If you're building a new home or buying vacant land in an area without municipal sewer service, one of the earliest and most important steps happens before a single shovel touches the ground: testing whether the soil can actually support a septic system. That test, commonly called a perc test, determines what kind of system a property can have, and in some cases, whether it can be built on at all.
What Is a Perc Test?
A percolation test, or "perc test," measures how quickly soil absorbs water. It's performed by digging a series of test holes in the area of the proposed drain field, presoaking them, filling them with water, and timing how fast the water level drops. The result is expressed in minutes per inch, a rate that tells engineers and health officials how well that specific soil can accept and treat wastewater.
Sandy, well-drained soil tends to absorb water quickly, while denser, clay-like soil absorbs it much more slowly. That absorption rate, combined with a broader soil evaluation, is what determines how a septic system on that property needs to be designed, and how large the drain field needs to be to handle the home's wastewater.
How This Fits Into Livingston County's Process
In Livingston County, soil evaluation is a required step before any septic permit can be issued, and it goes beyond a perc test alone. A specialist from the county's Environmental Health Division digs test borings, typically to a minimum of 8 feet and sometimes as deep as 20 feet, to confirm there's a consistent layer of naturally occurring, permeable soil within a set depth of the surface. Two borings, spaced at least 50 feet apart, must meet the county's criteria. The evaluation also checks for signs of a seasonal high water table, since soil that's regularly saturated can't treat wastewater effectively no matter how well it otherwise drains.
If a property's soil and water table conditions meet the standard, a conventional septic system can typically be designed and permitted. If they don't, the county may require an alternative system design, such as a pressure mound, engineered to work around less favorable conditions. In some cases, a site's soil or water table may not support a septic system at all. This is exactly why testing early, before finalizing house plans or a land purchase, matters so much.
From Soil Test to Installed System
For new construction, a septic system typically moves through several stages:
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Site evaluation. A specialist assesses the property, including its layout and distance from wells, water bodies, and structures, to get a sense of where a system could be located.
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Soil and percolation testing. Test borings and a perc test determine the depth to suitable soil, the presence of a seasonal high water table, and the water absorption rate in the proposed drain field area.
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System design. Based on the soil results, the number of bedrooms or expected household size, and site constraints, a system is sized and designed, whether that's a standard conventional system or an engineered alternative.
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Permit application. The design and supporting documentation are submitted to the county for review and approval before any installation can begin.
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Installation. Once permitted, a contractor installs the tank, drain field, and associated components according to the approved design.
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Inspection and approval. The completed system is inspected before it's covered and put into service, confirming it was installed according to the approved plan.
Timelines vary by property and by how quickly permits move through the county, so it's worth building some flexibility into a construction schedule around this process.
Why This Matters Before You Buy or Build
Soil and water table conditions can vary significantly from one property to the next, even within the same neighborhood. A perc test and soil evaluation are the only way to know, with any certainty, what a specific piece of land can support. Skipping this step, or assuming a property will pass because a nearby lot did, is a common way that land purchases and construction budgets run into costly surprises later. Getting a soil evaluation done as early as possible, ideally before a land purchase is finalized, gives you the clearest picture of what's realistic to build and what it may take to make a septic system work on that site.
Planning a new build or eyeing a piece of land in Livingston County? A soil evaluation early in the process can save you time, money, and a lot of guesswork later on. Patrick Esper Septic and Excavating is a licensed, insured septic company based right here in the area. Contact us today to talk through what your property might need.