A soil permeability apparatus is a device used in geotechnics to measure soil permeability, especially those with low permeability, such as clays. It is an important tool in environmental and geotechnical engineering to assess the hydrogeological conditions of the site. The apparatus consists of a series of needles (tubes) of different diameters which are inserted or drilled into the ground to a certain depth. The measurement is carried out by putting inserting water under pressure to the ground through the needles and monitoring the rate of absorption or spreading in the ground. On the basis of changes in the water pressure in the needles and the duration of the test, the soil permeability coefficient can be calculated. This method is the most effective in the case of low permeability soils. In the case of high permeability soils (such as sand) this method may be less effective.