This combination permeameter has a transparent plastic chamber for soil specimens of either fine-grained or coarse-grained soils. Generally, soils containing 10 percent or more particles passing a 75 μm sieve are tested using the falling head assembly. More granular soils, containing 90 percent or more particles retained on the 75 μm sieve, are tested using the constant head
assembly.

The cell is sealed at the top so that a vacuum may be used to saturate the specimen. Porous stones located at the top and bottom of the cell prevent sample flaking or washout. For constant head tests, a plastic funnel reservoir is mounted on an upright attached to the cell, providing a maximum head of 550 mm. Falling head tests are performed using the graduated pipette falling head reservoir, which gives a maximum head of 1000 mm and is graduated 0.2 ml.