Decided to try out Craft Meister Alkaline Brewery Wash in place of cleaning carboys with PBW. Prepping carboys for the last two brews noticed small white streaks in the bottom of the carboys. I store the cleaned and rinsed carboys upside down to drip dry. Suspect the white streaks is PBW that did not rinse out.
I use less than 1 tablespoon of PBW in 2 to 2.5 gallons of water so I don't think the left over PBW is from a too strong solution for soaking the carboy over night. My cleaning and rinse water for carboys is 75° to 70°. PBW supposedly works best for cleaning when the solution is over 140°. Good temperature for clean in place systems but not for a glass carboy. The poor rinsing could also possibly be a reaction with minerals in our water which has a total hardness 183. Will have a couple of carboys to clean soon. See what happens.