[CaptainGizmo]

Brad yes you can reuse a compression fitting, buy a few new ferrules and the brass sleeves (these keep the plastic tubing from cutting when tightening).

I need further education.  So I’ve seen where I can buy replacement sleeves and nuts, but haven’t seen ferrules.  I somehow assumed the ferrule was permanently attached to that side of the fitting.  Also, to clarify I assumed the ferrule is the part that fits inside the tube?

Speaking of replacement nuts, is there a need for them or are you generally fine using the same nut with a new sleeve?

Brad,

We need a little bit of terminology clarifcation here:
The fitting consists of the body, the compression sleeve (or sometimes called a ferrule), the insert, and the nut.

Yes, the SLEEVE should be replaced when you break the connection; the rest of the components are reusable.

This is an example of 'Best Practice' versus, do I HAVE TO.  Many times, the sleeve "could be" reused, such as in an emergency when you don't have a new one.  But, even if I have to "rob" from another spare fitting, I'll always replace the sleeve with a new one.  Easy to buy another pack when convenient.

As to the INSERT, not every fitting has one.  As you've found out, they are loose, not a fixed part of the fitting.  Those are generally designed for to help the nylon brake tubing maintain it's shape/diameter under the compression of the sleeve.  Inserts aren't used for rigid tubing such as copper.

Hope this helps.