In PEM fuel cells, electro-osmotic drag (EOD) and back diffusion (BD) are two well-known drivers of water transport across the membrane. Thermal osmosis (TO) is less understood, so much so that the available research is unclear that there are two types of TO that can occur: single-phase and two-phase (called membrane distillation (MD) in prior research). Which occurs depends upon the phase of the fluid on either side as well as the type of membrane. Hybrid membranes such as those used in PEM fuel cells to support EOD and BD contain both hydrophobic and hydrophilic regions and can give rise to both modes of TO simultaneously. Most available experimental research efforts used either hydrophobic or hydrophilic membranes and very few used hybrid membranes. In hydrophobic membrane experimental results where the liquid phase is present, two-phase TO (MD) may occur. If there was not an awareness of the possibility of this less-understood mode of transport, then this could easily be mistaken as EOD and/or BD in the results. In experiments containing EOD, BD and TO, there are difficulties in measuring the magnitude of each driver since only the net water flow is measured. The current research examines the difference between single and two-phase TO as well as a method to isolate component drivers of the net water flow. As shown in this paper, it is likely that some former research results, unaware of the possibility of MD, may have attributed multiple mechanisms to single drivers.