Roughness values for aged GRP pipes

[waseem19]

Hi,

I ran a Google search looking for this but nothing came up so far.

Does anyone have a technical paper or a guide in estimating pipe roughness over time (more than 10 years) for GRP pipes ?

I would expect the roughness to be directly related to the type of fluid transferred, velocity , temperature ?

in my case its a 12 years old GRP pipe, transferring treated effluent at a velocity of 1.0m/s .

thanks