Water System Design Manual
Power connections are available to two independent primary public power sources, or
there is a provision for in-place auxiliary power if the pumps provide fire flow or are
pumping from ground-level storage.
Distribution Storage (refer to Chapters 5 and 9)
More than one gravity storage tank (wherever feasible) exists with the ability to isolate
each tank while continuing to provide service.
Storage is sufficient to give standby capacity of at least two times the ADD for all users,
and to ensure that fire suppression service will be available while not allowing pressure to
drop below 20 psi at any service connection.
A minimum standby volume of 200 gpd per residential connection, or equivalent, is
provided regardless of the capacity of the sources available.
An alarm system is included that notifies the operator(s) of overflows, or when the
storage level drops below the point where the equalizing storage volume is depleted. This
should only occur during abnormal operating conditions.
Distribution System (refer to Chapter 8)
Distribution mains are looped wherever feasible.
Pipeline velocities do not exceed eight feet per second under PHD conditions.
All pipelines can be flushed at a flow velocity of at least 2.5 feet per second.
All mains and distribution lines have appropriate internal and external corrosion
If fire flow is provided, the engineer should conduct a hydraulic analysis to determine
whether high firefighting demands may cause very low pressure (below 30 psi) in the
distribution system. Very low water system pressure presents an increased risk of
contamination from cross-connections and pathogen intrusion at joints.
American Association for Vocational Instructional Materials. 1982. Planning for an Individual
Water System, 4
Edition, American Association for Vocational Instructional Materials,
AWWA. 1984. Design and Construction of Small Water Systems, American Water Works
Association, Denver, CO.
AWWA. 1999. Water Meters Selection, Installation, Testing, and Maintenance. AWWA
Manual M6. American Water Works Association, Denver, CO.
AWWA. 2004. Computer Modeling of Water Distribution Systems, 2
Edition. AWWA Manual
M32. American Water Works Association, Denver, CO.