king bubba
Member
Not sure what you are referring to when you ask about the "coupling". In a std Durso, it is always best to have the Durso a slightly larger diameter than the bulkhead it is to feed thru IME. In a vertical (Stockman) my experience is that either the same size or slightly larger will work but the latter will give a little better performance. I have never had any success using a smaller "el" into a larger "T" section. Finally, if your total run to the sump or whatever is much over a foot or so in length use 45 degree elbows instead of 90's for quietness and be ready to add a reducer bushing at end of the run. 1" pipe = 3/4 " bushing. Better control and stability and usually a little quieter because of added backpressure. Stockman used several small holes in his pipe to keep critters out but he was more concerned with clogging. IME a pair of holes opposite each other and a diameter at least half that of the pipe itself eliminated any chance of clogging. IMO critters shouldn't be able to get that far in the first place. Hope I am helping and not confusing.