2019-082 2018 Water Loss AuditDate: April 19, 2019 Report No. 2018-082
INFORMAL STAFF REPORT
TO MAYOR AND CITY COUNCIL
SUBJECT:
2018 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 over and above TWDB standards 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:
authorized consumption, apparent loss, and real loss.
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 identified an opportunity to improve water volume
estimations for new pipe flushing and is implementing new methods accordingly.
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 program works to offset this loss and maintain reasonable accuracy in customer
meters.
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 has
implemented programs to both 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
Date: April 19, 2019 Report No. 2018-082
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 in the middle of Region C utilities
in both per connection and per capita measurements as shown below.
Date: April 19, 2019 Report No. 2018-082
The water loss audit framework also includes 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 2018 was 1.83, which places us
within the lowest 25% of Region C utilities as shown below.
In the 2018 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 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.
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 2018.pdf (pptx as pdf)
Date: April 19, 2019 Report No. 2018-082
STAFF CONTACT:
Tyler Dawson
Water and Wastewater Field Service Technical Manager
940-379-8944
Tyler.Dawson@CityofDenton.com
Water Loss Audit
FY 2018
1
Water Loss Audit
Authorized Consumption
+ Apparent Losses
+ Real Losses
Total Water Supplied
2
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
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
4
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 2018: 505 MG/ 7.27%
5
Apparent Loss
Apparent loss is water that was not read
accurately by a meter
•Water meter inaccuracy
•Unauthorized consumption
•Systematic data errors
6
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 2018: 222 MG/ 3.19%
7
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
8
Water
Produced
6,946
Water Exported 73
Water
Supplied
6,873
Authorized
Consumption
6,147
Fire Protection 1Unbilled
50
Water Loss
727
Apparent
Loss 222 Unauthorized Consumption 17
Real
Loss 505
Systematic Data Error 5
System Operations 49
The Water Audit Tree –Categorizing Water Use
9
Main Breaks 3
Unaccounted 502
Billed
6,097
Residential
3,026
Commercial
3,071
Meter Inaccuracy 199
volumes in MG
Cost of Water Loss
•Real Loss -$188,496/ 505.31 MG
–Real loss is priced at the variable cost of treating 1,000
gallons of water: $0.37
–Cost of real loss will increase in the future when Denton
acquires additions to the water supply
•Apparent loss -$1,039,605 / 221.66 MG
–Apparent loss is priced at the average retail cost of 1,000
gallons of water: $4.69
–This amount is offset by our proactive meter replacement
and calibration program
10
Benchmarking Data Points
•Real Loss
–System Health
•Apparent Loss
–Fiscal health
•Infrastructure Leakage Index (ILI)
–Comparison to theoretical minimum leakage
11
Benchmarking Considerations
•System Size
–Growth
–Water Quality / topology
•Infrastructure Age
•Audit Validation
12
13
0
20
40
60
80
100
120
CelinaSardis Lone ElmHighland ParkCarrolltonRowlettBalch SpringsDuncanvilleBenbrook Water AuthoritySachseMountain Peak SUDThe ColonyLake Cities M.U.A.IrvingKellerLittle ElmWeatherfordCorinthDenisonFarmers BranchLewisvilleDallas Water UtilityShermanCrowleyDentonGarlandForneyAllenCedar HillAddisonFairviewGrand PrairieCorsicanaTerrellBonhamDesotoFort WorthRichardsonPlanoMcKinneyAthensGallons Per Connection Per DayReal and Apparent Loss per Connection Across Region C
Real Loss Apparent Loss
14
0
10
20
30
40
50
60
RowlettDuncanvilleCarrolltonBalch SpringsLake Cities MunicipalDallas Water UtilitySachseLittle ElmKellerHighland ParkCorinthThe ColonyAddisonIrvingWeatherfordBenbrook Water AuthorityDentonDenisonForneyCedar HillGarlandCelinaLewisvilleAllenCrowleyFarmers BranchShermanSardis Lone Elm WSCGrand PrairieBonhamTerrellFort WorthDesotoPlanoRichardsonCorsicanaMcKinneyFairviewAthensMountain Peak SUDGallons Per Capita Per Day (GPCD)Total Loss per Capita Across Region C
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 2018: = 1.83
15
16
0
1
2
3
4
5
6
7
8
9
Infrastructure Leakage Index (ILI) Across Region C
Implementation Steps
•Ongoing meter replacement program
•Ongoing leak detection program with
improved technology
•Improved main break water loss estimates
•Improved water use estimates from
operational applications
•Improved source metering at water
production plants
17
Water Loss Audit
FY 2018
18