are being overcharged by the
water utility, a public relations backlash could result in negative media attention or
fines if such actions violate any regulations. If the water utility manager maintains a
“big picture” perspective of the value of meter accuracy and apparent loss reduction, he
or she can tolerate the uneconomic downsizings of some large meters in order to pro-
vide equity to its customers and strive to optimize its apparent loss reduction from
meter sizing improvements.
Meter right-sizing initiatives typically address large meters in settings where cus-
tomer consumption patterns have changed due to building occupancy changes, or
where an inappropriately selected or sized meter was originally installed. However,
accurate and reliable small meters also incur low flow limitations in which a portion of
flow is not registered. No meter is 100% accurate. While most meters have limitations
only at very low flow rates, such unregistered flows can occur in hundreds or thou-
sands of customer meters in a water utility, therefore the cumulative volume of unmea-
sured water can be significant. A common occurrence in North America is of flows
below detectable limits (BDL) occuring from toilet leaks. Slight leaks in toilet flapper
valves allow a continuous trickle of water to pass into the toilet and drain to waste. It is
very common that these flows are so slight as not to be registered by many reliable
brands of water meters. A similar low-flow condition has been documented in Europe
in communities where it is common for individual buildings to have small roof tanks.
The slow closing of ball valves included in the roof tanks results in flows that are lower
than the starting flow of the customer water meter. One device that has been created to
address metering low flow limitations is the unmeasured-flow reducer (UFR) which
changes the flow regime passing through the water meter to batches that the water
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meter can measure. In this way, only flow rates that are sufficient to be registered by
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the meter are passed through the meter. Innovations in meter technology, data-logging,
AMR, and devices such as the UFR continue to offer water utilities the means to mea-
sure water consumption with ever-improving accuracy. It is incumbent on the water
utility manager, however, to assess the overall accuracy and reliability of their customer
meter population and seek to improve where needed.

12.5 Developing the Customer Meter Accuracy Testing Program
In order to assess and maintain good physical accuracy of the customer meter population,
many water utilities operate their own meter test facility and equipment, and perform
ongoing accuracy testing of meters that have been rotated out of service. For these opera-
tions, testing of targeted groups of meters can be readily accommodated. Water utilities
that do not have their own facilities can outsource their testing to specialty companies.
Total customer consumption meter error includes meter errors from all meter sizes,
including residential, industrial, commercial, agriculture, and others. In general, meter
error can be assessed for small meters (5/8 in and 3/4 in), which are typically employed