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The SANFLOW model was used to partition UFW into real and APL from the analysis of MNFs obtained from flow logging. The lowest flows occurring between 12 a.m. and 4 a.m. were taken as MNFs in the analysis, as proposed by Thornton et al. (2008). Although customer demand is minimal at night, there is still a small amount of flow in the system owing to night-time customer demand for such uses as toilet flushing, washing machines and any other night use. In urban situations, about 6% of the population will be active during the minimum night-time flow period (McKenzie 1999). Equations (1)–(3) explain how RL are computed from MNFs. Apart from the MNF data, the SANFLOW model also requires basic infrastructure variables which are presented in Tables 1 and 2.

Table 1

Infrastructure variables used in SANFLOW model

Infrastructure variableArea 15Area 18Area 28
Length of mains (km) 6.8 39.62 10.83 
Number of connections 278 2,240 141 
Number of properties 278 2,240 141 
Estimated population 2,124 18,846 8,063a 
Density of users per km of mains 41 57 13.3 
Infrastructure variableArea 15Area 18Area 28
Length of mains (km) 6.8 39.62 10.83 
Number of connections 278 2,240 141 
Number of properties 278 2,240 141 
Estimated population 2,124 18,846 8,063a 
Density of users per km of mains 41 57 13.3 

Note: The infrastructure variables are based on actual data in the areas from utility records.

aPopulation for Area 28 is the equivalent population obtained from average consumption for Area 28 and average per capita consumption for Area 18 (i.e., population it could serve assuming it was also a residential area with per capita consumption similar to that of Area 18).

Table 2

Leakage parameters used in SANFLOW model as recommended by McKenzie (1999) 

DescriptionDefaultArea 15Area 18Area 28
Background losses from mains (L/km.hr) 40 40 40 40 
Background losses from connections (L/conn.hr) 
Background losses from properties (L/conn.hr) 
% of population active during night 
Quantity of water used in a cistern (L) 10 10 10 10 
Background losses pressure exponent 1.5 1.5 1.5 1.5 
Burst/leaks pressure exponent 0.5 0.5 0.5 0.5 
Average use for small non-domestic users (L/h) 50 50 50 50 
Use by large non-domestic users (m3/h) 1.2 1.2 1.2 3a 
DescriptionDefaultArea 15Area 18Area 28
Background losses from mains (L/km.hr) 40 40 40 40 
Background losses from connections (L/conn.hr) 
Background losses from properties (L/conn.hr) 
% of population active during night 
Quantity of water used in a cistern (L) 10 10 10 10 
Background losses pressure exponent 1.5 1.5 1.5 1.5 
Burst/leaks pressure exponent 0.5 0.5 0.5 0.5 
Average use for small non-domestic users (L/h) 50 50 50 50 
Use by large non-domestic users (m3/h) 1.2 1.2 1.2 3a 

aEstimate based on McKenzie (1999) who established an average 20.5 L/property.h of this loss parameter (i.e., 20.5/1,000*141).

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