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?

Angle view of interior bolt/nut

Full side view of arrester


This should not affect your water seal, which is the o-ring.

It's probably just an assembly detail, particularly if the instructions don't mention it.

I don't see any way it would affect the piston, which is at right angles to it.

My best guess (and it is a guess) is that it's a way to install an orifice (small hole of precisely known size) at the time of assembly. EDIT: Actually, it may just be a mechanical requirement of getting the compression nut in place, looking at it again.


To me that’s looks like the compression type the fitting in the center is to prevent the tubing from collapsing. I have used them a few times and believe you have the same, they also make them with 1/2” npt fittings but I use pipe stubs when I have pipe.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.