I found the same thing when using bi-carb. I find that it's fantastic for light loads, but doesn't deal with things that are stuck on the dishes. So what I do is use bi-carb only when there's nothing heavy duty to come off (I rinse plates pretty well usually so this is a lot of the time, although that's probably a waste of water too ). Otherwise I use dishwashing powder, or a mix of powder and bi-carb. That seems to work well for us.