Overflow either flushing or gurgling :(

[vanreefer]

I have a problem with my external overflow box ( or I guess below the box)... I built a durso to fit in the CPR overflow... and I either have to keep the hole on top of the durso so small that it sucks air or it does the whole flushing thing. I originally had the 1" pipe entering the water in the sump vertically... read that was a faux pas so I put a 45 in the pipe and had it enter on a 45... same problems... So I went out and bought a 1"-1 1/2" expander attached a 1 1/2 " 90 and a T on the end... same problem... of course the tank is in the living room and I think my roommate is about to put a brick through the tank to quiet it... which would probably work but there has to be another alternative... Any explanation or even pics (prefered) that you have would be verrrrrrrrry much apriciated (sp?)
TIA