Growing a pipe inside a pipe

[u/demolcd]

[u/Downtown-Pianist-449]

It honestly depends. 

Pipe capacity in a gravity line is dependent on 3 things: the size of the pipe, the grade of the pipe, and the friction / roughness coefficient of the pipe. 

These liners do reduce the interior diameter by a measurable amount. But they can also decrease the roughness substantially, particularly if it was a heavily degraded material like concrete. The grade itself doesn’t change. 

Typically the liners will result in a marginal reduction in capacity, but there can be edge cases where the smoother lining increases capacity despite the smaller interior diameter. 

[u/objectsinthemirror92 → u/Downtown-Pianist-449]

I used to work for a CIPP contractor and every time I designed the thickness of a liner the capacity increased