The definition of a PICV (Pressure Independent Control Valve) is a type of valve that is used to control the flow of water in a hydronic system. It is designed to maintain a constant flow rate, regardless of the pressure of the system. This is done by using a combination of a valve and a pressure regulator. The valve is used to control the flow rate, while the pressure regulator ensures that the pressure of the system remains constant. PICVs are commonly used in commercial and industrial applications, such as cooling and heating systems, and can be used to reduce energy costs. They are also used in residential applications, such as in hot water systems, to provide a consistent flow rate. PICVs are a great way to ensure that your system is running efficiently and safely.