Development of system head curves is arelatively straightforward process for pumpingsystems that have a tank on both thesuction and discharge side of the pump.However, because the current hydraulicmodels work on the basic premise thatdemands are fixed, such methods for creatingsystem head curves do not produce accurateresults for complex, closed systems withno discharge-side tank. In this article, theauthors introduce a method developed torectify this shortcoming.The model described in this article works byaccurately capturing the relationship of pressureversus demand at water consumers' taps. Engineersand operators can use this model in selectingnew pumps and identifying inefficiencies inexisting pump operations. Comparisons of headcurves for systems with and without discharge-sidetanks indicated that head curves weresteeper and exhibited wider variation for systemswith no discharge-side tank, a factor that shouldbe taken into consideration in both pump selectionand setup of operational controls.Includes 9 references, figures.