The water replacement test method is used in coarse-grained sands, gravelly sands, in mixed soils (slope debris) in which stable pits can be excavated. Water replacement with the help of a plastic film or soft rubber skin allows to measure the volume in very permeable coarse-grained soils.

The volume of the test pit (V_g) is determined from the mass of water required (difference weighing of the bucket before and after) and from the density of the liquid used in each case ρ_F. For water, ρ_F = 1.0 g/cm³.

Volume (V_g) = mass of water required / density of liquid used