Rubber flap check valve and swing check valve are two common types of check valves, which have significant differences in structure, working principle, performance characteristics, and application scenarios.

Core structure and working principle
Rubber flap check valve:
Structure: The core component is a one-piece rubber valve (usually made of rubber or elastic material, with a metal or plastic skeleton reinforcement inside). This valve is usually shaped like a duckbill or umbrella, covering the inlet of the valve body.
Working principle: When the fluid flows forward, pressure acts on the inside of the valve, causing it to elastically deform and open outward, allowing the fluid to pass through. When the fluid stops flowing or flows in the opposite direction, the valve relies on its own elastic recovery force (sometimes combined with the slight pressure of the reverse fluid) to automatically rebound and close, tightly fitting on the valve seat to prevent backflow. Similar to the principle of "duckbill" opening and closing.
Swing check valve:
Structure: The core component is a metal (or hard plastic) valve disc (disc-shaped or similar shape), which is mounted inside the valve body through hinge pins or pivot shafts.
Working principle: When the fluid flows forward, the fluid pressure pushes the valve disc to rotate upwards (or sideways) around its pivot and open, like a door being pushed open. When the fluid stops flowing or flows in the opposite direction, the valve disc relies on gravity (or sometimes equipped with counterweights or spring assistance) to rotate downwards (or backwards) around the pivot, closing and covering the valve seat to prevent backflow. Its movement is a process of rotation and swinging.

Typical application scenarios
Rubber flap check valve:
Building water supply and drainage system (especially anti backflow at pump outlet).
Municipal and industrial sewage treatment system (sewage pump outlet, aeration tank, sewer discharge outlet).
Rainwater drainage system.
Fluid pipelines containing impurities such as fibers, sediment, and particles.
Low pressure air system.
In situations where low flow resistance, quick closing, and anti blocking are required.
In situations where installation space is limited or vertical installation is required.
Swing check valve:
Water, steam, oil, and gas transportation in industrial pipeline systems.
Boiler feedwater system.
Cooling water system.
High pressure water pump outlet (under the condition of allowing a certain amount of water hammer).
Clean or low impurity chemical processes.
In situations where it is necessary to withstand medium to high pressure and high temperature.
Large diameter pipeline system (whose structure makes it easier to achieve large diameter).