I have three acrylic tanks stacked with a single eheim 1260 from the bottom/sump to the top. Each tank has 1" drilled bulkheads on the back edge (not bottom) that is plumbed with 1.5" pvc to the "return" of the tank below it. The bulkhead has an attached T (actually a sloping T, not straight drop, to make it quieter) with a cap fitted on the top (undrilled cap as of now). The problem I'm having is my return (eheim 1260) has a greater volume than my bulkheads are pushing. Yes, I can dial down the return with a T & gate valve, but would prefer not to. I'm looking for ideas on getting better flow through the bulkheads, quiet flow if possible. I initially had a 90 elbow pointing down, then sideways, then no fitting...I'm wondering if the lack of head/water pressure is giving too small of a push down the overflow?