I racked the FlexTank and WinePod this past Sunday. Since the WinePod is used only for primary fermentation, I transferred the wine to four 5-gallon carboys. The FlexTank is capable of handling secondary fermentation, so I transferred that wine to a clean FlexTank.
After 22 days, the Brix measured 0 degrees (SG = 1.0) in the FlexTank and 5.5 degrees (SG 1.022) in the WinePod. The WinePod sugar sensor was out of calibration, and showed a reading of 3 degrees Brix. I'm not sure what caused the error, whether it be from the accumulation of yeast at the bottom of the tank or just a faulty sensor. No matter how it is measured, the wine fermented slower in the WinePod than the FlexTank. It will be interesting to see whether this results in any differences in the final product. I assume the wine that was in the WinePod will continue to dry down (maybe to zero) now that it is transferred to the carboys. The ambient secondary fermentation temperature has held constant at 62 degrees F, but may drop a little over the next month as the outside ground temp drops.
Besides the lack of fine temperature control on the FlexTank, my biggest criticism is that the caps do not fit properly on the lids. Of the five 80-gallon tanks, the caps and pressure valves screw in properly in only two of the lids. The others require a set of pliers to tighten the cap (owing to misformed grooves in the lid). Using pliers on plastic caps is far from ideal, and the caps were nearly destroyed after the first year of use. In addition to the cap issue, I found out very early that any metal surface on the FlexTank is highly susceptible to rust if not completely dry. After cleaning a tank, I unscrew all metal components, including the drain valve and tasting valve, and dry and insert paper towels on the metal surfaces. This process seems to work, but it is a pain to always remove and replace the screws. I also managed to strip one of the tasting valves (which is made of plastic but screws into a metal fitting 1/3 of the way up the tank). While annoying, these steps are a far better alternative than allowing any rust to form on the tank.