- "Perk," which is also sometimes spelled "perc," is short for "percolation." A percolation test is a test designed to measure the absorption rate of soil. The test is usually done to determine how quickly a given soil type will absorb water. Many jurisdictions require such a test before the installation of a septic tank or other such device that requires absorption by nearby soil to function properly and without causing too much pollution.
- The basic method employed in a standard perk test is relatively simple. A series of holes are dug into the soil, usually to a depth of between 3 and 6 feet. In most perk tests a minimum of 3 holes are drilled or dug, but some tests require a much higher number of holes. The number, depth, and width of the holes will be dictated by the scope of the project and by local regulations and laws. The holes are then filled with water and kept filled for several minutes with a continuing flow of water. The actual results of the perk test are determined by cutting off the flow of water and then measuring how quickly the water absorbs into the soil. The faster this process happens, the better the perk test score.
- There are many different factors that actively influence the results of the perk test. The absorbency of a given soil type will depend largely on the soil composition, the depth of the local water table, and local rainfall rates. Sandy soils tend to outperform other soil types in perk tests, and areas that are exposed to moderate rainfall outperform areas where there is either an abnormally high or abnormally low amount of rainfall. The percolation rate in areas with a high water table is much worse than that in areas with a lower water table.
