A perc test is a soils test completed to determine if the soil and groundwater conditions on a property are suitable for installation of an onsite sewage disposal system. All properties not served by public sewer must have this test before beginning construction of any structure with plumbing. If an acceptable area is found, a surveyed plat is submitted for review to establish an area solely designated for sewage disposal. Perc tests are performed when contemplating new construction, adding on to land already served by on-site systems, and when a system fails.

SMCHD’s Environmental Health Division conducts site evaluations for the construction of residential and commercial onsite sewage disposal systems. Effective July 1, 2025, the application for a new construction perc test will be available through the SMCHD website and requires a fee. Perc test applications and fees will no longer be accepted at the Department of Land Use and Growth Management beginning July 1, 2025. The perc test application will also be available to be emailed or mailed upon request by either calling or emailing the Division of Environmental Health’s Administrative Office at 301-475-4321 or smchd.env@maryland.gov. In cases where the septic system for an existing house fails, the health department receives applications for repair perc tests; there is no fee associated with this service.