40 Perc Test Raleigh Nc

What Is a Perc Test? Family Handyman
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Welcome to our blog! Today, we will be discussing an important aspect of property development in Raleigh, North Carolina - the perc test. The perc test, short for percolation test, is a crucial step in determining the suitability of land for septic systems. Whether you're a homeowner looking to build a new house or a developer planning a large-scale project, understanding the perc test process is essential. In this article, we will explore the ins and outs of perc testing in Raleigh, NC, including its purpose, procedure, and significance.

What is a Perc Test?

A perc test, as mentioned earlier, is a percolation test that evaluates the rate at which water is absorbed by the soil on a property. This test is performed to determine if the soil can adequately filter and drain wastewater from a septic system. It helps in assessing the site's suitability for a septic system installation. Essentially, the perc test measures the soil's ability to absorb and disperse the effluent from a septic tank into the ground.

Why is a Perc Test Necessary?

Before constructing a new property or making any modifications that involve wastewater disposal, it is crucial to determine if the soil on the site can support a septic system. A failed or inadequate perc test can indicate soil conditions that are unsuitable for effective wastewater treatment, which can lead to environmental contamination and health hazards. By conducting a perc test, property owners can ensure that their septic systems function properly and do not pose a risk to public health or the environment.

When is a Perc Test Required?

A perc test is typically required in the following situations:

  • Constructing a new residential or commercial property
  • Adding bedrooms or bathrooms to an existing property
  • Replacing an old or failing septic system

In Raleigh, NC, the local health department or the relevant regulatory authority usually mandates perc tests as part of the building permit application process. It is essential to consult the local regulations and guidelines to determine when a perc test is required for your specific project.

The Perc Test Process

The perc test involves several steps and should be conducted by a qualified professional. Here's an overview of the perc test process:

1. Site Evaluation

Prior to conducting the perc test, a site evaluation is performed to assess the property's characteristics, such as soil type, topography, and proximity to water sources. This evaluation helps determine the test locations and provides insights into potential challenges or limitations.

2. Test Hole Digging

Test holes are dug on the property at designated locations. These holes are typically 6 to 12 inches in diameter and 18 to 36 inches deep, depending on local regulations. The number of test holes required may vary based on the property size and local requirements.

3. Water Filling

Once the test holes are ready, they are filled with water and allowed to saturate the soil for at least 24 hours. This step ensures that the soil is adequately soaked and replicates the conditions when the septic system is in use.

4. Water Level Measurement

After the saturation period, the initial water level in each test hole is measured. This measurement serves as a reference for the subsequent calculations.

5. Percolation Measurement

The next step involves measuring the rate at which water drains from the test holes. This is done by adding a specific volume of water to each hole and timing how long it takes for the water to drop a predetermined distance. The percolation rate, also known as the perc rate, is calculated based on this measurement.

6. Data Analysis

Once all the measurements are recorded, the data is analyzed to determine the average perc rate for the site. This information is then compared to local regulations and guidelines to assess the suitability of the site for a septic system.

Interpreting Perc Test Results

After completing the perc test, the results are used to classify the site's suitability for a septic system. The interpretation of perc test results may vary depending on local regulations, but generally, they fall into the following categories:

1. Acceptable

If the perc rate falls within the acceptable range specified by local regulations, the site is deemed suitable for a septic system installation. This means that the soil can adequately absorb and disperse wastewater, minimizing the risk of environmental contamination.

2. Marginal

A marginal perc test result indicates that the soil's percolation rate is slightly below the acceptable range. In such cases, additional measures may be required, such as increasing the size of the drain field or implementing alternative wastewater treatment systems.

3. Failed

A failed perc test result indicates that the soil's percolation rate is significantly below the acceptable range. This means that the soil cannot effectively absorb and disperse wastewater, making the site unsuitable for a conventional septic system. Alternative wastewater treatment options or site modifications may be explored in such situations.

Importance of Perc Testing in Raleigh, NC

Perc testing plays a crucial role in property development in Raleigh, NC, due to the region's specific soil and environmental conditions. Here are some reasons why perc testing is important in Raleigh:

1. Protecting Water Quality

Raleigh, NC, is known for its abundant water resources, including lakes, rivers, and groundwater. Properly functioning septic systems, determined through perc testing, help protect these water sources from contamination by ensuring that wastewater is adequately treated and filtered before reaching them.

2. Complying with Regulations

Local regulations and guidelines in Raleigh, NC, require perc testing to ensure that property owners adhere to the necessary standards for wastewater disposal. Compliance with these regulations is essential to obtain building permits and avoid legal issues in the future.

3. Ensuring Long-Term System Performance

Perc testing helps ensure that septic systems in Raleigh, NC, are installed on suitable soil, allowing for efficient wastewater treatment and preventing system failures. By conducting a perc test, property owners can avoid costly repairs and maintenance associated with failing septic systems.

4. Planning for Future Growth

Perc testing provides valuable information for property developers in Raleigh, NC, who are planning large-scale projects. By understanding the soil's suitability for septic systems, developers can make informed decisions about land use and infrastructure development.


The perc test is a critical step in property development in Raleigh, NC, and understanding its process and significance is essential for homeowners, property developers, and anyone involved in construction projects. By conducting a perc test, individuals can ensure that their septic systems function effectively, protect water quality, and comply with local regulations. Remember to consult with professionals and adhere to local guidelines to ensure a smooth perc testing process and successful property development.