Horizontal Drainage Pipe - Required Slopes

Minimum pitch of horizontal drainage pipes. Drainage piping and recommended minimum slope or pitch.

Pipe Diameter (in)	Pitch (in/ft)	Pitch (m/m)	Gradient
under 3	1/4	0.02	1:50
3 - 6	1/8	0.01	1:100
8 or larger	1/16	0.005	1:200

Conversion Factor

1 in/ft = 0.083 m/m