Vinegar will cure that easily I get mineral buildup on the tap and takes it right off after 20 min soak . a 1 gal jug of vinegar is 2.25 one line at 2 ft high other at 1 ft into bucket fill high line till low line runs to bucket and let set if your really worried about it. Me I will just purge line when done with compressed air so hard water doesn't sit in line.