CEMP-E
TI 814-01
3 August 1998
CHAPTER 3
CAPACITY OF WATER-SUPPLY SYSTEM
3-1. CAPACITY FACTORS. Capacity factors, as a function of "Effective Population" are
shown in table 3-1, as follows:
Table 3-1. Capacity Factors.
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Effective Population
Capacity Factor
5,000 or less
1.50
10,000
1.25
20,000
1.15
30,000
1.10
40,000
1.05
50,000 or more
1.00
3-2. USE OF CAPACITY FACTOR. The "Capacity Factor" will be used in planning water
supplies for all projects, including general hospitals. The proper "Capacity Factor" as given in
table 3-1 is multiplied by the "Effective Population" to obtain the "Design Population."
Arithmetic interpolation should be used to determine the appropriate Capacity Factor for
intermediate project population. (For example, for an "Effective Population" of 7,200 in
interpolation, obtain a "Capacity Factor" of 1.39.) Capacity factors will be applied in
determining the required capacity of the supply works, supply lines, treatment works, principal
feeder mains and storage reservoirs. Capacity factors will NOT be used for hotels and similar
structures that are acquired or rented for hospital and troop housing. Capacity factors will NOT
be applied to fire flows, irrigation requirements, or industrial demands.
3-3. SYSTEM DESIGN CAPACITY. The design of elements of the water supply system,
except as noted in paragraph 3-2, should be based on the "Design Population."
3-4. SPECIAL DESIGN CAPACITY. Where special demands for water exist, such as those
resulting from unusual fire fighting requirements, irrigation, industrial processes and cooling
water usage, consideration must be given to these special demands in determining the design
capacity of the water supply system.
3-5. EXPANSION OF EXISTING SYSTEMS. Few, if any, entirely new water supply systems
will be constructed. Generally, the project will involve upgrading and/or expansion of existing
systems. Where existing systems are adequate to supply existing demands, plus the
expansion proposed without inclusion of the Capacity Factor, no additional facilities will be
provided except necessary extension of water mains. In designing main extensions,
3-1
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