Section IV. WATER DISTRIBUTION SYSTEMS
Water distribution is the process of getting water from the point of treatment to
the place where it is to be used by the consumer. In a municipal or garrison system,
this involves two important functions--carrying potable water for domestic use and
concentrating high rates of flow for fire fighting purposes. In a field distribution system,
the provision of water for fire fighting purposes is not included since such a mission
would overtax our field water distribution capabiIities. In both garrison and field water
distribution systems, purity is a paramount consideration. No matter how completely
and carefully the potable water supply is treated, all efforts are wasted, and the health of
the command is endangered if drinking water is permitted to become contaminated.
1-19. GARRISON WATER DISTRI8UTION SYSTEMS
a. Types of Systems. In a garrison or municipal water distribution system,
water is distributed to the consumer by anyone or a combination of the following
(1) Gravity. Where the source of supply is a lake or impounding reservoir,
which is located at an elevation higher than that of the community being served, water
may be distributed by gravity. This is the most reliable system, if the conduit from the
source to the community is of adequate size and is well protected against accidental
breaks. The principal advantage of this system is its simplicity since gravity maintains a
uniform pressure (head) within the system without the use of pumps. High pressure for
fire fighting, however, requires the use of pumping equipment.
(2) Pumps with storage. A very common method of water distribution is that
of combining storage tanks with pumps to maintain constant pressure. This system is
economical in that pumps may be operated at a uniform rate at or near their rated
capacity. During periods of low consumption, water is pumped into the storage tanks.
During periods of high consumption, the water in the storage tanks is then drawn upon
to augment that being pumped. The storage may be either surface or elevated storage.
In the latter, the elevation assists in maintaining pressure.
(3) Direct pressure. Some distribution systems employ pumps without
water storage faciIities. In this type of system, the pressure is maintained directly by the
pumps. Water is pumped directly into the mains with no outlets other than the water
actually consumed. The system is the least desirable because a power failure would
cause complete interruption of the water supply and because the pressure varies with
the consumption. A very hazardous situation could exist if a fire occurred during a
period of peak consumption. Additional booster pumps are required to cope with such a