[Thomas Gaudich]

Dear Sir: thank you for calling me an expert, but unfortunatly i'm far from that. About your question, you should check some literature about this problem, because, with your data, your're probably within the limits of a laminar flow. In this conditions, the friction factor is independent of the roughness of the pipe. As far as i know, in laminar flow conditions, the friction factor is given by f=64/Re, being Re the Reynolds Number. With your data, the Reynold's number is about 2546, wich is near to the limits of laminar flow (see, for example, Poiseuille's formula). As conclusion, i don't think you can calculate the factor by Colebrook's equation, in this conditions. But, as i first said, i'm no expert, so you should check this. Anyway, i've used your values in my worksheet and it returned the values of:
Laminar Flow
'f' calculated by the above formula = 0.0251
Turbulent Flow
Rough Pipes
'f' calculated by Colebrook's equation for rough pipes: 0.2720
'f' calculated by Karman-Prandtl's equation for rough pipes: 0.2674
Smooth Pipes
'f' calculated by Karman-Prandtl's equation for smooth pipes: 0.0133
'f' calculated by Nikuradse's equation for smooth pipes: 0.0376
'f' calculated by Blasius's equation for smooth pipes: 0.0445
Hope this helps and please let me know if you find any errors in this values.