How to carry out a percolation test

Do-it-yourself soil rapid test

The building owner can roughly estimate whether the subsoil is generally suitable for rainwater infiltration using the following quick soil test:

1. Dig a pit measuring 50 x 50 x 50 cm with a spade. The floor should be level.

2. Cover the ground with 1 – 2 cm of gravel or chippings and attach a ruler to a stick driven into the ground.

3. Water the pit for about 30 minutes to moisten the soil. Before the experiment begins, the pit must be completely emptied.

4. Fill the pit with approx. 20 cm of water, note the time and water level.

5. Check the water level after 30 minutes. If it has sunk less than 2 cm, check again after 120 minutes.

6. Try again a second time. If there are deviations from the first attempt, a third run is necessary.

Evaluation 30-minute test:

  • 0 – 2 cm infiltration height: very low soil permeability  (clay/silt)
  • 2 – 16 cm infiltration height: low soil permeability  (fine sand)
  • > 16 cm infiltration height: medium soil permeability  (medium sand)
  • 20 cm in < 3 minutes: good soil permeability  (gravel)

Evaluation of 120-minute test:

  • < 4 cm infiltration height: insufficient soil permeability  (no infiltration possible)
  • 4 – 8 cm infiltration height: very low soil permeability  (clay/silt)
  • > 8 cm infiltration height: low soil permeability  (fine sand)
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