I'm pretty sure it's the other way around, it gets sucked up through the white pipe
Make absolutely sure that the outlet on your DI is the outlet to your system, it should say in and out on the screw head.
5l is a bit low, make sure you fill it 3/4's, shaking the vessel while filling it, and stomping the bottom on the floor a couple of times, so the resin settles nicely.