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Fairfax VA Perc Test: Basic Steps of a Perc Test

Perc Test

When most people think of septic systems, the image that comes to mind is a big tank underground. Folks don’t generally think about the drain field and the important role it plays in the whole system. The drain field’s ability to absorb the liquid effluent from the septic system is critical to the system. If one is seeking to build a home on a property that will require its own septic system in Fairfax VA, a perc test is a must before you even begin thinking of architectural designs and where the picture window will be. If the land isn’t suitable for a septic system, you may not be granted permission to be build or may have to find other, often more costly, solutions.

A perc test (also known as a percolation test) assesses the absorbency rate of soil. While the process is relatively simple, the steps are nonetheless precise and there are some particularities that must understood in the conducting of this test. A licensed expert in septic systems and perc testing is best qualified to conduct the tests.

What’s involved? Following are the basic steps:

  • Determine area where drain field is proposed. This ideally should be down slope of the proposed building area.
  • Dig test holes. These holes are typically about two feet deep are dug approximately 3 to 4 feet apart from each other, about 2 feet deep and 6 to 12 inches in diameter. The local health department may stipulate changes to location and depth of the holes. Once test holes are dug, fill holes with about 2 inches of gravel or sand.
  • Presoak holes overnight. Hole must be saturated with at least 12 inches of water for 24 hour period and longer if there has been little rain in Fairfax VA. Perc tests require moisture in the soil for accuracy.
  • Measure percolation rate. If presoaked holes have 6 inches or less of water remaining, the test can move forward. Carefully fill holes so that water is 6 inches above the gravel or sand. Record the water drop every 30 minutes for 4 hours. The drop measured in last 30 minutes is the absorption rate.

Once these tests are completed, the contractor and local health department will determine the suitability of the soil to support a septic system and its drain field. Both will work together to determine next steps with the land owner and what is permissible on the land in Fairfax VA. Perc testing thus is really an essential step. For more information, don’t hesitate to contact SES.

SES Company


  • Virginia Onsite Wastewater Recycling Association
  • National Onsite Wastewater Recycling Association
  • Water Environment Federation
  • Virginia Association of Counties
  • Northern Virginia Building Industry Association
  • Design Build Institute of America
  • Better Business Bureau
  • Dulles Area Realtors Association
  • Prince William Regional Chamber of Commerce

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Responsible Management Entity

SES is one of only three businesses to be licensed as a Responsible Management Entity. Loudoun County Virginia was the first in the Nation to establish requirements for an RME based on EPA recommendations. SES manages several communities required to have an RME.

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  • Licensed Conventional & Alternative Onsite Soil Evaluators (AOSE)
  • Licensed Conventional and Alternative Onsite Sewage System Operators
  • Licensed Conventional and Alternative Onsite Sewage System Installers
  • NSF Certified Septic System Inspectors
  • Virginia Class A Contractors License
  • Environmental, Monitoring Well and SDS Endorsements
  • Licensed Sewage Handler
  • Licensed Wastewater Treatment Plant Operators
  • Licensed Water System Operators

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