www.pmmag.com/articles/92288-double-check-valves
Double Check Valves
October 28, 2008

The new DC 4A Series double checks from Apollo Valves employ unique “captured spring” check modules that allow for a more compact design that fits in standard meter boxes or under smaller enclosures. The valves include two self-contained check modules that are independently accessible from the top, which are easily removable and can be replaced or disassembled for standard maintenance.