Free Tool
Perc Test Guide and Cost Estimator
A percolation test -- commonly called a perc test -- measures how fast water drains through your soil. It is the single most important factor in determining what type of septic system you can install, or whether your property can support a septic system at all. County health departments require a passing perc test before issuing any septic permit. The test involves digging holes on your property, filling them with water, and measuring the rate at which the water level drops over a set period. That rate, expressed in minutes per inch, dictates everything from drain field size to whether you need an alternative system like a mound or aerobic unit.
Perc Test Cost Estimator
Perc test pricing varies significantly by region and site conditions. Use this estimator to get a ballpark range before contacting a licensed septic engineer.
Perc Rate Interpreter
Already have your perc test results? Enter your rate below to find out what septic system types will work on your property.
Perc Rate Reference Chart
| Rate (min/inch) | Classification | Typical Outcome |
|---|---|---|
| < 1 | Too Fast | Engineered system required |
| 1 - 5 | Excellent | Conventional system approved |
| 5 - 30 | Acceptable | Conventional with proper sizing |
| 30 - 60 | Marginal | Mound or alternative system likely |
| > 60 | Failing | Engineered/aerobic or not buildable |
Thresholds vary by jurisdiction. Some counties set maximum allowable perc rates at 45 or 60 minutes per inch. Always check with your local health department.
Need a perc test done on your property?
A licensed septic engineer will evaluate your soil, conduct the percolation test, and recommend the right system for your site conditions.
Find a Licensed Septic Engineer for Your Perc Test