Civil Engineering Reference
In-Depth Information
CHAPTER 28
Distribution Systems
INTRODUCTION
A water distribution system conveys water from the treatment facilities to the user.
The distribution system should supply water, without impairing its quality, in adequate
quantities and at sufficient pressures to meet system requirements.
The facilities that make up the distribution system include finished water storage,
pumping, large-scale transmission and distribution piping, supply mains, and appur-
tenant valves. This chapter will discuss the distribution system components not covered
in other chapters, the basis for their sizing and design, considerations for construction
and maintenance, and techniques to evaluate the impacts of water demands on existing
systems. Storage facilities are discussed in Chapter 27, and pumping systems in Chap-
ter 29. Water system planning is discussed in Chapter 7.
The water distribution system must be capable of supplying water needed for basic
domestic purposes and commercial and industrial uses, and where possible, the flows
necessary for fire protection. The safety and palatability of potable water should not
be degraded as it flows through the distribution system (refer to Chapter 22).
SYSTEM CAPACITY
Distribution system design or analysis is based on peak hour demands or fire flow
demand, while other system demands are something less than peak hour. Computerized
analysis permits running simulated extended periods of water demand and system
storage replenishment. Acquiring the basic data to calibrate the model and identify
detailed variable system demands may be a straightforward procedure or it may be
difficult, depending on the existence and type of records available. More likely, the
engineer will be required to apply empirical ratios to simulate peak demands and
demand variations.
In most water systems there are a variety of customer classes and system needs.
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Water use and demand will vary, depending on customer class. Customer classes may
be broken down into residential and commercial / industrial, or may be more finely
divided into single-family residential, multifamily residential, parks, schools, heavy
industrial, light industrial, commercial, and so forth. The finer the breakdown and the
more accurate the data, the better the determination of demand requirements.
Once the various system demands are determined, it is then possible to analyze the
water distribution system.
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