Perc tests are done after the test pits; the test pit reveals the limiting factors within the tested areas. At a minimum of 2 perc tests are required per area (primary & replacement). The test will be within that densest area 1 to 3 feet below the infiltrative surface of the disposal system. The hole is dug and prepared and water is added to the hole and the water drop is measured over a specific drop interval and timed for 7 consecutive runs. The data is then logged and a percolation rate is extrapolated from the data and used in the wastewater disposal system design calculations.