assure the designer there will be no

adequate pressure will be available

point

along

the

line

where

the

even when a facility is drawing its

hydraulic gradient will fall below the

maximum

flow

(peak

demand).

At

required head at the outlet.

In the

military

installations

there

are

theater of operations, construction

essentially three times each day when

lines are normally located adjacent to

the peak demand will be approached.

roadways with a minimum number of

These times are in the morning when

crossings so that repair of the lines

the troops arise and breakfast is

will not affect traffic.

prepared, at midday when troops have

returned to the barracks for the noon

meal, and in the late afternoon, at

the end of the duty day.

Unless the

For

standard

pipe,

the

maximum

population exceeds 1,000 men, the flow

pressure allowed anywhere in the line

rates in the mains and branches are

is 100 psi.

A check must be made at

found by summing the peak demands of

low points in a water line to insure

the facilities serviced by the line

that the pressure does not exceed 100

under

consideration.

If

the

psi.

If the pressure does exceed 100

population exceeds 1,000 men and there

psi, stronger pipe must be used or a

are large users, this simple addition

different layout determined.

The

of peak demands may be too high since

pressure at any point in the system

the peak demands may not occur at the

can

be

found

by

the

following

same time. In such a case, savings in

construction requirements can be made

by determining when the peaks occur

Pressure = 0.433 (E1Tk - El of point).

and using an adjusted peak demand

E1Tk is the elevation of the storage

based on engineering judgment and

tank.

experience.

El of point is the elevation of the

b. The peak demand of a facility

point in question.

depends on the number of outlets and

showers (fig 13).

(Any water fixture

For the pressure to be greater than

other than a shower is considered an

100 psi, the difference in elevation

outlet.)

If there are no showers in

must be as follows:

the facility, only the left column in

figure 13 need be used.

The peak

100 = 0.433 (E1Tk - El of point).

demand, in this case, is found on the

right side of the column opposite the

number of outlets found on the left

side.

If there are both showers and

Therefore, any pace where the line is

outlets, the peak demand is found by

more than 231 feet below the tank, the

connecting the number of outlets on

pressure, discounting friction losses,

the left column and the number of

will exceed 100 psi.

This type of

showers on the right column with a

static pressure check must be made for

straight line.

The peak demand is

every system to insure that the static

read

at

the

intersection

of

the

pressure in the line does not exceed

straight line and the center column.

the safe working pressure of the pipe.

a. Definition.

As

the

name

a. The source size and storage size

implies, allowable headloss is the

were

computed

using

the

average

maximum amount of head which may be

demand.

The

design

of

the

lost to friction between the storage

distribution system, however, is based

tank

and

the

facility

under

on the peak demand to insure that

consideration.

Thus, pipe sizes must