Recommended Slope for a Drainage Pipe

In the majority of new construction projects, drainage pipe is the first piece of plumbing to be laid, allowing plumbers to work from the ground up, installing the plumbing within a structure.

Slope

The recommended slope of a drainage pipe from its coupling with the building's waste lines to the exterior sewage pipe is ¼ inch per foot of pipe, according to Plumbing Basics. In some instances this is not possible as the ¼ inch per foot would take the drainage pipe below the level of the sewage pipe.

Types

Drainage pipes in 2010 are made of either rigid or flexible wall plastic pipes made of materials including polyvinyl chloride and polyethylene. Thinner versions of flexible piping can cause problems with the slope of the drainage pipe because the slope can be altered by defects in the pipe and in surrounding ground.

Grade

Steeper grades of piping are used when necessary, but the ¼ inch per foot allow a certain amount of self cleaning of the pipe to take place. The drainage pipe is laid from just outside the exterior wall of the structure and runs inside the structure.

References

• Plumbing Basics: House Drain Plumbing Info
• Department of Ecology: Drainage System Components