Anti-backflow for sump return?

  • We are currently upgrading MFK. thanks! -neo
here's a pic of the return. The tubing is 3/4 I/D. The grey elbow barely hangs over the side so if i have to drill holes, it will have to be on the black nossle thing.

return.jpg
 
If the "Y" in under water, you could drill them there. They do not have to be very big at all.
 
MonsterFishKeepers.com