What is a PERC Test and Should You Get One in SC? May 27, 2025

If you’re buying land or planning to install a septic system, you’ve probably heard the term “perc test.” But what is a perc test, really—and why should you care? Short for percolation test, this simple but essential evaluation tells you how well water drains into your soil. And in many cases, it determines whether or not you can build your dream home on a given property.

Let’s break it down—what a perc test involves, when it’s required, and how it directly impacts your ability to install a house septic tank or plan for long-term land use.

Understanding the Purpose of a Perc Test

A perc test measures how quickly water can move through your property’s soil. Why does that matter? Because septic systems rely on the ground’s ability to absorb and filter wastewater. If water drains too slowly or too quickly, your land may not support a septic tank drain field, which could delay or even prevent building.

This is why perc testing is a standard step when buying rural or undeveloped property, or when designing a new house septic tank system.

How a Perc Test Works

The process of perc testing is fairly straightforward:

Several small holes are dug in the ground, typically 6 to 12 inches wide and up to 3 feet deep.
These holes are filled with water, and technicians measure how quickly the water level drops.
Results are recorded in minutes per inch, revealing how well the soil can absorb water.

This test helps engineers determine how to design your septic tank test system, especially the septic tank drain field, which is where wastewater gets filtered into the ground.

The Role of Perc Tests in Septic Design

A successful perc test is crucial for planning the size, location, and type of your septic system. The results tell engineers:

Where to place the septic tank drain field (must be on well-draining soil)
How large the system needs to be based on percolation rates and home size
Which type of septic design is needed—standard gravity-fed, mound system, aerobic treatment unit, or others

For example, a slow percolation rate may mean your land can’t handle a traditional drain field, requiring a more advanced or engineered septic solution. On the other hand, a quick rate might necessitate additional filtration to protect groundwater.

Ultimately, perc test results are the blueprint that your septic system designer and installer rely on to meet code, keep your property safe, and avoid system failure.

Do You Need One in South Carolina?

Here’s where things get specific: South Carolina does not require a traditional perc test for septic system permits.

Instead, the Department of Environmental Services(DES) conducts a comprehensive soil evaluation. This includes assessing:

Soil type and composition
Depth to seasonal water table
Drainage characteristics
Site slope and topography

That means while you may not need to arrange for a perc test in South Carolina to meet legal requirements, it can still be incredibly helpful — especially if you’re in the early stages of land evaluation.

When You Need a Perc Test

You’ll want to consider a perc test if:

You’re purchasing land for a new home without public sewer access
You’re replacing an old or failing septic tank
You’re expanding your home with an addition that increases water use
You’ve had issues with existing drainage or soil saturation

In these cases, a perc test can give you advance insight before making big financial commitments.

When a Perc Test Still Makes Sense

Even in South Carolina, there are plenty of scenarios where a perc test can be helpful:

You’re buying land and want to ensure it will support a septic system
You’re adding a guest house, workshop, or other outbuilding that increases water usage
You’re looking to verify or compare multiple building sites on the same property
You’re investing in property near waterways, wetlands, or areas with high water tables

Performing a perc test voluntarily can help you avoid surprises later — even if it’s not a regulatory requirement.

What Happens If Your Land Fails?

Failing a perc test doesn’t mean you can’t build — but it might mean you need to adjust your plans. Solutions can include:

Moving the septic tank drain field to a better area
Installing an engineered or alternative septic system
Improving the soil or using raised-bed systems

Your local health department or a licensed septic professional can guide your next steps.

How to Prepare

Before testing, clear brush or debris from the site. Ensure that the land is not waterlogged or frozen, and that access is available for equipment or inspectors. Check with your local environmental agency or county office to understand site requirements and whether previous land use might affect the results.

How Long Is a Perc Test Valid?

Most perc tests are valid for 1 to 5 years, but this depends on your location and any changes made to the land. If significant grading or construction has occurred, a new test may be necessary.

What is a Perk Test? (And Is It Different?)

You may have heard both “perc test” and “perk test” used interchangeably. Good news: they mean the same thing. “Perc” is short for “percolation,” but some people pronounce it “perk.” No matter what you call it, the purpose is the same — to determine if your soil is suitable for a septic system.

The Role of Soil Tests

In many cases, a perc test is done alongside a broader soil test, which evaluates:

Soil composition and texture
Compaction and structure
Depth to bedrock or groundwater

Together, they give a complete picture of how your property will handle wastewater disposal.

What This Means for You

So, what is a perc test, and how does it affect you? In short, it’s a gatekeeper for land development and septic system planning. Whether you’re buying your first plot of land, replacing a failing septic tank, or designing a custom home, perc testing provides peace of mind.

While South Carolina does not require traditional perc tests for permits, they’re still a smart move when evaluating property. Pairing a perc test with a professional soil evaluation helps you make informed decisions and avoid future headaches.

How WeCo Rooter Can Help

Even though South Carolina doesn’t require traditional perc testing, WeCo Rooter understands the value of thorough site evaluation. Our licensed team offers expert guidance for:

Coordinating soil evaluations required by DES
Recommending when a perc test may still be beneficial
Troubleshooting failed drain fields or planning system upgrades
Helping you choose the right septic system for your land and water use needs

We’re proud to serve homeowners and buyers across South Carolina with dependable, clear, and friendly support. Not sure where to start? Contact WeCo Rooter today, and we’ll walk you through the process.