setting up 135 - plumbing issues (SOLVED)

[marshall.read]

i'm setting up a 135 reef. i put in a 4' calfo box which housed three 1" bulkheads. each 1" bulkhead has a durso standpipe outside the tank with a slightly less than 1/4" hole in the top of each. i have from multiple sources that a 1" pipe should gravity flow approximately 600 gph, so i assume that my setup should be able to handle at most around 1800 gph. for the return pumps i will be using two mag 9.5's, which at 5' of head should push around 750 gph, so i'm assuming i'll have around 1500 gph total.

so i set it up last night using only 1 mag 9.5 (the other is still running my 75 gallon) and to my surprise/dismay the three drains are barely able to handle the flow and the pipes are bucking around slightly which to me would indicate that i'm trapping air. i measured each line individually and i'm only getting about 160 gph from each drain, so for all three i'm pumping less than 500 gph and the pipes are barely able to handle it. i drilled a second hole into each durso for more air flow to no avail. later today i'm going to try to put in an airline tube down the durso to see if that helps.

in case its related (and i'm starting to think it is), my drain lines don't drop vertically down, rather they go at 45degree angles. the reason for this is because i got a little drill happy and put in the holes relatively close to the center of the tank and then realized that the back of the stand is solid in the middle. my face is still a little red on that one. so i ran the drains at 45 angles to the bottom of the tank and then straight down to the sump/refugium. i included a picture for reference (its very crude as i drew it in a hurry using ms paint, but i think it should do).

so any ideas on what the problem/problems is/are. i'm hoping the airline will solve my problems, and i will update this post if it does so. i'm thankful for any help or advice.