Theoretical and Conceptual Framework - Pattern Recognition for Reliability Assessment of Water Distribution Networks - page 22

Step 1 : A fully functional network with no pipe failures is analysed. All nodes satisfy the
threshold (i.e. the minimum acceptable pressure) of 20 mwc (MAP). The total demand is
150.75 l/s.
Step 2 : Simulation of the system without pipe 6 in operation shows all nodes to have the
pressure below MAP, calculated in the demand-driven mode. Nodes 3 to 6 have negative
pressures.
Step 3 : All nodes with the pressure below MAP (in this case all in the network) are
transformed into a system consisting of virtual reservoir with the head equal to the sum of
nodal elevation and MAP. Each reservoir is connected with short pipe containing a non-
return valve to prevent the backflow from the reservoir. To assess the actual demand, the
original nodal demand has been set to zero.
Figure 2.5 Steps for calculation of ADF (Yoo et al., 2005)