Typically, pump manufacturers use water to obtain the values for their pump performance curves, even if the intended service of the pump is for a fluid with properties that are different from water. For example, a fluid with high viscosity, such as maple syrup, is thicker and resists flow more when compared to a fluid with a lower viscosity, like water. It is a fluid’s resistance to flow and is higher for thicker fluids.
Viscosity is a fundamental property of a liquid.
