2020-057 2019 Water Loss AuditDate: June 5, 2020 Report No. 2020-057
INFORMAL STAFF REPORT
TO MAYOR AND CITY COUNCIL
SUBJECT:
2019 Water Loss Audit
EXECUTIVE SUMMARY:
Water Utilities staff completes a water loss audit annually in accordance with Texas Water
Development Board (TWDB) regulations and industry best practices. This year’s audit
identified water losses similar to recent years and identified opportunities to improve these
metrics in the future.
BACKGROUND:
TWDB requires the completion of water loss audits annually by all water utilities serving more
than 3,300 customers. Beyond State requirements, a water loss audit program presents
opportunities for better resource conservation and improved fiscal responsibility. For many
years, staff has executed water loss audits to standards over and above TWDB minimum
requirements in pursuit of a healthier water utility. Water loss audit standards within the industry
have continued to evolve, which provides ongoing opportunities for the improvement of
individual audits and has led TWDB to refine their water loss audit framework.
DISCUSSION:
As a primary function, Denton’s water loss audit separates water use into three categories: (1)
authorized consumption, (2) apparent loss, and (3) real loss.
(1) Authorized consumption consists of all water that has been authorized for use by the utility
and its customers. Authorized consumption includes, but is not limited to, water used for
residential and commercial uses, firefighting, municipal landscape watering, pipe flushing, city
offices, and water treatment facility use. Authorized consumption is all the water the utility gave
permission to a business, individual, or itself to use. Staff previously identified an opportunity to
improve water volume estimations for new pipe flushing and is implementing new methods
accordingly.
(2) Apparent loss represents water that was not accurately measured and/or not recorded at a
customer meter and therefore not billed due to meter inaccuracy, theft, and billing waivers. This
category represents a loss in revenue, and since customer meters hold customers accountable for
their water use, it also represents a detriment to water conservation efforts. The water meter
maintenance and replacement program works to offset this loss and maintain reasonable
accuracy in customer meters.
Date: June 5, 2020 Report No. 2020-057
(3) Real loss represents water that left the water distribution system without serving a purpose.
This is largely a result of leakage. Staff estimates water lost through known main breaks and
leaks, and the remaining unaccounted-for volume is assumed to be undiscovered leakage. The
city implemented programs to repair known leaks and search for undiscovered leaks. To the
extent that this program is financially offset by the value of water saved, staff can continue to
reduce real loss through leak detection and repair. The waterline replacement program in Water
Distribution also plays a large part in this figure, as they aim to replace the pipes which are most
likely to break. Staff identified an opportunity to improve water volume estimations on known
water main leaks and breaks and is implementing new steps accordingly.
In a benchmarking study of real and apparent loss, Denton sits near the middle of Region C
utilities in both per connection and per capita measurements as shown below.
Date: June 5, 2020 Report No. 2020-057
The water loss audit framework also includes calculation of the Infrastructure Leakage Index
(ILI), which is a measure of real loss adjusted for the size of each utility. This metric is useful
for benchmarking due to its size considerations. ILI compares real loss to a theoretical
unavoidable leakage unique to each utility based on their size. A value of 1 would suggest a
utility has avoided all possible leakage. There is no upper limit to this metric. Denton’s ILI in
2019 was 2.13, which places us in the top 40% of Region C utilities as shown below.
Date: June 5, 2020 Report No. 2020-057
In the 2019 Water Loss Audit, staff verified existing concerns with the accuracy of large water
meters at Denton’s water production plants. Such accuracy errors have inflated the total amount
of water produced, causing losses to appear to rise over time. Out of the four affected meters,
two have been replaced, and one of the remaining two will be replaced in 2020. Staff is
implementing steps to validate the accuracy of these meters and improve water accounting
within the water production plants. Improved accuracy of these meters will likely result in
reduced estimations of water loss in future audits.
CONCLUSION:
Denton has continued to maintain a competitive water loss management program and has
implemented new steps to continue to improve the program.
ATTACHMENT(S):
Water Audit Presentation 2019.pdf (pptx as pdf)
STAFF CONTACT:
Tyler Dawson, Manager of Asset Management
940-349-8944
Tyler.Dawson@CityofDenton.com
Water Loss Audit
2019
JUNE 8, 2020
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Water Loss Audit
Authorized Consumption
+ Apparent Losses
+ Real Losses
Total Water Supplied
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Water
Produced
Water Exported
Water
Supplied
Authorized
Consumption
Fire Protection
Unbilled
Water Loss
Apparent Loss Unauthorized Consumption
Real Loss
Systematic Data Error
System Operations
The Water Audit Tree –Categorizing Water Use
3
Main Breaks
Unaccounted
Billed
Residential
Commercial
Meter Inaccuracy
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Real Loss
Real loss is water lost through distribution system leakage and
excessive pressure
•Main breaks and leaks
•Undiscovered leakage
•Background leakage
•Other unidentified losses
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Effects of Real Loss
Real losses are indicators of system health
◦These losses should be minimized within economic reason
◦Real losses are priced at the marginal cost of water acquisition and treatment
Denton FY 2019: 607.20 MG/ 9.40%
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Apparent Loss
Apparent loss is water that was not read accurately by a meter
•Water meter inaccuracy
•Unauthorized consumption
•Systematic data errors
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Effects of Apparent Loss
Apparent losses are indicators of fiscal health
◦Inaccurate meters and theft reduce revenue
◦Apparent losses are priced at the retail volume cost of water
Denton FY 2019: 197.42 MG/ 3.09%
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Unbilled Authorized
Fire Protection is provided as an unbilled service
◦Fire sprinkler systems
◦Fire engine use
System operation often requires flushing water mains
◦Cleaning new pipes after installation
◦Removing old water from low flow pipes
◦Flow rate testing and water quality sampling
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Water
Produced
6,476
Water Exported 76
Water
Supplied
6,398
Authorized
Consumption
5,593
Fire Protection 1Unbilled
78
Water Loss
805
Apparent Loss 197 Unauthorized Consumption 16
Real Loss 607
Systematic Data Error 5
System Operations 77
The Water Audit Tree –Categorizing Water Use
9
Main Breaks 40
Unaccounted 567
Billed
5,515
Residential
2,628
Commercial
2,887
Meter Inaccuracy 176
volumes in MG
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Cost of Water Loss
Real Loss -$209,487 / 607.20 MG
◦Real loss is priced at the variable cost of treating 1,000 gallons of water: $0.35
◦Cost of real loss will increase in the future when Denton acquires additions to
the water supply
Apparent loss -$947,621 / 197.42 MG
◦Apparent loss is priced at the average retail cost of 1,000 gallons of water: $4.80
◦This amount is offset by our proactive meter replacement and calibration
program
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Benchmarking Data Points
Real Loss
◦System Health
Apparent Loss
◦Fiscal health
Infrastructure Leakage Index (ILI)
◦Comparison to theoretical minimum leakage
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Benchmarking Considerations
System Size
◦Growth
◦Water Quality / topology
Infrastructure Age
Audit Validation
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13
0
20
40
60
80
100
120
140
Gallons Per Connection Per DayReal and Apparent Loss per Connection Across Region C
Real Loss Apparent Loss
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14
0
5
10
15
20
25
30
35
40
45
Gallons Per Capita Per Day (GPCD)Total Loss per Capita Across Region C
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Infrastructure Leakage Index (ILI)
Calculated as total real losses over theoretical minimum leakage
An indicator of a utility’s effectiveness in managing leaks
Theoretical minimum of 1
◦Denton FY 2019: = 2.13
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16
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
10.00
AWWA Infrastructure Leakage Index (ILI) Across Region C
Infrastructure Leakage Index -Technical Performance Indicator
1.0 –3.0 3.0 –5.0 5.0 –8.0 > 8
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Implementation Steps
✓Continue meter replacement program
✓Continue leak detection program with improved technology
✓Continue use of improved main break water loss estimates
o Improve volume estimates for new line flushing
o Create and implement Mass Balance Worksheet for plants
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Questions / Comments
Water Utilities
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