The layout of a loop in a water distribution system is shown in Fig XXXXXXXXXXAll pipes of the gridiron network have the same elevation and a Hazen–Williams C of 100. The grid ABCDA serves an area...

The layout of a loop in a water distribution system is shown in Fig. 6.33. All pipes of the gridiron network have the same elevation and a Hazen–Williams C of 100. The grid ABCDA serves an area that requires a design fire flow of 9,000 gpm. The pressure in the primary feeders ABCDA is 30 psi, and the fire hose lines available are 410 ft long. Supposing there is a fire at the middle of the grid (point X),

(a) Find the residual pressure at the hydrants.

(b) How many lines (minimum) should be changed from 8 in. to 10 in. in order to maintain a residual pressure of at least 20 psi at the hydrants?