Herbie overflow

[pastelball]

I am seeing up a deep blue 34 gallon with a corner overflow. I had the return drilled in the back for a 3/4" return. It has a 1" and and 3/4" in the bottom. Due i use the 3/4 in the bottom for the main to the sump or the 1"?

 

[Hbreef]

Both drains will go to the sump, but you want your 1" drain to be your main and your emergency drain to be your 3/4"

 

[pastelball]

Cool, thanks.

 

[Even Further]

I wouldn't do it like that. IMO use the 3/4" for the siphon, and the 1" for the emergency. This is a 34 gallon tank. And, you're going to dial back the gate valve on the 3/4" siphon line to tune with the return pump. The 3/4" pulling a controlled siphon will more than handle a 34 gallon. The emergency should be the larger of the 2. The Herbie emergency inlet is at the water line in the overflow box, it will likely never pull a siphon because it will suck in some amount of air. That's assuming you plumb like most do, with 2 vertical pipes.