Help need Clarification

[fernalfer]

Ok i have 2 pics below showing a durso drain pipe which is 1 inch going into the bulkhead and a return pipe which is 3/4 inch going into the bulkhead. Now the thread side is wider on both sides but fits the holes on the bottom of my tank perfect. (The thread side that is.) So what size bulkheads are they? Is the one with the return pipe being 3/4 going into a 1 inch bulkhead or is it a 3/4 inch bulkhead? Also same question with the drain pipe bulkhead. what size is it.

Reason why i ask is because everyone is saying the trigger systems sump has 1 inch bulkheads yet the bulkhead that my 1 inch durso goes into does not fit. but the bulkhead that my 3/4 inch return pipe goes into does. Confused......

 

[fernalfer]

see the 1 inch pipe fits in bulkhead but bulkhead does not fit in trigger systems hole. But the one inch pipe not in bulkhead fits through hole