The 600 series flanged, in-line disc-type check valves are spring closing with a light spring. They may be installed in vertical or horizontal runs. Bodies up through 2" are steel; 3" and 4" bodies are cast semi-steel. There is a removable back plate which allows the valve to be disassembled for maintenance.
The 600D has a metal to metal seat. The 60OD2 and 60OD3 check valves incorporate the Durabla check valve unit. Series 600D and, "S," suffix valves are spring loaded to close requiring about 2 psi pressure drop to open.
The series 600J and 600K valves are teflon seated valves. When ordered without the, "S," suffix they are supplied with a light spring, making them suitable for gravity drain lines.