Cast iron butterfly valves are designed for circular and square outlets for one-way water flow. They feature a tight structure and reliable operation, requiring no manual operation. The opening and closing force is derived from the water pressure source. The valve opens when the water pressure inside the cast iron butterfly valve exceeds the external pressure, and closes otherwise. The butterfly valve consists of four parts: valve seat, valve plate, sealing ring, and hinge. It is suitable for hydraulic systems, municipal sewage, urban flood prevention and drainage, wastewater treatment plants, waterworks, and more. The specifications include circular and square butterfly valves, which can be designed and manufactured according to the size and shape of the outlet.