Yeah, a 2 inch pipe will handle more flow than two 1 inch pipes. So the water will flow much easier once it gets into your 2 inch, but its the trip from the overflow to get to that 2 inch pipe that still slows things down. I was actually all set to buy a new bigger pump for my tank until right at the last minute I thought to check what overflow could handle. I'm glad I did as I would have had water all over my living room carpet soon after turning on that new pump! LOL