I should note that my overflow consists of (3) 2" bulk heads in the floor of the tank. I built the oveflow kind of in a "T" shape to cover all 3 bulk heads. The main riser is large enough to accept the the flow from a hammerhead pump, which 2 -of the 3 bulk head are about 95% capable of drainging, and have a center 2" pipe catch the remaining as a overflow safty. It works well.
My whole system is plumbed both ways with 2" piping.
2" supply line to tank is split under the tank into 4- 1" outlets for the ocean motions.
2 of the 3 drain bulk heads plumbed into 1 common 2"return line to the sump
the third center overflow bulk head is plumbed into its own 2"return line to the sump so I can see at the sump exactly how much is going over the over flow safty.
I did this so without creating a flood when I take my chiller or skimmer off line for maintance, without shutting down my system. The center overflow can handdle the additional volume. Kind of overkill, but I know I am not going to accidentally overflow the tank.
