Page 162 - Water Loss Control

140 Cha pte r T e n

Flow Rate for Reported Breaks Flow Rate for Unreported
Location of Break [gal/hr/psi pressure] Breaks [gal/hr/psi pressure]
Mains 44 22
Service connection 6 6

Source: Julian Thornton, Reinhard Sturm, George Kunkel, P.E

TABLE 10.8 Example Reported and Unreported Leakage Flow Rates

Location duration: For reported leaks and breaks, this is the time it takes for the
water utility to investigate the report of a leak or break and to correctly locate its
position so that a repair can be effected; for unreported leaks and breaks, the
location duration is zero since the leak or break is detected during the leak detection
survey and awareness and location occur simultaneously.
Repair duration: The time it takes to make the repair or shut off once a leak has been
located.

The overall volume of water lost through each running break and leak is deter-
mined from the overall time of these three components and the flow rate of the leak at
the current system pressure. This is shown graphically in Chap. 17.
The water balance calculates the total volume of real losses for the audit year. How-
ever, it does not provide the information on what portion of these real losses is due to
background losses, reported losses, and unreported losses.
By assessing the volume of real losses through component-based analysis, it is pos-
sible to model the volume of real losses that are due to each component and identify
suitable tools for their reduction.
A more in-depth analysis of components of real loss may include an analysis of the
frequency of breaks on different system components against the baseline UARL fre-
quencies, which in conjunction with measured ICF values might help to dictate the
longer term need for infrastructure replacement.

10.6.2 Analyzing the Effects of Changing System Pressure—FAVAD
and BFF Concepts
Pressure management can be used to mitigate the adverse effects of excess pressure in
a distribution system. Later in Chap. 12, we will be addressing pressure management as
a means of controlling leak volumes, reducing leak frequency, and reducing wasteful
consumption, as part of a water conservation strategy. However, prior to installing
pressure-management systems it is important to understand the effects of our control.

10.6.3 Modeling the Effects of Changing System Pressure on
Leakage Flow Rates and Volumes Using FAVAD

Predicting the Reduction in Break Flow Rates
3
Theoretical hydraulics tells us that the equation for fully turbulent flow Q through a
f
fixed orifice of area A at static head h follows the square root principle, whereby Q is
f f