Gwinnett County, 30 miles northeast of At- lanta, is one of the state’s fastest growing regions. Currently, Gwinnett County Department of Water Resources (GCDWR) provides services to approximately 240,000 residential and 20,000
commercial/industrial customer accounts.
EVALUATING METER TECHNOLOGIES
Historically, GCDWR installed meter types based on
the application and size of the meter. Standardizing meter
type installations is a common practice among water suppliers. However, a loss of accuracy can be accentuated
at certain fow rates, depending on the meter type. And
some meters lose accuracy over their years in service.
The utility is investigating methods to improve its strategic program for water meters, including a wider selection
of approved metering technologies. The goal is to install
the most appropriate meter for each specifc use and to
enhance the county’s excellent customer service.
A METER COMPARISON TEST CASE
Testing meters for specifc applications and fow
rates is integral to developing this strategic program.
GCDWR selected one of its commercial customers with
a challenging water demand as a test case.
Master Meter had provided the utility with a 3-inch Oc-
tave™ ultrasonic meter, which the utility installed in-line
with a 3-inch compound meter to compare performance.
The test customer maintained an average fow of
27 gallons per minute (gpm), with the lowest fow recorded at 8 gpm and the highest recorded at 42 gpm.
IMPROVED ACCURACY FOR SPECIFIC APPLICATIONS
Initially, manual readings were taken from the meters
each day. These readings indicated consistently higher
usage measurement from the ultrasonic meter.
To enhance the accuracy of the comparison, electronic data-loggers were installed on both meters to
transmit hourly usage logs. Overlaying the fow graphs
from the two meters allowed more in-depth analysis.
The ultrasonic meter consistently registered more usage on average. However, by expanding the low, mid-range, and high-fow sections of the graphs, each meter’s performance at those ranges is evident. At low fows
(0-16 gpm), the ultrasonic meter consistently registered
more fow than the compound meter. Analysis of the
mid-range results showed that the ultrasonic meter also
consistently picked up more accurate registration in the
24 gpm to 32 gpm fow range. Conversely, at ranges of
40 gpm and higher, the compound meter registered very
close to or even higher than the ultrasonic meter.
The similarity of the high-fow accuracies corroborates the meter test results, which showed that both
meters met industry standards. This also indicated that
the data from lower fow ranges was accurate.
Both meters met AWWA standards throughout the
course of the testing. However, for this specifc fow scenario the ultrasonic meter appeared to offer an improvement in
overall accuracy compared to the compound meter.
POTENTIAL FOR ADDITIONAL REVENUE
For the 370-day test period, the total additional fow
registered by the 3-inch ultrasonic meter was about 1. 1
million gallons. Using current commercial water and sewer rates, the unaccounted for revenue during this time
frame would be close to $14,000.
After the comparison test, GCDWR purchased ten additional ultrasonic meters in order to analyze their performance in a variety of fow ranges and confgurations and
the utility has added ultrasonic meter specifcations as
one of the commercial/industrial metering options. WW
To learn more about ultrasonic meters, visit us at www.MasterMeter.com
or call us at (800) 765-6518.
Presented by Master Meter Advertisement
Figure: Assorted daily consumption totals (in U.S. gallons)
demonstrates that the ultrasonic meter appeared to offer an
improvement in overall accuracy when compared to the
Sample Daily Comparison