Long-term Water Distribution Design

Water distribution piping has a useful life on the order of a century while pipe-sizing decisions are usually based on a planning horizon on the order of 20 years. Because of the substantial economy of scale in pipe sizing and the long useful life, there may be benefits to installing piping with some excess capacity in the short term depending on expected long-term growth. The analysis presented in this paper shows the value in considering long-term growth in demand even if the planning horizon for the study is much shorter. While the only decision that needs to be made in the current year is the size of the initial pipe, it is important that the pipe fits into a long-term plan for the distribution system but the exact diameter doesn't make much difference.