An inclined tube manometer with a reservoir is used to measure the pressure gradient in a large pipe carrying oil $(\mathrm{SG}=0.91)$ (see Figure $\mathrm{P} 4.5)$. The pipe is inclined at an angle of $60^{\circ}$ to the horizontal, and flow is uphill. The manometer tube is inclined at an angle of $20^{\circ}$ to the horizontal, and the pressure taps on the pipe are $5 \mathrm{in}$. apart. The manometer reservoir diameter is eight times as large as the manometer tube diameter, and the manometer fluid is water. If the manometer reading $(l)$ is $3 \mathrm{in}$. and the displacement of the interface in the reservoir is neglected, what is the pressure drop in the pipe in (a) psi, (b) $\mathrm{Pa}$, (c) in. $\mathrm{H}_{2} \mathrm{O}$ ? What is the percentage error introduced by neglecting the change in elevation of the interface in the reservoir?

FIGURE P4.5

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1 60 0 = 20 2