A backwater valve has a hollow valve body with an inlet and an outlet and a valve member pivotally movable about a pivot axis disposed above the inlet. The valve member is movable between a closed position covering the inlet and an open position. The valve member has a specific gravity that is greater than water and has a basin that causes the valve member to be buoyant when the basin is filled with air. A releasable latch holds the valve member in the open position and releases the valve member when the valve member pivots to a release position. A rotational stop engages the valve member at a fill position permitting water to overflow into the basin.