The Water & steam tool is used to calculate the properties of water and steam. These values are calculated using "The International Association for the Properties of Water and Steam, Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam." Entropy and enthalpy, for a fluid stage, are calculated using Equation 7, and for a vapour stage using Equation 15, 18 and 19, both as a function of pressure and temperature. Finally, the saturation temperature is calculated using Equation 31 as a function of pressure.