Decoding Perc Tests: Knowledge For Every Land Buyer | askBAMLand

As a land buyer, there are many factors to consider when purchasing a property. One of the most important considerations is effective waterwater management.

Perc tests evaluate the soil's ability to absorb and disperse wastewater from a septic system. These tests are conducted to assess whether the soil can support a septic system and comply with regulatory requirements.

In this article, I will provide considerations for land buyers, the role of the seller, financial considerations, and legal and zonal considerations. With this information, you can make an informed decision when purchasing land and ensure that you are compliant with all regulations and requirements.

Key Takeaways

  • Effective water management is a critical consideration when purchasing land.
  • Perc tests are used to determine the suitability of the land for installing a septic system.
  • Compliance with local, state, and federal regulations and requirements is essential.
  • Seeking professional assistance can save time, money, and potential headaches.

Table of Contents

Understanding Perc Tests

As a land buyer, understanding perc tests is essential to determine the suitability of the land for installing a septic system.

A perc test, also known as a percolation test, evaluates the soil's ability to absorb and filter wastewater effectively. It involves measuring the percolation rates, which is the rate at which water drains through the soil on your land, in minutes per inch (mpi).

During a perc test, a hole or multiple holes are dug in the ground and filled with water. The time it takes for the water to percolate, or be absorbed in the soil, is measured, and the results are used to calculate the soil's percolation rate. This percolation rate is then compared to the local regulations to determine if the land is suitable for a septic system.

Regulations and Requirements

If you want to install a septic system, there are various regulations and requirements that you need to comply with. These regulations are usually set by the local or county health department, and failing to comply with them can result in hefty fines or even legal action.

Local Municipal Regulations

Before purchasing land, it is important to research the local regulations and requirements for your municipal sewage system.

This can include setback requirements, easements, and zoning regulations. These regulations can vary from one location to another, so it is important to ensure that you are familiar with the specific regulations in your area.

State and Federal Regulations

In addition to local regulations, there are also state and federal regulations that you need to comply with. These regulations can include requirements for soil testing, percolation rates, and the size and type of septic system that can be installed.

Professional Septic Installation

To ensure compliance with all regulations and requirements, it is important to work closely with a qualified septic system installer. They will be able to guide you through the process and ensure that your system is installed in compliance with all regulations.

Conducting a Perc Test

When buying land, it's important to conduct an initial perc test  to determine the soil's ability to absorb and disperse wastewater from a septic system. Here's what you need to know about conducting a perc test:

Access to the Site

Before conducting a perc test, make sure you have access to the site. This may require obtaining permission from the landowner or coordinating with a real estate agent.

Time of Year

It's important to conduct a perc test during the right time of year. In general, it's best to conduct the test when the soil is moist, which is typically in the spring or fall. Avoid conducting the test during periods of heavy rain or drought.


When selecting a location for the perc test, consider the location of the septic system and the topography of the land. The test should be conducted in an area where the septic system will be located and where the soil is representative of the entire site.

Soil Testing

A perc test can be used to help you measure how water passes through your soil. The time it takes for the water to drain is measured and used to determine the soil's ability to absorb and disperse wastewater.

Deep Hole Test

In addition to the perc test, a deep hole test may also be conducted to evaluate the soil's suitability for a septic system. This involves digging a deeper hole and visually inspecting the soil for signs of compaction or other issues that could impact the system's performance.

Soil Evaluation

Once the perc test and deep hole test have been completed, the soil is evaluated to determine its suitability for a septic system.

This evaluation takes into account factors such as the soil type, depth to groundwater, and the site's topography.


It's important to work with a licensed excavator or engineer when conducting a perc test. This ensures that the test is conducted properly and that the results are accurate. Additionally, many local health departments require oversight of perc tests and septic system installations.


After the perc test has been completed and the soil has been evaluated, a survey may be conducted to determine the exact location of the septic system on the property.

This survey ensures that the system is installed in the correct location and meets all local regulations.

Interpreting Perc Test Results

Percolation Rate

When it comes to understanding perc test results, there are a few key factors to consider. First and foremost, the percolation rate of the soil is a critical component of the test.

The percolation rate will help you understand how well your soil holds and filters out wastewater.

Soil Permeability

Additionally, soil permeability is another crucial factor to keep in mind when interpreting perc test results.

Soil permeability refers to how easily water can move through the soil. In general, soils with higher permeability rates are better suited for septic systems, as they can more effectively filter and absorb wastewater.

Failed Tests

It's also essential to understand that a failed perc test can have significant implications for land buyers.

If a site fails the perc test, it means that no house can be built on the land until the issue is resolved. As a result, it's important to make any offer to purchase land contingent on the site passing the soil and perc tests. Perc test cost can be upwards of $750 to $2,000, so you want to avoid failed tests!

Overall, interpreting perc test results requires an understanding of various factors such as soil type, depth to groundwater, and local regulations. These factors can significantly influence the absorption rate of the soil and ultimately determine whether it meets the requirements for a conventional septic system installation.

Professional Assistance

When it comes to perc tests, it's always better to seek professional assistance. As a land buyer, you want to make sure that you're making an informed decision, and that's where licensed professionals come in.


An engineer or licensed excavator can perform the perc test and provide you with accurate results. They can also advise you on the type of septic system that would work best for your property based on the test results.

Real Estate Agents

In addition to licensed professionals, a real estate agent can also be a valuable asset. They can provide you with information about the area and any potential issues that may arise with the property. A lawyer can also be helpful in reviewing any legal documents related to the property and ensuring that everything is in order.

Overall, seeking professional assistance can save you time, money, and potential headaches down the road. It's always better to be cautious and informed when making such a significant investment.

Considerations for Land Buyers

When buying land, it's important to consider several factors that can affect the suitability of the property for building and development. Here are some of the key considerations that every land buyer should keep in mind:

Water Table and Groundwater

Understanding the water table and groundwater levels is crucial when buying land. If the water table is too high, it can cause problems for building foundations and septic systems.

Additionally, groundwater contamination can be a serious health hazard. It's important to consult with a professional to assess the water table and groundwater levels before purchasing land.

Buildable Property

Not all land is created equal. Some properties may not be suitable for building due to zoning restrictions, environmental regulations, or other factors. Before purchasing land, it's important to ensure that it is designated as "buildable" by the local authorities.

Wetlands and Flooding

Wetlands and floodplains can pose significant challenges for land development. These areas are often protected by environmental regulations, and building on them can be difficult or impossible.

It's important to have a thorough understanding of the wetlands and floodplains on a property before making any purchase decisions.


Erosion can be a serious problem for land development, particularly on steep slopes or in areas with heavy rainfall. It's important to assess the risk of erosion on a property before purchasing it, and to take steps to prevent erosion during the building process.

Seasonal High Water Table

In some areas, the water table can rise significantly during certain times of the year. This can cause problems for building foundations and septic systems. It's important to assess the risk of a seasonal high water table before purchasing land, and to take steps to mitigate any potential issues.

Land Perc Test

One of the most important considerations for land buyers is the results of the land perc test.

This test assesses the soil's ability to absorb and filter wastewater effectively, and is essential for determining the feasibility of installing a septic tank. It's important to understand the results of the perc test before making any purchase decisions.


The topography of a property can have a significant impact on its suitability for building and development. Steep slopes, rocky terrain, and other factors can make building difficult or impossible. It's important to assess the topography of a property before making any purchase decisions.

As a land investor, I always make sure to thoroughly assess these factors before purchasing any property. By taking the time to understand these considerations, I can ensure that I'm making a wise investment in a buildable property that will provide a solid return on my investment.

Perc Tests for the Most Accurate Results

As someone who has experience in land buying, I know how important it is to conduct perc tests before making a purchase. If you are asking yourself ‘What is a perc test?’, what is equally important to consider is the accuracy of any perc test you evaluate.

However, there are different methods for conducting these tests, and I was curious to know which one is the most accurate. After conducting some research, I found that hydraulic perc tests are generally considered the most accurate method for determining soil permeability.

Hydraulic Perc Tests

One study conducted by the University of Wisconsin-Madison found that hydraulic perc tests were able to accurately predict soil permeability in a variety of soil types, including sandy, loamy, and clay soils.

The study also found that hydraulic perc tests were less affected by variations in soil moisture content compared to other methods, such as manual perc tests or electronic perc tests.

Overall, if you're looking to buy land and want to ensure that you have accurate information about soil permeability, it's worth investing in a hydraulic perc test. While it may be more expensive to use a hydraulic test in test holes than other methods, the accuracy and reliability of the results can help you make more informed decisions about land use and development.


Brittany Melling

Brittany Melling

Brittany has been in the land business since 2020 when the world was starting to shut down. Since then, we’ve sold to dozens of people from ATV weekend warriors to camping enthusiasts to retired truck drivers. Our inventory spans mostly in the western United States. We’ve been trained by experience, land acquisition courses, and hundreds of hours meeting with county assessors and clerks, zoning officials, realtors, and land investors. We’ve answered hundreds of questions from people regarding the buying and use of land.

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