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ISAWWA WATER DISTRIBUTION CONFERENCE

APRIL 28TH , 2015

Basic Math Conversions

1ft3 = 7.48 gallons

1gallon = 8.34 lbs

1mg/l = 1ppm

1% = 10,000 mg/l

1psi= 2.31ft of water

1 in of mercury = 1.13 ft of water

1day = 1440 mins

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Basic Math Formulas

A= 3.14 R2 or A= .785 (D2) ( AREA OF A CIRCLE)

V= A X H ( VOLUME OF A RECTANGULAR TANK)

Q= VA ( VELOCITY FORMULA)

MG x mg/l x 8.34 = lbs ( POUNDS FORMULA)

QS CS = QW CW ( SOLUTIONS FORMULA)

TREATED WATER – BILLED WATER / TREATED WATER = ( UNACCOUNTED FOR WATER)

PUMPING LEVEL – STATIC LEVEL = ( DRAWDOWN)

GPM / DRAWDOWN = ( SPECIFIC CAPACITY)

CHLORINATION MATHThe Pounds Formula

QsCs = QwCw

Feed Rates

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The Pounds Formula lbs = MG x mg/L x 8.34

where

lbs = lbs of chemical

MG = volume of water in million gallons

8.34 = the factor converting mg/L to lbs.

Example 1. How many pounds of chlorine are needed to provide a 50 mg/L chlorine dosage in a 500,000 gallon storage tank?

lbsLmgMGlbs 5.20834.8/505.0

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Example 2. How many pounds of HTH (Calcium hypochlorite - 70% chlorine) are needed to provide a 50 mg/L chlorine dosage in a 500,000 gallon storage tank?

lbslb

LmgMGlbs 29870.

5.20834.8/505.0

Example 3. How many pounds of chlorine are contained in 209 lb of 70% HTH?

209 lb HTH x .70 = 146.3 lb chlorine

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QsCs = QwCwThe Solution Mixing Formula where:

Q is quantity

C is concentration

"s" is strong

"w" is weak.

How much 15 % NaOCl needs to be fed to a 1 MGD rate of flow for a 10 mg/L chlorine dosage? In other words, what will Qs be?

Qs = ? gallons

Cs = 150,000 mg/L

Qw = 1,000,000 gallons

Cw = 10 mg/L

Note that the units are the same now for Qs and Qw (gallons), and for Cs and Cw (mg/L).

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Do the Math …. Solve for Qs. (Qs) (Cs) = (Qw) (Cw)

(Qs)(150,000 mg/L) =(1,000,000 gal)(10 mg/L)

Qs = (1,000,000 gal) ( 10 mg/L)

150,000 mg/L

Qs = 66.7 gallons of 15 % NaOCl

Feed Rates: From the previous example, the 66.7

gal of 15% NaOCl is fed over 24 hours. What is the feed rate?

66.7 gallons = 2.78 gallons x 1 hour

24 hours 1 hour 60 min

= .0463 gpm

= .0463 gal x 3785 ml = 175 ml

min gal min

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UNACCOUNTED FOR WATER

The chief operator is presenting the annual report

To his city council as follows:

Raw Water Pumpage is 177,025,000 gallons

Treated Water Pumpage is 174,370,000 gallons

Billed Water ( Metered Water ) is 153,445,300 gallons

What is the percent of unaccounted for water ?

Do the math …..

Treated water Pumpage 174,370,000

Billed Water ( Metered water ) - 153,445,300

equals 20,924,700

20,924,770

174,370,000 = .12 or 12%

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Velocity of water

How many MGD can be delivered by a 12” DI water main if the velocity is 3.5 feet per second?

Do the math …..

Q= V * A

Q= .785 x 1 x 1 x 3.5 ft = 2.7475

sec

Q= 2.7475 x 7.48 x 60 sec = 1233 gpm

sec 1ft 3 min

Q= 1233 gpm x 1440 min = 1.78 MGD

1 day

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Drawdown

An air line is 80 feet long. After pumping it with air. The air line reads 20 psi. What is the static level?

20 psi x 2.31 = 46 feet.

80 feet – 46 feet = 34 feet ( static level)

The well pump is turned on and runs for two hours. The air line pressure gauge reads 10 psi. What is the pumping level?

10 psi x 2.31 = 23 feet

80 feet – 23 feet = 57 feet ( Pumping level)

Do the math …..

Drawdown = Pumping Level – Static Level

57 feet ( Pumping Level) – 34 feet ( Static Level)=

23 Feet ( Drawdown)

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Specific Capacity

Specific Capacity is = GPM

FEET OF DRAWDOWN

If the pumping flow from the previous problem was 460 gpm then the Specific Capacity will be as follows:

460 gpm

23 feet of Drawdown = 20

ANY QUESTIONS?