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University of Minnesota Extension

Extension is expanding its online education and resources to adapt to COVID-19 restrictions.

Drainage slide rule

With a pocket-sized agricultural drainage calculator, you can:

  • Compute the required pipe size for a given drainage area.

  • Compute the acres drained for a given pipe size or grade.

  • Estimate permissible flow velocities for any pipe size, based on grade.

  • Compute flow rates for pipe sizes or grades.


  • Functionality for both corrugated and smooth-wall materials.

  • Built-in roughness coefficients.

  • Other design and look-up tables.

Order your slide rule

Contact drainage@umn.edu to order a drainage slide rule or request more information.

Drainage slide rule
Drainage slide rule

Gary R. Sands, Extension engineer

Reviewed in 2018

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