what is the level in wet well?

Question

a wet well is 4 feet wide and 6 feet long. Approximately how far down should the level in the wet well be lowered in 4 minutes by a pump with a rated capacity of 200 GPM?

Answer 1

In 4 minutes 800 gallons has been drained (4 x 200)

1 gallon = 0.133681 ft³

800 gallon = 106.9448 ft³

106.9448 ft³ / 24 ft² = 4.4560 ft

Answer 2

Assume the well is a circular cylinder, i.e. its cross-section is a circle. It is 4 feet wide, hence its cross-sectional area is 1/4*π*4^2 = 4π feet^2. Let the well level be lowered by f feet by the pump in 4 minutes. The total volume of water pumped out is f*4π feet^3. This also equals 200*4 = 800 gallons. Since 1 gallon = 7.48 feet^3,

f*4π=800/7.48, or f = 8.51 feet. Clearly this is longer than the length of the well, which implies that either the rated capacity of the pump or the dimensions of the well have been assigned incorrect values in the question.