Im not sure whats the issue, but even if i use FTBChunks and chunkload the area and go back to overworld i can see my tank draining even tho its hooked up to an infinite source, im not sure if its a problem with the tanks themselves or the chunk loading.
Is there a way to fix this or should they be working and something is broken?

Can confirm. Have the same issue but with the enderchests of the same mod. The items get clogged on one side (even though both sides are chunkloaded through FTBChunks) and as soon as I go to the recieving end it empties what's in the ender chest but doesn't transfer the input from the previous side.