# Perc Test: What It Is, How It Works, and What It Costs | FOUND A perc test shows whether soil can treat septic wastewater. How North Carolina evaluates a site, why lots pass or fail, and what drives the cost of the test. Canonical: https://lotsfound.com/insights/perc-test/ ## Perc test: what it is and what it costs A perc test is the soil and site evaluation that decides whether a lot can use a septic system. In North Carolina, county environmental health or a licensed soil scientist performs it, and the result sets what the land can hold. ## What a perc test is A perc test is an evaluation that shows whether the soil on a lot can absorb and treat wastewater from a septic system. The name comes from the older percolation method, which times how fast water drains from a hole. Many places now read the soil itself instead. ## Why septic approval depends on it Septic approval depends on the perc test because the soil does the treatment. The drainfield releases liquid into the ground, and the soil cleans it as it moves down. Soil that drains too fast passes untreated water to groundwater. Soil that drains too slowly, or sits wet part of the year, pushes it to the surface. No septic permit issues until the soil and the site pass. ## How North Carolina evaluates a site North Carolina evaluates a site by examining the soil and the site, not by timing water in a hole. County environmental health staff perform the evaluation under state rules. State law also lets licensed soil scientists perform evaluations under set conditions. The evaluator digs pits or bores, reads the soil layers, and walks the lot. A passing evaluation leads to an improvement permit, and a construction authorization follows before installation. County environmental health confirms the steps for a given lot. ## What makes a site pass or fail A site passes when the soil can treat wastewater and the lot has room for the system and a repair area. Evaluators read these factors. - **Soil texture.** Sandy soils drain fast, heavy clays drain slowly, and soil structure changes how water moves through both. - **Depth to rock.** Shallow rock or a dense layer leaves too little soil to treat the water. - **Depth to the water table.** Gray or mottled soil colors show where water sits part of the year, even in a dry season. - **Slope.** Steep ground, drainageways, and low spots limit where a drainfield fits. - **Repair area.** The lot needs usable soil for the first system and space for a replacement. Setbacks from wells, streams, and property lines shrink the area that counts. ## What drives perc test cost Perc test cost depends on who performs the work, how many lots need it, and how hard the site is to read. - **The evaluator.** County fees and private soil scientist fees are set differently. - **Lot count.** A subdivision needs an evaluation for each lot. - **Site access.** Wooded or wet ground can need clearing first. - **Soil complexity.** Marginal soils take more pits and sometimes a second visit. - **System design.** A lot that needs an engineered system adds design and review. ## What the public record shows The public record shows soil types and their septic ratings at survey level, and sometimes the permits for existing systems. The USDA soil survey flags wet soils, shallow rock, and slope. The record cannot show whether a given lot passes, because soils change inside a single mapped area. A licensed soil scientist or county environmental health answers that. See what we check on [flood, wetlands, and soils](/what-we-check/flood-wetlands-soils/) and on [water and sewer](/what-we-check/water-and-sewer/). ## What it means for land Septic suitability sets the lot count on land that sewer does not reach. Two tracts with the same zoning can hold different numbers of homes. Compare the options in [sewer, septic, or a package plant](/insights/sewer-septic-or-package-plant/), then see [how many houses per acre](/insights/how-many-houses-per-acre/) a tract can hold. ## Questions ### How much does a perc test cost? The cost varies by county, by evaluator, and by site. Ask county environmental health for its fee schedule, and ask a licensed soil scientist for a quote on the specific lot. ### Is a perc test the same as a soil evaluation? In North Carolina, the soil and site evaluation does the job a perc test does elsewhere. People use both names for the step that decides septic approval. ### Can a lot that fails a perc test still get a septic system? Sometimes. An engineered or alternative system can work where a conventional system cannot. Some lots fail for every system type. County environmental health and a licensed soil scientist tell you which case applies. Transactions are handled through a licensed North Carolina real estate brokerage.