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Contr olling Real Losses in the Field—Pr oactive Leak Detection 291

include in the night flow analysis. Household night water use can be determined
by gathering data through manual or fixed network automatic meter readings
during the minimum nighttime consumption period, or through deployment of
data-loggers recording the household night use. Alternatively, data from the
literature can be used, for example, the U.K. Managing Leakage Series provides
details of assessed night use studies in the U.K. between 1991 and 1993 and the
AWWA Research Foundation project residential end uses of water (REUWS)
provides data on North American night use volumes. If there is significant
nighttime landscape irrigation consumption at certain times during the year, it is
recommended to undertake DMA MNF analysis during periods of no irrigation
or when irrigation is at a minimum, usually during the winter period.

16.6.7 Prioritizing DMA Leak Detection Efforts
DMAs allow assessment of leakage volumes in a hydraulically discrete zone. If multiple
DMAs are established in the service area, leakage volumes can be assessed for each of
the DMAs on a regular basis. The results gained from the DMA measurements allow a utility
to prioritize its leak detection efforts, targeting the DMA(s) with the highest leakage volume,
where the leak detection efforts bring the best results in real loss reduction in relation to the
work effort required. Consequentially, targets can be set to decide which DMA needs to be
addressed and in what order by the leak detection team. A simple starting point for pri-
oritization of leak detection efforts is to rank DMAs according to their volume of real losses
per service connection. This applies to utilities in urban areas, while rural utilities should con-
sider expressing the volume of real losses by length of main. The use of DMAs results in a
strategic scheduling of leak detection crew activities. This is more efficient that the historic
practice of crews canvassing portions of the service area based upon fixed time intervals.
Ideally targets, or thresholds, for leak detection intervention are set based on analy-
sis of the economic optimum volume of leakage in each DMA (see Fig. 16.19).

Intervention in DMA Based on Night Flow

Intervention level

Night flow m 3 /hr Exit level

Sum of background leakage & assessed
customer night use

0 20 40 60 80 100 120 140 160 180
Time in days
FIGURE 16.19 Example for leak detection intervention level based on economic optimum
analysis of real loss volumes in a DMA. (Source: IWA Water Loss Task Force.)