A water purification device (30) is provided for installation in an aircraft potable water system. The device (30) comprises a treatment cell (40) incorporated into the water system's plumbing and a flashlamp (50) positioned to productively transmit into the treatment chamber (41) of the cell (40). The flashlamp (50) emits short-pulse and high-intensity flashes, thereby delivering adequate UV doses (e.g., at least 40 mJ/cm2) with reasonable input power (e.g., 400 watts) for an aircraft system.