How big pipe is needed for 1 cubic meter per second of water?

Let's say that in 1 second, n meters of water come out of the pipe.

We have a cylinder of length n, and of an unknown radius.

The volume of this cylinder is n*pi*r2, where r is the radius of the circle.

We have our equation now: n*pi*r2=1.

r2=1/n*pi.

r=√(1/n*pi)

So, if n meters of water come out of the pipe per second, then you will need a pipe of radius √(1/n*pi) to output 1 cubic meter of water per second.