Contoured check valve disc for low cracking pressure

A contoured check valve disc features a pivot portion and a check valve portion. The check valve portion is attached to the pivot portion, and has two sides, a first side to respond to the fluid flow in a first direction and move the check valve portion away from a fluid opening to the one or more open positions depending on the fluid flow to allow the fluid to flow through the fluid opening, and a second and opposing side to respond to fluid flow in an opposite direction through the fluid opening and move the check valve portion towards the fluid opening to the closed position to seal the fluid opening and stop fluid flow. The check valve portion a near-sloped portion formed nearest to the pivot portion, having a near-sloped contoured surface curving away from the pivot point to a first point of inflection with a first curvature, and a far-sloped portion formed farthest from the pivot portion, having a far-sloped contoured surface curving away from the point of inflection towards a farthest point away from the pivot portion with a second curvature that is less curved or bent than the first curvature, the near-sloped portion and the far-sloped portion combining to form a combined surface having a contoured pressure/force distribution on the first side to respond to the fluid flow and move the check valve portion away from the fluid opening.