Bill you used diameter instead of radius. It is more like 27 sqin for the 6
inch pipe and 12 sqin for the 4 inch pipe not counting the small change.
Also about 48 sqin for the 8 inch pipe. Way more than using 2 of the 4 inch
pipes.

"bill" wrote in message
news
area= 3.14 x radius x radius. so the 6 inch pipe has cross section
of 100 sq inches and the two 4 inch pipe have 25 sq inches
On Mon, 04 Jul 2005 06:21:31 -0500, wrote:

I want to put a drain pipe under a sidewalk for rain drainage. I am
trying to determine the volume of a 6 inch pipe and a 4 inch. I know
that one 4 inch wont be enough, but am wondering if TWO 4 inchers
carry as much or more water than a 6 inch pipe. I have never been any
good at mathematics. I think I have to multiply 4 or 6 by 3.14, but I
am not sure. I will either use a 6 inch or two 4 inchers, which ever
holds more water. Or I may even go to an 8 incher. Alot of water runs
down the hill and keeps putting mud over the sidewalk. I need lots of
drainage volume.

Can anyone help.