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Pumped outlets for subsurface drainage

Generally speaking, surface drainage isn’t as effective as subsurface drainage for satisfying the drainage needs of many soils.

Enhancing surface drainage with subsurface, or tile, drainage can potentially improve crop productivity and farm efficiency where wet soils persist. Compared to surface drainage alone, improving tile drainage reduces runoff and peak outflow rates—in some cases, dramatically.

Tile drainage may decrease sediment, phosphorus and organic nitrogen. However, it may lead to increased losses of mobile constituents, such as nitrate nitrogen and some salts.

What pumped outlets are

Pumped outlets (Figure 1) can improve drainage at a reasonable cost in areas that lack a natural gravity outlet. A pump drainage system consists of a:

  • Collection system (tile or surface drainage system).

  • Pumping plant.

  • Free outlet.

Figure 2 shows a typical pumping plant.

Pump station
Figure 1: Pump station. Photo: Gary Sands.
simple drainage pump station
Figure 2: A simple drainage pump station using a submersible pump.

When to use pumped drainage

For pumped drainage to be feasible, weigh the economic benefits of improved drainage against the startup and operating costs associated with the pumping plant. Locally assess potential economic benefits, as those depend on the:

  • Adequacy of the current drainage system.

  • Soil texture.

  • Crop to be grown.

Operating costs depend on the pumping plant design—in particular, size of the pump and lift—and rainfall characteristics over the drainage season.

Planning pumped outlets


Gary R. Sands, Extension engineer

Reviewed in 2018

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