The engine's boiler heats water into steam, which is sent into the cylinder containing the piston. The steam pushes the piston to the top of the cylinder. The cylinder is connected to the condenser by a pipe. Because the condenser is kept cool, steam in the condenser immediately condenses into water. As steam condenses it creates a vacuum, which draws more steam into the condenser. This produces a change in pressure in the piston cylinder, which forces the piston back down. The cycle repeats as more steam from the boiler enters the piston chamber. The downward movement of the piston is used to drive machinery, such as water pumps.
