2 holes in overflow...which one for main drain?

[Canuck007]

So I have a 150 gallon that I am about to set up with 55 gallon sump. It has 2 holes in the single overflow...1.5" and 1" holes.

I want to go herbie method so which one should I use for the main drain? 1.5" or 1"?

I have heard both ways so not sure what to do.

Thanks!

 

[pelphrey]

Smaller drain with the gate valve, use the larger drain as the emergency.

 

[Canuck007]

Yup that's what i'm thinking as well. Thanks for your advice!

 

[TheEngineer]

Smaller drain with the gate valve, use the larger drain as the emergency.

This!