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Bel Air, MD  21014
410-877-2300

A soil percolation test, often called a “perc test” is a procedure used to measure how quickly water drains through soil at a proposed septic system site, essentially determining the soils ability to absorb wastewater and thus informing the design of the septic drain field needed for a property; it involves digging holes in the ground, filling them with water, and timing how long it takes for the water level to drop, providing crucial data for designing a suitable septic system.

Key points about a soil percolation test:

• Purpose:
  To assess the soil's drainage rate and determine if it can adequately absorb wastewater from a septic tank.
• Process:
  Holes are dug at the proposed drain field location, then filled with water and monitored to see how long it takes for the water level to drop by a specified amount.
• Importance:
  A perc test is crucial before installing a septic system as poor soil drainage can lead to wastewater backup and environmental contamination.
• Factors affecting results:
  Soil type (sandy, loamy, clay), existing water table level, and local regulations.

A wet season perc test is a soil test performed during the wettest season of the year to assess the suitability of a property for an on-site sewage system.
Why perform a wet season perc test?

• Assess groundwater levels
  Wet season perc tests are performed when groundwater levels are highest, usually in February, March, and April. This helps ensure that the septic system will work properly in all seasons.
• Identify restrictive soils
  Some soils may need to be tested during the wet season if they are restrictive.
• Avoid inaccurate assessments
  Wet season perc tests help ensure that the septic system will work properly in all seasons.

When to perform a wet season perc test?

• The wet season perc test period varies by location and year.
• You can contact your local health department to find out when to perform a wet season perc test.

Current Wet Season Memo
Soil Percolation Test Application Procedure
Soil Percolation Test Application
Innovative and Alternative On-Site Sewage Disposal System Consultants
Surveyors List 
Perc Test Update Application 
Soil Chart
Harford County GIS