I have found a great solution to this...(better than any professional version I have seen on the web.)
Colebrook-White equation is the currently accepted world standard
1 / λ1/2 = -2 Log [ 2.51 / (Re λ1/2) + (k / dh) / 3.7 ]
Contact me , Send me a list of the dh, k, and Re values (in excel) and I will quickly show you.
Ragknot@gmail.com