Drainage control device

A drainage control device, comprising a main body, an upper cover, a lower cover, a pressure relief cover, a membrane and a return member;

• the main body having a water filling trough, a drainage trough and a water passage trough, the water filling trough and the drainage trough being in communication with the water passage trough;
• a drainage chamber being defined between the upper cover and the drainage trough, the drainage chamber having at least one drainage port;
• a water filling chamber being defined between the lower cover and the water filling trough, the water filling chamber having at least one water filling port;
• the pressure relief cover and the main body holding a periphery of the membrane;
• a water passage chamber being defined between the membrane and the water passage trough, a back-pressure chamber being defined between the membrane and the pressure relief cover, the back-pressure chamber having at least one drain port, the membrane being deformable and configured to open or close a junction of the water passage chamber and the drainage chamber as a pressure in the back-pressure chamber varies;
• the return member being disposed in the back-pressure chamber and configured to return the membrane to close the junction of the water passage chamber and the drainage chamber;
• a water supplement channel being disposed between the back-pressure chamber and the water filling chamber for the back-pressure chamber to communicate with the water filling chamber.