What is a Perc Test?
A perc test (percolation test) measures how quickly water drains through soil on a property. It is required for properties that will use a septic system (properties not connected to municipal sewer). The test determines whether the soil can adequately absorb and filter wastewater from a septic system, and if so, what type and size of septic system is appropriate.
How a perc test works
A licensed professional digs test holes at the proposed septic system location, fills them with water, and measures how quickly the water level drops. The results are expressed in minutes per inch (MPI). Most jurisdictions require a percolation rate between 1 and 60 MPI. Too fast (less than 1 MPI) means the soil does not filter waste adequately. Too slow (more than 60 MPI) means the soil cannot absorb enough water.
Why perc tests matter for investors
A failed perc test on a property without municipal sewer access can make the property unbuildable or significantly reduce its value. If you are buying raw land or a property with a failing septic system, a perc test determines whether a new system can be installed. Failed perc tests may require expensive alternative systems (mound systems, aerobic treatment units) that cost $15,000-$30,000+ compared to $5,000-$10,000 for a conventional system.
Perc test and property value
Land with a passing perc test is significantly more valuable than land without one. In rural areas where septic is the only option, a perc test is essentially a certificate of buildability. When wholesaling raw land or rural properties, a passing perc test is a major selling point and should be highlighted in your marketing materials.
Cost and timing
A perc test typically costs $500-$1,500 depending on the jurisdiction and the number of test holes required. Some jurisdictions only allow testing during certain seasons when soil moisture is representative. Results are provided by the local health department or environmental agency.