feet.

In

the

same

manner, the head loss is determined

a. Requirement.

Determine

the

for the 2-, 3-, and 6-inch diameter

allowable headloss Hf in the lines Al

pipes.

and A2 to provide at least 20 psi at

(1) Main AB.

Flow

=

100

gpm,

the latrine service connection and at

length = 1,400 feet.

least 30 psi at the laundry service

connection.

b. Solution.

In paragraph 16b the

allowable

headloss

was

given

as

Allowable Hf = E1Tk - (E1Sc + Hreq)

where the required head is equal to

the required pressure in psi times

2.31,

for

water.

The

allowable

headloss to each building is then

calculated as follows:

Hf Al = 200-[140' + (2.31 x 20 psi)] =

13.8'

Hf A2= 200[110'+ (2.31 x 30 psi)] =

20.7'

The allowable headloss is determined

for the service connection only, and

not points on the main.

The 2- and 3-inch pipes can be

eliminated at this point, as the

headlosses

produced

at

peak

flow

a. Requirement.

Select the pipe

exceed the maximum allowable from

sizes

and

determine

the

actual

point A to any point in the system.

headloss for the system.

Assume that

The 4-inch pipe can be eliminated as

C = 100, and that pipe is available in

the headloss from A to B is greater

2-, 3-, 4-, 6-, 8-, 10-, and 12-inch

than the maximum allowed from A to

diameter sizes.

building one.

b. Solution.

First

the

(2) Branch

B1.

The

actual

section of main from A to B will be

headloss to point B is now known for

considered.

The flow is 100 gpm; the

the size of pipe under consideration.

length 1,400 feet. From paragraph 17,

The pipe size for the branch line B1

the pipe size for the mains must be

can now be found. The total allowable

assumed.

Two, three, four, and six-

headloss from point A to building 1 was

inch pipe will be tried.

On figure

computed as 13.8 feet.

The actual

14, 100 gpm in the left column is

headloss from A to B was found to be

connected to 4 inches in the second

2.4 feet if 6-inch pipe is used. This

column.

The line is extended to

leaves 13.8 - 2.4 = 11.4 feet as the

intersect the third column as shown on

maximum that can be lost from point B

the figure.

From the intersection of

to building No. 1 if 6-inch pipe is

this

line

and

column

three,

the

used on the main AB. The length of the

headloss per 1,000 feet of pipe is

branch B1 is 400 feet. If 11.4 feet is

read as 12.5 feet.

Since the length

the largest allowable loss for 400

of

this

section

is

1,400

feet,

the

actual

headless

HfAB

is

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