Circular Flap Gates - Series 60
The Fontaine SERIES 60 Circular Flap Gate is designed to allow, regardless of its size, a small flow to open the gate while it will remain watertight under positive pressure.
Link to the PDF
Link to the spec sheet
Link to the video
Flap Gates up to 24 inches (610 mm) s60_1a24in.zip
Flap Gates 30 inches (762 mm) and over s60_30inp.zip