I think once you have a control valve on the drain it no longer qualifies as simply a Durso.
I did lots of things on the 180 I never tried before. The drains go sideways 15 feet almost but not completely horizontal. I made sure with a level.
They are lowest right under the tank and slowly rise toward the sump area where drains empty. There is very little head compared to what people usually have, 10 inches if I remember right
I combined the 2 drains on the tank into one larger pipe under the tank.
There is a 1.5 inch ball valve on the drain I can close to open the union but I do not use it to control the drains. The Durso drains, weir and pump size do that. The 180 has 2 1 inch drains combining into a 1.5 inch pipe back to the fish room. This drain always has air in it.
The 240 has 2 1.5 inch drains with valves and 2 without that go straight down behind the tank, through a wall and back up to the drain area.
I have the pipe rise above the sump tank with air vents so the air can leave the pipe at one end or the other. The water leaves through a tee sideways and travels to a pipe that is submerged slightly.
It did have bulkheads in the tank so the 4 drains could enter into the bottom but I redid that when I added the 150 gallon stock tank for the 180 addition.
Sump setup 1 for 75 and 240
The 2 drains for the 75 empty into what is the return section and approach from the left. The smaller tub on top has the 4 drains from the 240.
Sump setup now
40 gallon drains to 150, 150 has 2 2 inch drains into 100.
This picture shows the 5 standpipes. The head on this system is the difference between the water lever in the tank and the height of the tee.
It's not much.
before skimmer upgrade and second surfer reactor
How to connect 2 non parallel surfaces through any angle. Takes a little planning to drill the holes in the right places based on the radius the length of the connecting pipes. The holes have to be offset this radius. The bulkheads sit without force on them and don't leak.
Since the 100 and 150 stock tanks are only 4 inches different in height in a shutdown both can catch drain back. The 240 and 75 filled the old single 100 gallon stock tank to within 1 inch of the top.
Accomplished with WV TLAR engineering. That Looks About Right.