I have to agree...having an interconnect on both ports between cards isn't likely to improve performance. You're basically giving the water a straight line shot passing by both blocks without circulating through them.

With most GPU blocks I've seen, water enters the block through one port and then is forced to circulate around inside the block before it can exit the other port. This is done by physically blocking the flow of water so it can't just scoot sideways from one port to the other and then out. You're bypassing that intentional blockage by having the left interconnect (based on your picture). Remove the left interconnect, leave the right one, and water is forced through the block of one card, then through the interconnect, then through the second card, then out.

With both interconnects the way they are in that picture, water entering the first block has two options: (Assuming the bottom card is the first one in the loop and water exits the assembly through the top card).

1) Push the water that came before it through the block, then through the right interconnect, then through the second block, then up.

2) Push the water in the left interconnect up and then exit through the top.

On the other hand, if the loop is set up so that water is entering the top card first and then down through the bottom, I would expect it would be even worse because you'd have the added issue of gravity encouraging the water to just go straight down without circulating through the blocks.

Water will take the path of least resistance (just like me ), which means the flow through the blocks with your current setup will be slow at best, stagnant at worst.