cleaning copper cfc

Last weekend I recirculated a gallon of vinegar 5% thru the chiller occasionally closing both in and out valves to capture the vinegar inside for a few minutes.  Then recirc some more.  repeat.  did this for about an hour kept getting blue/green water after changing to fresh vinegar.  Got more vinegar this week and running it again, same results only lighter color.  Is the blue green color indicating its still cleaning or am I eating copper?  I have used this method before and it never took more than a couple gallons to clear.

Your vinegar is slowing etching away the copper. You are basically eating your copper tubing away from the inside out.

That's what I was thinking.  But after googling 'how to dissolve copper'  and 'how to dissolve copper oxide' I am not so sure. 

Just flush it with water. Although the vinegar is dissolving copper oxide, the reaction of a little acid and air is creating a whole new layer. 

When you sanitize or clean with vinegar or any acid, you only need 4 pH. A dull layer of oxide is fine.

I flush it with hot PBW right after brewing, followed by a starsan flush then compressed air, then next brewday I flush with starsan before chilling again. Do you think the vinegar cleaning is not needed, I do this about once a year.  Starsan at the proper strength is good enough?

Yup! I think that's plenty good and the vinegar is not needed. The PBW right after brewing is going to get rid of solids. Recirculating it for a while would be the most thorough. The Starsan followup is neutralizing any PBW residue (which is a good thing) and giving a nice acid rinse. Beyond that, just a water flush before using the compressed air will keep it from going green.

Thanks I'll scratch it off the list

Just run boiling water through it before you use it and clean with PBW from time to time. No need to go crazy on it.