Sanitary check valves are different to many other types of valves, for check valves work automatically and most are not controlled by a person or any external control. Accordingly, most do not have any valve handle or stem. Thus there is an important concept in check valves, it is, the cracking pressure. Cracking pressure is the minimum upstream pressure at which the valve will operate. So the check valve is designed for and can therefore be specified for a specific cracking pressure. There are various types of check valves used in a wide variety of applications. Although they are available in a wide range of sizes and costs, check valves generally are very small, simple, and/or cheap.