1/2" whole way.Will water pump shoot out faster if you run 3/4" feed line and reduce it to 1/2 " for each bucket or will it be the same as if you ran 1/2" the whole way?
Do not use spade bits. take ut from someone who has used both. you need to test the holes in a lid like I told you @NamoYou'd be better off with the proper size spade bit... I don't know if this one is the right size for the grommet you need to use.. Its the two little teeth on the outside of the bit that cut through the plastic to make the hole.... Those stepped bits aren't the best for the job.....
http://www.homedepot.com/p/BLU-MOL-1-1-8-in-Dia-x-6-in-L-Xtreme-Spade-Bit-3393/205624212?cm_mmc=Shopping|G|Base|PLA|D25T|PowerTools&gclid=CLuw09Sw3dACFQhqfgodcNsKXg&gclsrc=aw.ds
Lets see what he thinks when he tries it. Maybe he'll buy both and just return it after testing. Spade set at Harbor Freight is like $10.What makes you think i haven't used both?? I still think he'd be better off if he's drilling holes for a grommet and barb... Guess i haven't read enough of your grow threads to be impressed with your choice of bits...