Welcome to your Water Math Exam

1
**How many feet of head would create a pressure of 130 psi?**

Hint(psi x 2.31 = feet of head) 130 psi x 2.31 ft/psi

2
**What would the psi at an outlet at elevation of 419 ****ft****?**

Hint419 ft divided by 2.31 =

3
**Pump runs 18 hours and pumps 120,000 gallons what is ****gpm**** pumping rate?**

Hint18 hours x 60 min = 1080 minutes then 120,000 gallons divided by 1080 min =

4
**How much would 150 gallons of water weigh?**

HintFormula: gal. X 8.34 = lbs. of water 150 gal x 8.34 lbs./gal =

6
**How much force on 6" blind flange with 65 psi?**

Hint.785 x 6 in x 6 in x 0.785 = 28.26 sq-inches 28.26 sq-inches x 65 psi =

7
**What would be the maximum pumping rate of a 30 ****hp**** pump with 100 ****ft**** of head?**

Hint100 ft of head x ? gpm divided by 3960 = 30 hp then 3960 x 30 hp divided by 100 head ft =

8
**City spends $166,000 per year and sells 750 MG, what is cost per 1,000 gallons?**

Hint750 MG x 1,000,000 = 750,000,000 gallons (otherwise you calculator thinks its 750) 750,000,000 divided by 1000 = 750,000 gallons then $166,000 divided by 750,000 =

9
**How many gallons in an 80 ****ft**** diameter tank filled 20 ****ft****?**

Hint.785 x 80 ft x 80 ft x 20 ft = 100,480 ft3 x 7.48 gal/ft3 =

10
**How many gallons of water in an 18 inch pipe that is 5,500 ****ft**** long?**

Hint18 inches divided by 12 inches (12 in/1 ft) = 1.5 ft then .785 x 1.5 ft x 1.5 ft x = 1.766 sqft x 5500 ft = 9,714 cubic ft then 9,714 cuft x 7.48 gal/cuft =

11
**How long will a 10,000 gallon tank flow at 250 ****gpm****?**

Hint10,000 gal divided by 250 gal/min = Yes that easy

12
**How many gallons in a rectangular tank 5 ****ft**** x 8 ****ft**** x 5 ****ft****?**

Hint5 ft x 8 ft x 5 ft = 200 cuft 200 cuft x 7.48 gal/cuft =

13
**How many hours would it take to fill a 90 ****ft**** dia. tank 40 feet high pumping 2,400 ****gpm****?**

Hint.785 x 90 ft x 90 ft x 40 ft x 7.48 gal/cuft = 1,902,460 gallons then divide by 2,400 gal/min = 792.7 min now divide by 60 min/hr = 13.21 hours (Not done) .21 hours x 60 min/hr = 12.6 or 13 rounded. Final answer:

14
**How many pounds of 65% HTH would be needed to dose 300,000 gal. at 250 mg/L?**

Hint300,000 gal divided by 1,000,000 = 0.3 mg x 250 mg/l x 8.34 = 625.5 lbs (if mgd then = lbs/day) divided by .65 (or 65%) = 962 lbs So think about it, if not 100% and its weaker you will need to use more.

15
**How many pounds of 65% HTH would be needed to dose 3,500 ****ft**** of 12 inch pipe to 50 mg/L?**

HintConvert inches-feet 12 inches divided by 12 inches = 1 ft then .785 x 1 ft x 1 ft x 3500 ft x 7.48 gal/cuft = ? divided by 1,000,000 = 0.021 mg x 50 mg/l x 8.34 lbs/gal = 8.757 lbs divided by .65 = 13.5 lbs, Nap time. If you want gallons divide 13.5 by 8.34 lbs/gal =

16
**What would be the cost per day to chlorinate 4 MG at 1.5 mg/L if chlorine cost 20 cents per pound?**

Hint4 MGD x 1.5 mg/L x 8.34 lbs/gal = 50.04 lbs 50.04 lbs. x $0.20 per lbs. =

17
**A leak of 1 pint every 1.5 min. would leak how many gallons in 30 days?**

Hint1 pint divided by 1.5 min = .667 pints/min now convert min to day .667 pints/min x 1440 min/day x 30 days = 28814.4 pints, there are 8 pints in a gallon so 28814.4 pints divided by 8 pints/gallon = 3,602 gallons which may make this a hard leak to find. Gallons per day would be 3602 divided by 30 days....

18
**What is the pumping rate in ****gpm**** if the pump drains 2'**** out of a 25'**** x 35'**** basin in 1 hr.?**

Hint2 ft x 25 ft x 35 ft x 7.48 gal/cuft = 13,090 gal now divide by 60 min =