A series of computer programs has been developed to assist in the optimal design of pipe distribution networks. These programs are capable of handling nonstandard network components such as booster pumps, minor-loss devices, reservoirs, check valves, and pressure-reducing valves. All three stages of network problem, namely analysis, design, and optimization, can be solved using the same solution procedure. A known technique for layout design has been adapted to help in the selection of redundant links.The problem is formulated as a nonlinear program using as design variables the diameter, discharge, and shutoff head (where appropriate) for each link. Pump lift is assumed to be described by a parabolic Q–hp curve, the coefficients of which may be defined by the user. A powerful, large-scale, nonlinear, sparse-oriented package (MINOS) is used to solve the problem. The continuous solution obtained by MINOS is modified by a discretization procedure to arrive at the optimal discrete solution. The constraint matrix including the loop, nodal head, and continuity constraints is automatically generated.The user is required to supply a simple and concise data file that will be interfaced by a preprocessor to generate the large and complicated data file required by MINOS. The latter data file includes the nonzero elements of the constraint matrix, ordered and stored in a column-by-column fashion. A postprocessor is also used to convert the mathematical output of the package into easily understood engineering data. Three different network examples are used to demonstrate the different aspects of the model (i.e. nonstandard components, discretization procedure, and layout design). Key words: networks, optimization, design, distribution, water supply, nonlinear.