Prob. $8\mathrm{.}5\mathrm{.}7$ p$.$ IP$-108[$Ans: $0\mathrm{.}0388$;$0\mathrm{.}75$ psi$].$

$8\mathrm{.}5\mathrm{.}7$ WP Video As shown in Video V$8\mathrm{.}15$ and Fig. P$8\mathrm{.}5\mathrm{.}7,$ water "bubbles up$"3$ in$.$ above the exit of the vertical pipe attached to three horizontal pipe segments. The total length of the $0\mathrm{.}75-$in$.-$diameter galvanized iron pipe between point $(1)$ and the exit is $21in.$ Determine the pressure needed at point $(1)$ to produce this flow.