Deffiniatly use plastic fittings with the Danners. Try to get nylon if you can (it is a bit softer than PVC). I have learned this the hard way by cracking the intake of my Danner 5 twice. Once was total stupidity from simply cranking the barb too tight, the second time was from lousy nylon reinforced vinyl tubbing "torquing" on the intake fitting, and a hair line crack appeared. My system is now down while a wait for a replacement impeller housing
