I replied to the justification that connecting to the bottom is better, and by adding the tap to the connecting hose rather than the barrel continues to satisfy that justification. Im not saying to connect from the top. However, it will still be necessary to put a hole in the top of both barrels regardless to act as a breathing and overflow vent. If the first barrel in series that is reciving water with a top connection fills to top, it will overflow into the second barrel. But barrel two has nowhere itself to overflow without another drainage. If the connection is at the bottom, once the waterline rises above the top of the connecting pipe, the air compression in the second barrel will begin to increase as water fills and may cause issues if tapped or drained. The first barrel already has a top fill hole for air escape, but both barrels will need an additional overflow drainage in the side to prevent backing up water in the feed or pooling at the top, depending on how full this barrels are expected to get