Page 108 - Water Loss Control

90 Cha pte r Se v e n

Performance
Function Ref. Level Indicator Comments
Financial: Fi36 1 (basic) Volume of nonrevenue Can be calculated from
nonrevenue water as % of system simple water balance
water by volume input volume
Financial: Fi37 3 (detailed) Value of nonrevenue Allows different unit
nonrevenue water as % of annual costs for nonrevenue
water by cost cost of running system water components
Inefficiency of WR1 1 (basic) Real losses as a % of Unsuitable for
use of water system input volume assessing efficiency
resources of management of
distribution systems
Operational: Op24 1 (basic) gal/service line/d, Best “traditional” basic
real losses when system is performance indicator
pressurized
Operational: Op25 3 (detailed) Infrastructure leakage Ratio of current annual
real losses index real losses to unavoidable
annual real losses

Source: Ref. 7.
TABLE 7.4 IWA Recommended Performance Indicators for Nonrevenue Water and Water Losses

• Level 2 (intermediate): Additional indicators, which provide a better insight than
the Level 1 indicators for users who need to go further in depth.
• Level 3 (detailed): Indicators that provide the greatest amount of specific detail,
but are still relevant at the top management level.

Particular points to note from the Table 7.4 are as follows:
• Fi36: Percentage of nonrevenue water is the basic financial PI.
• Fi37: This detailed financial PI is a development of a 1996 recommendation of
the AWWA Leak Detection and Water Accountability Committee.
• WR1: Real losses as percentage are unsuitable for assessing efficiency of
management of distribution systems for control of real losses, because of the
influence of consumption.
• Op24: Gallons/service line/d is the most reliable of the traditional PIs for real
losses, for all systems with service line densities of > 32/mile.
• To improve on Op24, take account of three key system-specific factors: Density of
service connections, location of customer meter relative to curbstop, average
operating pressure.

N OT E :
NOTE: By expressing Op 24 as “Gallons/service line/d/psi of pressure,” the influence of
pressure is included.
• Op25: The infrastructure leakage index (ILI) is a measure of how well the system
is being managed for the control of real losses, at the current operating pressure.