TABLE OF CONTENTS Kenneth J. Williamson
Water distribution systems involve a water source, a transmission line, a distribution network, pumping, and storage.
The importance of the water source is primarily related to water elevation and water quality. The water elevation will determine the pumping required to maintain adequate flows in the network.
Water quality is largely determined by the source. Typical water sources include reservoirs, lakes, rivers, and underground aquifers. Surface water sources typically have low dissolved solids, but high suspended solids. As a result, treatment of such sources requires coagulation followed by sedimentation and filtration to remove suspended solids. Groundwater sources are low in suspended solids, but may be high in dissolved solids and reduced compounds. Groundwater, if high in dissolved solids, requires chemical precipitation or ion exchange for removal of dissolved ions.
A transmission line is required to convey water from the sources and storage to the distribution the system. Arterial main lines supply water to the various loops in the distribution system. The main lines are arranged in loops or in parallel to allow for repairs. Such lines are designed using the Hazen-Williams formula for single pipes (Eq. 7-1) and the equivalent pipe method for single loops. Multiple loops are designed using Hardy Cross methodology.
| (7-1) |  |
where:
| v | = | pipe velocity (m/s), |
| k | = | constant (2.79), |
| C | = | roughness coefficient (100 for cast iron pipe), |
| r | = | hydraulic radius (m), and |
| s | = | slope of hydraulic grade line (m/m). |
The equivalent pipe method involves two procedures:...
