An in-line check valve is a type of valve used in fluid systems to allow the flow of fluid in one direction while preventing backflow in the opposite direction. Similar to a lift check valve, it relies on the principle of preventing reverse flow. However, in an in-line check valve, there is generally a spring mechanism that assists in lifting the valve disc when there is sufficient pressure on the upstream side. Top manufacturers of in-line check valves include companies like Apollo Conbraco, Victaulic, Nibco and Titan Flow Control. These valves find applications in a wide range of settings, including industrial processes, water supply systems, wastewater treatment plants, and oil and gas pipelines, where maintaining a unidirectional flow and preventing backflow is critical to the efficient and safe operation of the system.