CL-D-NPB - 1-1/4" Piston Water Hammer Arrestor - 61 to 113 Fixture UnitsMifab CL D NPB 1 1 4" Piston Water Hammer Arrestor 61 to 113 Fixture Units Used in commercial, institutional and residential applications on water supply lines to reduce water hammer caused by the quick opening and closing of valves within the piping system. To be installed as close as possible to quick closing valves. The resulting hydraulic shock waves can lead to broken pipes and affect valves in appliances if not reduced with the use of a water