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The internal hydrostatic pressure acts perpendicularly on any plane with a force equal to the pressure times the area of the plane. All components of these forces acting radially within a pipe are balanced by circumferential tension in the wall of the pipe. Axial components acting on a plane perpendicular to the pipe through a straight section of the pipe are balanced internally by the force acting on each side of the plane. However, in the case of a bend, the forces acting axially along each leg of the bend are not balanced. The vector sum of these forces is the thrust force. To prevent separation of the joints, a reaction equal to and in the opposite direction of thrust force must be established. Conventional ductile iron pipe joints are push-on type joints. These joints do not offer any significant resistance to joint separation.