FRP flap gates, also known as composite flap gates, are primarily composed of unsaturated polyester resin and glass fiber. These flap gates are a type of one-way valve installed at the outlet of drainage pipes along rivers. When the river level is higher than the outlet pipe and the pressure exceeds the internal pipe pressure, the flap gate panel automatically closes to prevent river water from reversing into the drainage pipe. They are suitable for overflow and backflow prevention in various pipelines and water channels in water supply, drainage, and wastewater treatment projects, and are used for outlets in one-way water flow.