Measure Percolation.

Determine the capability at which your soil absorbs liquid.

Percolation Test Guide

The percolation test is designed to determine the suitability of a site for a subsurface private sewage disposal system (i.e. septic system). More specifically, a percolation test measures the ability of the soil to absorb liquid. Septic system designers use the results of percolation tests to properly construct septic systems.

The percolation tests are designed to simulate conditions in a septic system. The percolation test consists of a hole 6-12 inches in diameter dug in the area of the proposed septic system. The depth of this hole varies depending on the soils encountered but it is generally not greater than 24 inches. The hole is initially filled with water (presoak) in an attempt to saturate the soil, allowed to drain away and than refilled with approximately 12 inches of water. The rate at which the water drops in the hole is measured at intervals over a period of time ranging from 30-60 minutes. The uniform slowest rate of drop of the water level over a measured time interval is converted to minutes per inch and used as a basis of design in determining the septic system size. For example, if the water dropped uniformly 1\4 inch every five minutes the rate would be 20 minutes per inch. The Health Code provides a simple table that determines the size of the system based on the measured perk rate and the number of bedrooms in the home. The greater the number of bedrooms and the slower the percolation rate, the larger the system required. Commercial systems are sized using the perk rate and projected estimates of water usage in gallons per day.