I need all items (ice) to stop flowing in to my reactor when the filter isn't powered. Let's say my reactor is full on ice, but it has a slot for 32 ice. The filter pulls out a whole stack, and put's it in the reactor leaving 32 left over. Since that ice has no where to go, it gets stuck in the pipe. What I want is that when I unpower the filter, no residual items will flow back in to the reactor. Is this possible?
I believe a restriction pipe may solve your query... somewhat. It isn't stopping the issue from happening, but it's providing a solution.
The Restriction Pipe basically takes an overflow and pumps it elsewhere. For example, in your situation, it would take the excess ice, and pump it back to the chest/storage it came from (if you so choose).