These calculators are based on corrugated polyethylene pipe. Calculations for concrete and clay pipe can be approximated by using the smooth pipe option.
Pipe Diameter (inches)
Use this calculator to compute the required pipe size for a given area and % grade.
Smooth Interior Pipe? Yes No
Area Drained:
Acres: % Grade*
*%Grade is the feet of fall per 100 feet of length.
*Use commercially available size equal to or larger than size shown.
**A minimum velocity of 1.5 ft/sec should be used when fine sands and silts are present — otherwise a velocity of 0.5 ft/sec is sufficient.
Area Drained (Acres)
Use this calculator to compute the area that can be drained by a pipe of a given size and grade.
Pipe Diameter (inches): % Grade: *
* %Grade is the feet of fall per 100 feet of length.
Flowrate Calculator
Use this calculator to obtain flowrates for a given area, for various drainage coefficients.
Area drained, acres:
