Doing the Presoak

• 1). Plan your proposed area for the septic system. Use a chalk line to mark it off, so you know that you're working in the right area when you do the perc test. Research with the local utility company to make sure that your proposed area doesn't interfere with any city pipes or underground wires.
  
  
• 2). Dig your holes for testing the soil. Holes should be evenly spaced at 30- to 40-foot intervals within your proposed septic system area. Do not place holes less than 30 feet apart from each other. Dig holes 2 feet deep (this is the depth of most sewer system trenches) and anywhere from 4 to 12 inches in diameter. In winter, dig holes in the middle of the day or afternoon, when the soil is softened by sun exposure. Do your test during dry weather, so that the ground is not saturated. Dig at least 6 such holes.
  
  
• 3). Dig a separate test hole at the lowest point of the site. This hole should be 48 inches deep, to test the depth of the water table in the area. A water table that is within 48 inches of the surface with interfere will a septic system and the soil's ability to absorb sewage.
  
  
• 4). Remove any loose soil from the holes, and use the saw blade or knife to rough up the sides and bottom of the test holes. This will increase the seepage rate and give a better estimate as to the suitability of the soil for a septic system.
  
  
• 5). Pour water into each test hole and maintain the water level. The level should be at least 12 inches deep for at least 4 hours. Rainy weather in winter might help to maintain this level but will also negatively affect the soil's ability to absorb moisture. Perform this presoak in the afternoon.
  
  

Measuring the Seepage

• 1). Prepare your stakes for measuring the amount of seepage into the soil. Hammer nails into the stakes at 3 inches from the bottom, 9 inches from the bottom and 29 inches from the bottom. Prepare one stake for each test hole.
  
  
• 2). Conduct your test on the day after the presoak. Clean out each test hole, including any water and silt left in the holes. Drive a stake into each test hole until the 3-inch nail is resting on the soil at the bottom of the hole. Each stake should be able to stand on its own in this position.
  
  
• 3). Fill the holes with water up to the 9-inch nails. The water level in each hole will be 6 inches at this time.
  
  
• 4). Measure the water level after an hour and record how much the water level has dropped. Refill the hole to the 9-inch nail and repeat at hourly marks at least 3 more times.
  
  
• 5). Give your measurements to the officials at the local Health Department to be graded for septic system suitability.