TABLE OF CONTENTS In some less-developed countries, providing water service on a part-time basis may be acceptable, but customers in developed countries expect an uninterrupted supply of water. This expectation of uninterrupted water increases the cost of the water distribution system and has an impact on the design, operation, and maintenance of water systems. Section 18.2.2 describes some facets of improving the reliability of water distribution (Walski, 1993a). These include a range of design considerations ranging from specification of adequate pipe material to use of transient analysis. Valving of the system into distribution segments is addressed in the following section. (A segment is the smallest portion of a distribution system that can be isolated by valving.)
The selection of pipe material can be complicated by the large number of materials available and the complexity of conditions at local sites. The key is to match the material with the laying condition and internal and external loads. With proper design, most pipe material will work in most conditions and the cost, including ease of maintenance and historical recording of the performance of that material in that utility, will determine the selection.
Bedding is the next consideration, and compliance with the manufacturer s directions usually will result in acceptable laying conditions. Depending on the soil type, it is usually justifiable to coat or wrap metal piping. Refer to Chap. 3 for further discussion of bedding.
Specifying the pressure rating of...
