Wave-driven reverse osmosis desalination systems can be a cost-effective option for providing a safe and reliable source of drinking water for large coastal communities. Such systems usually require the stabilization of pulsating pressures for desalination purposes. The key challenge is to convert a fluctuating pressure flow into a constant pressure flow. To address this task, stub-filters, accumulators, and radially elastic-pipes are considered for smoothing the pressure fluctuations in the flow. An analytical model for fluidic capacitance of accumulators and elastic pipes are derived and verified. Commercially available accumulators in combination with essentially rigid (and low cost) piping are found to be a cost-effective solution for this application, and a model for selecting accumulators with the required fluidic-capacitance for the intended system is thus presented.