Sewer Line Capacity.
Sewer Line Capacity.
(OP)
I have looked through the forum trying to find something to help me. I am trying to find the capacity of an old sewer line. I am Upgrading a Treatment plant and need to know the capacity of the trunk sewer leading to the plant. The trunk line is bass ackwards. It goes from a 12" VCP to an 8" DI/PVC into the plant. The 8" line was fixed with PVC thats why its half DI PVC. Do I use Mannings or HW equation? Also I have the Slope of the lines in % how do I convert it for the equations?





RE: Sewer Line Capacity.
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Sewer Line Capacity.
RE: Sewer Line Capacity.
RE: Sewer Line Capacity.
If you're just needing the identify the capacity of the line (independent of the plant upgrades), I agree with cvg's recommendations above. You'll have to make some assumptions about what a "reasonable" headwater would be. Again, I'd also check the regulations to see whether they'll allow you to consider pressure flow for a gravity line. Most regulations I'm familiar with require gravity pipes to pass design flow at half full.
RE: Sewer Line Capacity.
The 8" pipe no doubt flows full>
The capacity of the trunk sewer is its surcharged capacity not its free flow capacity. So the equation you should be using is a full pipe flow equation and the gradient you should be using is the hydraulic gradient not the pipe gradient. The hydraulic gradient is the maximum upstream level in the manhole - discharge level in the plant.