Just FYI: the correct Radiator Drain Valve is Horizontal, NOT Vertical. My 2010 6.1 only had 8503 miles on it when I got it 3-weeks ago, so I let a shop Chem-Flush the system, and change the Overflow tank. Got up the next morning and had a puddle. Could not see and leaks, but tank was empty, so I swapped back to the original "Stained" Tank. Drove it about 50 miles, everything looked fine, then about an hour, had a puddle. Pulled the cowling and saw THIS. 1/2 turn and all is well again. Showed pics to the shop owner, and he said he would be discussing this with his tech
FYI, If you are going to do any kind work on your car, do yourself a favor, take a photo of it first.