Flap Gates

Flap gates are made of cast iron or ductile iron, depending on the type of service. Optional stainless steel or aluminum is also available. A small differential pressure on the back of the gate causes it to open automatically to allow discharge through levees, sewer lines or drainage conduits. When water on the face side of the gate rises above water on the back side, the gate closes automatically to prevent backflow.

Flap gates are equipped with flat-back seats for attaching to wall thimbles, new concrete headwalls, existing walls or pipe flanges. The seat or frame of the flap gate is attached to a wall or pipe flange and forms the opening through which water passes. Because the gate opens or closes automatically, a mechanical lifting device is not necessary. Automatic drainage gates must be kept clean if they are to function correctly. The hinged flap acts as a natural skimmer to cause timber, logs or trash to catch between the flap and the seat at low flow. Periodic inspection and cleaning should be scheduled when the water flowing through the flap gate carries floating material.

To make the gate more self-cleaning, it should be mounted 12" to 18" above the apron in front of the gate. This allows room at the bottom for floating material to work its way out and makes the gate flap somewhat self-cleaning. 

Typical Applications

• Flood control
• MunicipalpProjects
• Farm levees
• Sewer outfalls
• Industrial waste lines
• Water and sewage treatment plants
• Tidal drainage
• Irrigation systems
• Pump discharge control

Features

• Standard sizes 8” to 96”
• Standard designs of 10’ (10C) and up to 50’ (50C)
• Round, square or rectangular openings
• Self-contained configuration
• Available with cast iron or bronze seating faces
• Quality at a cost-effective price
• Can be mounted to a wall, flange or pipe
• Most sizes available from stock
• Cast iron gates are robust and designed to resist warping, deflection under head and damage when closing on debris
• Minimum maintenance is required
• Seating faces are machined cast iron or machined bronze for optimum sealing under low head