The cross-flow turbine is an attractive technology for small-scale hydropower generation thanks to its low capital cost and relatively high efficiency even under partial discharge operating conditions. It has been proposed that this kind of turbine can be manufactured from standard steel pipe sections given its simple geometry, an alternative that would further decrease the turbine’s capital cost compared to highly engineered cross-flow designs. This article explores the trade-offs encountered during the design of cross-flow turbines under the constrains imposed by the discrete set of dimensions available for commercial steel pipes. First, the computational model is presented, analyzed in terms of its convergence behavior, and validated with experimental data. Then, a parametric analysis is performed to understand the relative importance of the design variables and their optimum value in regard to the turbine efficiency. Based on the design guidelines derived from the parametric analysis, an example cross-flow turbine design is presented and thoroughly characterized, demonstrating that it is possible to engineer a cross-flow turbine of competitive efficiency out of commercial steel pipes. These guidelines may encourage the use of cross-flow turbines as an appropriate technology for off-grid regions.