Abstract: A sluice gate assembly has a metal frame surrounding an opening and a metal gate disc mounted for movement between open and closed positions along guides on the frame. The gate disc carries a resilient deformable seal which cooperates in sealing engagement with a plastic seat face on the frame when the gate disc is in the closed position. The sealing interface between the resilient deformable seal and the plastic seat face is arranged at an angle relative to the line of travel of the gate disc along the guides, and the guides are mounted for adjustable movement towards and away from the frame seat face.