Durso Durso Standpipes from Above
Most large tanks have two overflow chambers. One on the rear left and one on the rear right side of the tank. However, some large tanks use just a single overflow in the back center of the tank. This is an example of two Durso Standpipes being used in a large tank with just an overflow chamber in the center of the tank.
The Durso Standpipes are the lower left and right pipes. The two pipes in the center are return pipes from the sump into the display tank. The appendages off the return pipes are siphon breaks.
Dual Durso Standpipes
This may seem like an ideal solution but I personally don’t recommend it. It can be difficult to tune both standpipes getting the right air-hole size, etc. It’s hard to see when they are balanced or is one processing more flow than the other. If you are seeing a “flushing effect” which one do you troubleshoot?
Secondly since they share overflow walls, there is less teeth spacing to allow water to enter in the chamber. Typically two separate chambers can handle more water flow than a single combined chamber. Obviously there are many factors involved such as desired flow rate, teeth spacing (width and height), number of teeth, size of the chamber, etc — you may or may not run into an issue. Just be aware that issues do exist.