Two-phase flushing systems and methods. An example method includes moving a valve to a first position to fluidly connect a first reagent reservoir containing a first reagent to a flow cell and flowing the first reagent from the first reagent reservoir to the flow cell to perform a biochemical reaction. The method includes moving the valve to a second position to fluidly connect a gas to the flow cell and flowing gas into the flow cell to expel at least a portion of the first reagent from the biochemical reaction from the flow cell. The method includes moving the valve to a third position to fluidly connect a buffer reagent reservoir containing a buffer reagent to the flow cell and flowing the buffer reagent into the flow cell.