AWWA JAW59702

Pipes in distribution systems often become tubercolated, which can lead to an increase in the roughness of the pipe wall and in a reduction of the pipe diameter. Many model calibrations allow for adjusting the roughness coefficients alone, often neglecting the reduction in pipe diameter. Such oversights can have a significant effect on the prediction of correct flow velocity. This article explores the relationship between pipe roughness and effective pipe diameter. On the basis of a series of fieldwork measurements and a modeling study, the authors make several conclusions, including: calibrating models using changes in pipe wall roughness to describe measured pressure data may be insufficient to accurately model the performance of the system; and, ignoring the reduced effective diameter of the pipe can lead to incorrect predictions of hydraulic capacity. Includes 11 references, figures.