CHAPTER 1
GENERAL
those requiring supplies of cooling water, experi-
1-1. Purpose
ence greater evaporation on hot days, thus requir-
This manual provides design criteria for water
ing more water. The water treatment plant can
storage requirements at military facilities, gives a
operate at a relatively uniform rate throughout
typical design analysis for tanks and reservoirs,
the day of maximum demand if enough storage is
and provides guidance on the procedures to be fol-
available to handle variations in water use. The
lowed in selecting sites for such storage works.
necessary storage can be provided in elevated,
The manual covers requirements for treated water
ground, or a combination of both types of storage.
storage in the distribution system, but not the
d. Distribution system pressures.
storage requirements for raw water supplies or
fire deluge systems. This manual is applicable to
(1) System pressure requirements.
all elements of the Army and Air Force planning
(a) Minimum pressures. Water distribution
and designing water storage facilities at fixed in-
system, including pumping facilities and storage
stallations.
tanks or reservoirs, should be designed so that
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water pressures of at least 40 lb/in at ground
1-2. Objectives of Storage
level will be maintained at all points in the
a. Flow requirements. Storage should meet peak
system, including the highest ground elevations in
flow requirements, equalize system pressures, and
2
the service area. Minimum pressures of 30 lb/in ,
provide emergency water supply. The water supply
under peak domestic flow conditions, can be toler-
system must provide flows of water sufficient in
ated in small areas as long as all peak flow re-
quantity to meet all points of demand in the distri-
quirements can be satisfied. During firefighting
bution system. To do so, the source must produce
flows, water pressures should not fall below 20 lb/
the required quantity and quality, pressure levels
in2 at the hydrants, in new systems. This require-
within the distribution system must be high
ment does not constitute justification for changing
enough to provide suitable pressure, and water dis-
existing storage facilities solely for the purpose of
tribution mains must be large enough to carry
increasing residual pressures to 20 psi. Refer to
these flows. It is usually inefficient and uneco-
TM 5-813-6/AFM 88-10, Vol. 6 for additional
nomical to construct the treatment plant and
guidance on minimum residual pressures for fire
pumping stations sufficiently large to meet the
flow.
largest anticipated water demands. A water treat-
(b) Maximum pressure. Maximum water
ment plant is less efficient if flow rates through
pressures in distribution mains and service lines
the plant are rapidly varied. Water storage facili-
2
should not normally exceed 75 lb/in at ground
ties are constructed within a distribution network
2
elevation. Static pressures up to 100 lb/in can be
to meet the peak flow requirements exerted on the
tolerated in distribution systems in small, low-
system and to provide emergency storage.
lying areas. Higher pressures require pressure re-
b. Cost. At times it is desirable to know the cost
ducing valves on feeder mains or individual serv-
of constructing water storage for fire protection. In
ice lines to restrict maximum service pressures to
such cases only the actual fire flow for the fire
75 lb/in2.
period will be used in establishing the proportion-
(c) Multiple pressure levels. If an extensive
ate share of the total cost of storage. Cost of that
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area has pressures higher than 75 lb/in or lower
portion of the storage required for concurrent do-
2
than 40 lb/in under a single pressure level config-
mestic, industrial, or special demands that cannot
uration, it may be appropriate to divide the system
be curtailed during the fire period will not be
into two or more separate areas, each having dif-
charged to fire protection.
ferent pressure levels. Within each level, pressures
c. Meeting peak flow requirements. Water supply
within the distribution system should range from
systems must be designed to satisfy maximum an-
40 to 75 lb/in2 at ground elevation.
ticipated water demands. The peak demands usu-
(2) Pressure distribution with elevated storage.
ally occur on hot, dry, summer days when larger
than normal amounts of water are used for water-
(a) Elevated storage within the distribution
ing lawns and washing vehicles and equipment. In
system permits distribution pumps at the treat-
ment plant to operate at uniform rates.
addition, most industrial processes, especially
1-1
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