TABLE OF CONTENTS Thomas M.Walski
Pennsylvania American Water Company
Wilkes-Barre, PA
Water storage tanks are a commonly used facility in virtually all water distribution systems. Methods for sizing and locating these facilities to provide equalization and emergency storage have changed little over the years. Recent years, however, have seen an increased awareness of water-quality changes that can occur in storage tanks. Because water-quality problems are usually worse in tanks with little turnover, no longer it is safe to assume that a bigger tank is a better tank. There is increased emphasis on constructing the right-sized tank in the right location.
Water-quality concerns will not radically change tank design, but they do call for a reassessment of some design practices, This chapter summarizes the state-of-the-art in tank design.
Water distribution storage is provided to ensure the reliability of supply, maintain pressure, equalize pumping and treatment rates, reduce the size of transmission mains, and improve operational flexibility and efficiency. Numerous decisions must be made in the design of a storage tank, including size, location, type, and expected operation. This chapter focuses on the hydraulic aspects of design as opposed to structural, corrosion, safety, contamination, or instrumentation aspects. (In this chapter, the word tanks will be used to describe treated water-storage facilities, although the term reservoirs is preferred by some, whereas others use the word reservoir to describe only ground-level and buried tanks.)
The key considerations in the hydraulic design of water storage tanks are described in the following sections...
