threaded bulkhead question

[BCWolfen]

Thanks all. I have an overflow that I plan to use as my primary line down to the sump. Initially I had not wanted to drill the tank. But now that its going to be empty for a bit, I thought adding at least one bulkhead won't hurt. I figure having a seperatly plumbed drain down to the sump set a bit higher than the overflow will help prevent 'spillage' if the one blocks. So I guess I'll get it drilled for a 1 1/2" and go from there.