American Society of Civil Engineers


Sizing Municipal Storage Tanks Based on Reliability Criteria


by Jakobus E. van Zyl, M.ASCE, (Rand Water Chair in Water Utilisation, Dept. of Civ. Engrg. Sci., Univ. of Johannesburg, PO Box 524, Auckland Park, 2006, South Africa. E-mail: kobusvz@uj.ac.za), Olivier Piller, (Res. Scientis, Hydr. and Civ. Engrg. Res. Unit, Cemagref, 50 avenue de Verdun, Gazinet, F-33612 Cestas cedex, France. E-mail: olivier.piller@bordeaux.cemagref.fr), and Yves le Gat, (Civ. Engr., Hydr. and Civ. Engrg. Res. Unit, Cemagref, 50 avenue de Verdun, Gazinet, F-33612 Cestas cedex, France. E-mail: yves.legat@bordeaux.cemagref.fr)

Journal of Water Resources Planning and Management, Vol. 134, No. 6, November/December 2008, pp. 548-555, (doi:  http://dx.doi.org/10.1061/(ASCE)0733-9496(2008)134:6(548))

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Document type: Journal Paper
Abstract: Municipal storage tanks are used to balance differences in supply and demand. Tanks have traditionally been sized based on deterministic criteria for balancing, fire, and emergency storage components. In this paper a stochastic analysis method is proposed to model both the deterministic and probabilistic components of consumer demand, fire demand, and pipe failures in water distribution systems. The method estimates a number of tank reliability criteria as functions of tank capacity, which provide a site-specific way of determining the required tank capacity based on user-defined reliability criteria. The method is illustrated by applying it to a .typical. water supply system. It was found that the tank failure duration follows a Weibull distribution. The tank failure rate was found to be very sensitive to tank capacity and can be described with an exponential distribution. It is proposed that one failure in 10 years under seasonal peak conditions is used as a design criterion for tank sizing. In many cases this will result in substantially smaller tanks than is currently specified by design guidelines.


ASCE Subject Headings:
Water distribution systems
Storage tanks
System reliability
Stochastic models
Design
Municipal engineering