To begin with, I'm not even sure that what I'm looking at is a packing nut, but it looks like it would operate similarly to one in shower/bathtub valves. I'm adding a ProFlo water hammer arrester (arrestor?) to my dishwasher's supply line and it looks like there's a bolt inside that can be turned with an Allen wrench. I can't find any documentation on the part that mentions this adjustment.
I'm worried that if this is a bolt that puts pressure on a packing nut, then installing the arrester without tightening it could let water get into the piston mechanism and render it ineffective. But if I tighten it too much, it could keep the piston from moving quickly enough, which would also render it ineffective.
Is this meant to be adjusted?