theres a few ways to start the flow:
1. put everything together, keep the U-tube out. fill both boxes with water from the tank. (the drain side will only go so high) put an air line, or some form of small flexable hose in the U-tube. make sure to have a peice long enough to have a couple of feet left over. push the tube just past the bend. now just suck the air out. you may have to try a few times. you will see where the bubble forms, and you may have to adjust the air hose to get all the air out. once the air is out bite the hose and pull it from the U-tube. turn on the pump, make sure everything flows, and your done.
2. this is the cleaner way. again set up the overflow without the U-tube. fill the tube with tank water completely. then cover both ends with plastic wrap. place the U-tube in and remove the plastic wrap from the ends and your done. again turn on the pump, check the flow. enjoy
