Page 250 - Water Loss Control

Contr olling Appar ent Losses—Data Transfer Err ors 223

Philadephia Water Department—District Metered Area 5
Night Customer Meter Readings gathered on May 3, 2007 at 2 a.m. and 4 a.m.
3
Total: 1570 ft or 11,744 gal Registered for 2020 Customer Accounts
1,600 1441

1,400
Number of accounts (Italic)
Total consumption, CF (Underlined)
1,200
1,000

800 586 601
383
600 383
400
173
23
200 0
0
Accounts registering Accounts registering Accounts registering Accounts registering
3
zero consumption 1 ft 3 between 2 and 9 ft 3 10 ft or greater
FIGURE 13.22 Customer water consumption in DMA5 during 2 a.m. to 4 a.m. on April 5, 2005;
data used as part of minimum hour assessment of leakage in this DMA. (Source: Philadelphia
Water Department.)

as part of the AWWA Research Foundation project “Leakage Management Technolo-
9
gies.” PWD is believed to be the first water utility in the United States to employ mini-
mum hours AMR readings in a DMA setting to provide a more reliable leakage
assessment. When gathering customer night meter readings, PWD arranges with its
AMR service provider to perform one complete drive-by round of readings in DMA5
around the hour of 2 a.m. A second round of drive-by readings of the +2000 accounts is
gathered around 4 a.m. For each customer account, the 2 a.m. reading is subtracted
from the 4 a.m. reading and any numerical difference calculated as registered consump-
tion for the minimum night period. A distribution of the results from one set of night-
time AMR readings is shown in Fig. 13.22. As might be expected for DMA5, an area that
is largely residential in nature with no industries or irrigation systems using water on a
24-hour basis, water usage is minimal during the 2 a.m. to 4 a.m. period. This is evi-
denced in Fig. 13.22 showing 1441 of 2020 customers, 71% of customer accounts regis-
tered zero consumption and 19% of accounts that registered only 1 cubic foot of water
consumption. Seventy-five percent of the total consumption of 1570 cubic feet was reg-
istered by only 10% of the customer accounts during the 2-hour period. Five accounts
each registered over 40 cubic feet (almost 300 gal) during the 2-hour period, suggesting
leakage in these properties on the customer plumbing. The total customer consumption
for the 2-hour period of 0.141 million gallons per day (mgd) is subtracted from the sup-
ply inflow of 0.55 mgd to infer a difference as leakage in the amount of 0.409 mgd. This
represents a significant amount of leakage which is estimated to exist as one half back-
ground leakage and one half as unreported leaks. PWD is pursuing this leakage by
employing pressure management to address the background leakage and targeted leak
detection surveys to locate and abate the unreported leakage.