1. Find pumping rate of lift station if gpm.
Wet well diameter: 8 ft
Drawdown time: 315 sec Refill time: 523 sec
Drawdown distance: 2.26 ft Refill distance: 2.35 ft

2. Wet well diameter: 10 ft, Drawdown time: 5 min, 7 sec, Drawdown distance: 2 ft 4 inches, Refill time: 7 min, 23 sec, Refill distance: 2 ft 5 inches
What is the pumping rate, in gallons per minute, of a lift station pump?

3. In a lift station with a diameter of 10 feet, the water level was lowered 6 inches in 2 minutes. What is the pumping rate in gallons per minute?

Answers:

1. 263 gal/min
Pumping Rate, gpm = [(Drawdown Volume)/(Drawdown Time)] + [(Refill Volume) / (Refill Time)] Find Drawdown Volume = (draw your circle and name your parts):(8 ft diam)/(2) = 4 ft Radius
Volume = 3.14 X R, ft X R, ft X H, ft = 3.14 X 4 ft X 4 ft X 2.26 ft = 113.54 cuft
(NOTE: Height in this case is the Drawdown Distance)
(NOTE: Could have used 0.785 X D, ft X D, ft X H, ft or 0.785 X 8 ft X 8 ft X 2.26 ft)
Convert cubic feet to gallons: 113.54 cuft X 7.48 gal/cuft = 849.3 gal Drawdown Volume
Convert Drawdown Time from Seconds to Minutes = (315 sec) / (60 sec/min) = 5.25 Drawdown Time, min
Next find Refill Volume = 3.14 X 4 ft X 4 ft X 2.35 ft = 118.064 cuft
(NOTE: Could have used 0.785 X 8 ft X 8 ft X 2.35 ft)
Convert cuft to gal: 118.064 cuft X 7.48 gal/cuft = 883.19 gal
Convert Refill Time from Sec to Min = (523 sec) / (60 sec/min) = 8.72 min
Work problem, [(849.3 gal) / (5.25 min)] + [(883.91 gal) / (8.72 min)] =
(161.77 gal/min) + (101.37 gal/min)

2. 460 gal/min
Pumping Rate, gpm = [(Drawdown Volume)/(Drawdown Time)] + [(Refill Volume) / (Refill Time)] Find Drawdown Volume: (draw your circle and name your parts):(10 ft diam)/(2) = 5 ft Radius
Volume = 3.14 X R, ft X R, ft X H, ft
Inches need to be converted to feet:(4 in)/(12 in/ft)= 0.33 ft, so 2 ft + 0.33 ft = 2.33 ft
= 3.14 X 5 ft X 5 ft X 2.33 ft = 182.91 cuft
(NOTE: Height in this case is the Drawdown Distance)
(NOTE: Could have used 0.785 X D, ft X D, ft X H, ft or 0.785 X 10 ft X 10 ft X 2.33 ft)
Convert cubic feet to gallons: 182.91 cuft X 7.48 gal/cuft = 1368.13 gal Drawdown Volume
Seconds need to be converted to minutes = (7 seconds) / (60 seconds/min) = 0.11 min
So, 0.11 min + 5 min = 5.11 min
Inches need to be converted to feet:(5 in)/(12 In/ft)= 0.42 ft, so 2 ft + 0.42 ft = 2.42 ft
Next find Refill Volume = 3.14 X 5 ft X 5 ft X 2.42 ft = 189.97 cuft
(NOTE: Could have used 0.785 X 8 ft X 8 ft X 2.42 ft)
Convert cuft to gal: 189.97 cuft X 7.48 gal/cuft = 1420.98 gal
Convert Refill Time from Sec to Min = (23 sec) / (60 sec/min) = 0.38 min
So, 0.38 min + 7 min = 7.38 min
Work problem, [(1368.13 gal) / (5.11 min)] + [(1420.98 gal) / (7.38 min)] =
(267.73 gal/min) + (192.54 gal/min)

3. 147 gal/min
Formula is (gallons) / (time, minutes)
Find Volume in Cuft of wet well: 3.14 X R, ft X R, ft X H, ft
Height will be how low the water level was lowered (convert inches to feet): (6 in) / (12 in/ft) = 0.5 ft
(10 ft diam) / (2) = 5 ft Radius or 3.14 X 5 ft X 5 ft X 0.5 ft = 39.25 cuft
Convert cuft to gallons = 39.25 cuft X 7.48 gal/cuft = 293.59 gal
Work the formula: (293.59 gal) / (2 min) =