This class 125 Apollo 161S-LF series swing check valve is a lead-free y-pattern check valve, and can be installed in both horizontal and vertical line with upward flow. The valve body and seat are made of bronze for higher resistance to corrosion than brass, and are resistant to dezincification. It has solder connections on both ends for a strong and durable heat-joined bond using solder and a torch. The maximum cold working pressure (CWP) is 200 pounds per square inch (psi) at 100 degrees Fahrenheit. The working temperature range is -20 to 406 degrees Fahrenheit. This valve meets standards Manufacturers Standardization Society (MSS) SP139, National Sanitation Foundation (NSF)/American National Standards Institute (ANSI) 61-8 Annex F and G, and American Society of Mechanical Engineers (ASME) B16.18 for quality assurance.

Check valves have two ports and restrict the flow of fluids and other loose materials through a pipe or passageway to one direction. Flow enters through one port and exits through the other, closing when flow reverses or stops. Two common types of check valves are ball cone valves and swing check valves. A ball cone valve utilizes a spring-loaded ball seated against a cone-shaped interior surface to stop the flow of fluid in a forward direction, and a swing check valve has a movable disc on a hinge to block reverse flow. Check valves are rated by their cracking pressure (the minimum upstream pressure required for the valve to operate), and they are used in various water, gas, air, and steam lines.

Apollo manufactures ball, mixing, and relief valves, actuators, water gauges, marine fittings, heating and plumbing products, and backflow prevention devices. The company, founded in 1928 and headquartered in Matthews, NC, meets International Organization for Standardization ISO/IEC 17025:2005 and makes products that meet ISO and American National Standards Institute (ANSI) standards.