You think a 2" pipe isn't that much larger than a 1-1/2" pipe? Basic high school math taught us that the area of a circle is Pi (3.14) times radius squared. That means a 1-1/2" pipe has an area of 7.065 square inches. A 2" pipe has an area of 12.76 square inches...that's almost twice the size. I don't know if that really answers your question, but it's a stat that may be relevant. Apply the same formula to water pipe and you may be amazed at how much the area is increased by going for 1/2" to 3/4" for example. We tend to think that it's only 1/4" inch difference or in your case, 1/2" difference, but when the radius is squared the difference is quite apparent. Yeah, I know, you probably thought you'd never have a use for that math stuff when your teacher taught the lesson. I fought that sort of thinking for 30 years as a teacher. You'd be surprised how many times former students have said to me, "Why didn't you make us learn that?" Well, I tried everything but sever beatings, and even that was tempting at time. LOL.