How do I redirect items to fill one column of chests at a time?
Solution 1:
Here's the setup you have. (red arrows show hopper direction, red circle indicates hopper pointing down)
You'll need a setup like this instead!
The green circles indicate that another hopper is below it to collect items; we'll call them the "unloading hoppers". With your old setup, whichever "column" the items landed in would be the chest that they end up in. You need to lead your items into the first unloading hopper, which will go to the 2nd once it fills up, and so on.