Planning to build on a piece of rural property? Most probably, the area will not have access to a municipal sewage system. That’s when you’ll need a percolation test or a perc test to go ahead with the construction. Learn all about this type of soil test, and how much does a perc test costs, in this article. 

A perc test is one of the most common tests undertaken by home builders who have to build on a new plot of land. It is through this soil test that you get the necessary information about the ground you’re building on. Most municipalities mandate such a type of evaluation. 

What is a percolation test?

A perc test aka soil and site evaluation is a way to assess the physical properties of a particular land in terms of its soil, landscape, and site features. A perc test determines the suitability of a parcel of land to site a septic system.

Basically, a percolation test or a perk test, evaluates how well a soil absorbs liquid. It can also be used to determine which type of vegetation will grow well on a specific site. But, that’s a secondary function. The main one being checking a soil’s suitability.  

In most areas, a home builder is required to get a permit before installing a new septic tank or a drainage system (such as French drains). And this is dependent on the soil absorption rate or the percolation rate — which should be within the specified range. 

Perc test cost

percolation test

A perc test usually costs $750 to $1,850 with most builders spending $1,300 on average. However, keep in mind that the cost of perc test could go as high as $3,000 depending on the local regulation and the size of the leach field. Or, the required infiltration basin. A standard percolation testing costs only $150 to $300. But, it’s a very basic test that evaluates a hand-dug hole and that too without professional tools.

Keep in mind that the perc test cost can vary to a large extent based on the total acreage of land, site location, the number of perc sites, site vegetation, and landscape design. For example, a perc test for a 1-acre site begins at $600.

To give you a better idea, here are some approximate perc test costs according to the different land sizes:

  • 0.25 Acre: $150 – $250
  • 0.50 Acre: $300 – $500
  • 0.75 Acre: $450 – $750
  • 1 Acre: $600 – $900
  • 2 Acres: $900 – $1,400
  • 5 Acres: $1,100 – $2,000

Other factors that determine the perc test pricing 

Percolation testing costs tend to be highest when:

  • A licensed engineer or soil scientist performs perc tests.
  • The testing uses excavation equipment.
  • There’s a requirement for multiple perc test holes or test pits — as in the case of a professional perc test.
  • Site access is a little difficult or steep.
  • There’s a mix of different types of soils such as wet, rocky, or dense soils. Sandy soils tend to be more permeable as compared to heavy clay soils.
  • The site location is in a highly regulated area with high building costs.

Why a perc test?

A percolation test measures water absorption. Only after passing the soil test, can a builder get the required permit. And, only then can they properly design an adequate septic system for the site. 

Therefore, it’s important to determine the percolation rate of the surrounding land before installing a septic system. Or else, the septic system could flood in due course or pollute the groundwater.

If the soil on a piece of land fails the perc test, it means that it’s unable to handle liquids within the required percolation range. That means it’s unsafe to install a septic system there. For a failed perc test, you won’t get approval from the local health department.

Another reason for conducting a perc test is that it measures potential flood risk in areas where there’s a large deposit of water onto the land, either by nature or through planning. 

How is it done?

If you want to request a perc test, you’ll have to contact your local health or environmental agencies. They will inform you if the test has to be done by a government agent or you can hire an independent engineer for the test procedure. 

Usually, an engineer discusses the site preparation and decides through a land survey where the holes should be dug. You’ll have to factor in the extra cost of the land survey. 

In a simple perc test, an inspector or engineer digs holes to a specific depth, pre-soaks the multiple holes and fills them with water to a predetermined, measurable level. The experts then measure the sinking water levels for a certain length of time. Basically, they measure the amount of time it takes for the water to absorb into the soil.

Keep in mind that septic systems require a minimum percolation rate of around 60 minutes per inch and a maximum percolation rate of 150 minutes per square inch. This means that the water should drop one inch in 60 minutes to one inch in 150 minutes.

If it’s found that the ground isn’t permeable enough, the septic system’s drain field will drain too slowly. Or, if the soil is too permeable, it would pose a pollution risk. The effluence from the septic tank may get absorbed into the groundwater.

Read more: Where are the best places to search for cheap land?

How can I do a perk test myself?

diy perc test

If you only need a perc test for gardening or landscaping purposes, you can manage a simple perc test as a DIY project. All you need is a shovel and tape measure. A licensed landscaper or a gardener may be able to help you with the test. They might charge $25 to $100 depending on how many holes are dug and the time taken.

Perc test permit

Keep in mind that each jurisdiction has its own laws regarding perc tests. Some areas require a traditional perc test while others specify a deep hole test or a seasonal high water table test. If an official perc test deems that your land meets all local requirements for a septic or drainage system, you can apply for the requisite permit. A drainage system permit can cost $100 to $1,000 — depending on the site size and its conditions. 

How long is a percolation test good for?

Every local health department has its own rules and regulations regarding the length of time for which perc tests are valid. Generally, perc test results are valid for two to five years after which you’ll need a renewal. 

Before renewing your septic permit, the department of health decides if additional testing is needed based on the previous test results. It’s how the government agencies ensure that all the perc tests abide by the current regulations.

Generally, a soil evaluation conducted by a licensed soil scientist does not expire unless the drain field and its soil conditions physically change.

Key takeaway

Perc tests and their requirements vary widely from one place to another. It’s best to contact your county health department if you’re planning to request such a test. You can find out all the local laws and regulations. That way, you’ll not run into any roadblocks before a septic installation.

Read more: A complete guide on home sewer maintenance

How much does a perc test cost, on average? was last modified: October 15th, 2021 by Ramona Sinha
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