In-Line Check Valves work as a form of Backflow Prevention in lower risk applications.  These one way valves require a higher fluid pressure on the inlet side than the outlet side to open the valve.  If the pressure is higher on the outlet side, the valve will close.

Although In-Line Check Valves are available in a wide range of sizes, these are generally very small, simple, and inexpensive. Check valves work automatically and most are not controlled by a person or any external control; nor do they have a handle or stem.  The valve is normally located on the outlet side of a pump to prevent any backflow.

Bonomi Check Valves offer Stainless Steel, Brass, and Lead Free Brass options that are spring loaded with FNPT threads.  They provide a standard low-cracking pressure of 1/2 PSI; which makes it a preferred choice in many different applications.