--say 7,575 gallons. But a flow of 15,555 gallons per minute is
required, as it varies approximately as the fifth power of the
diameter, the requisite diameter will be about

[*Math: \sqrt[5]{\frac{30^5 \times 15,555}{7575}] = 34.64
inches.

Now assume a diameter of 40 in, and repeat the calculations.
Then head necessary to produce velocity

[*Math: = \frac{15,555^2}{215 \times 40^4}] = 0.044 ft, and
head to overcome friction =

[*Math: \frac{15,555^2 \times 2042}{240 \times 40^5}]

= 20.104 ft Then 0.044 + 20.104 = 20.148, say 20.15 ft, and the
true flow will therefore be about

[*Math: 15,555 * \sqrt{\frac{20.42}{20.15}}]

= 15,659 gallons, and the requisite diameter about

[*Math: \sqrt[5]{\frac{40^5 * 15,555}{15,659}}]

= 39.94 inches.

When, therefore, a 30 in diameter pipe is assumed, a diameter
of 34.64 in is shown to be required, and when 40 in is assumed
39.94 in is indicated.