The most common reasons why you may experience air in the tubes are related to installation:

 

1) Most common reason is if the breather holes are not open.  The breather holes need to be open so that the system can "breath" and release the vacuum of air, so that ink can flow.  Please ensure that the breather holes are open (check your installation instructions for reference to breather holes)

2) Another possible reason is if the system is not on a level surface with the printer.  If the system is "below" the printer, gravity will prevent the ink from flowing properly.  So please make sure the ink is on the same level surface as the printer (not above, and not below it)

3) Less common, maybe the cartridges themselves did not have the plastic pierced when you inserted them in the printer.  Check the outlet ports of the cartridges to ensure that the plastic coverings have been pierced so ink can flow through them.

4) Priming.  This is usually needed, and will get ink to siphon to the cartridges.  This can be accomplished by either running a print head cleaning cycle on the printer and/or also extracting air bubbles by following the attached procedure (note that for Epson, you can follow BOTH the "epson-airbubble-removal" instructions attached, AND the "CIS EXTRACTING AIR BUBBLES HP & CANON" instructions).  Doing both will help.