Y piston check valves have an angled disc and seat to reduce flow resistance and minimize pressure drops within the system. Maintenance and inspection can be conducted on these valves while connected to the system. These piston check valves direct system media straight through the housing without changing flow direction and prevent backflow. Pressure caused by incoming media on the inlet side raises the piston and opens the valve. When pressure on the inlet side of the valve is lower than the outlet, the piston drops into the valve seat to stop flow. These valves are suitable for low-flow applications and low-viscosity media in various industrial, manufacturing, and treatment operations.