1. In a lift station with a diameter of 10 feet, you are able to lower the water level 6 inches in 2 minutes. What is the pumping rate in gallons per minute?

2. What is the pumping rate, in gallons per minute, if you are wasting sludge to a 20-ft diameter tank and the depth increases 3 inches in 20 minutes?

3. A pump lowers the water level 3 feet in 30 minutes to a wet well that is 15 feet by 12 feet. If no influent flow is coming into the wet well, what is the pumping rate in gallons per minute?

Answers:

1. 146.8 gal/min

Do conversions: Don’t use diameter – radius is 1/2 diameter (10 ft) / (2) = 5 ft radius

(6 inches) / (12 in/ft) = 0.5 ft

Find Cubic Feet 3.14 X 5 ft X 5 ft X 0.5 ft = 39.25 cuft

Find Gallons 39.25 cuft X 7.48 gal/cuft = 293.59 gallons

Find how many Gallons per Minute (239.59 gal) / (2 minutes) =

2. 29.36 gal/min

Do conversions: (20 ft) / (2) = 10 ft radius, (3 in) / (12 in/ft) = 0.25 ft

Find Cubic Feet 3.14 X 10 ft X 10 ft X 0.25 ft = 78.5 cuft

Find Gallons 78.5 cuft X 7.48 gal/cuft = 578.18 gallons

Find how many Gallons per Minute (578.18 gal) / (20 min) =

3. 134.64 gal/min

(15 ft X 12 ft X 3 ft X 7.48 gal/cuft) / (30 min) =