Perc Testing

When there isn’t any existing municipal sewage systems nearby, that’s when you’ll need to explore the feasibility of a septic system. In order to determine if a conventional system is possible, most county health departments will require a perc test.

In order to design and install a septic or storm water management system, percolation testing, more commonly referred to as perc testing, is required to meet septic system regulations.

A professional perc test may involve multiple holes, different-sized holes, holes with gravel, and other variations. Each jurisdiction has its own laws on perc tests and it is required by DEP and PA rules and regulations.

A perc test is done to determine the soil’s absorption rate for the drainfield size of a new system. This method of soil testing must be performed to ensure the drainfield will be able to accept and drain the incoming water or wastewater properly.

Percolation tests provide the necessary information about the ground you’re building on, and they’re even required by some municipalities. So what is a perc test? Here, we’ll discuss the details.

Every septic system requires an appropriately sized area of suitable soil for effective wastewater treatment. A perc test is a soil test that determines if suitable soil exists on a land parcel.

What is a Perc Test?

A percolation test, perc or perk test, is a procedure performed to review the site drainage in different soils.

It is important for many uses, such as when designing a leach field for a septic system, planning a building design, or considering agricultural use of the land. If the water cannot drain properly, a swamp of sewer water will result. This is a foul-smelling health hazard that could cost you thousands of dollars to correct, or ruin your house or farm entirely.

Traditional septic systems only work if the soil in the leach area is sufficiently permeable, or allows liquids to pass through, that it can readily absorb the liquid effluent flowing into it. Also, there must be at least a few feet of good soil from the bottom of the leach pipes to the rock or impervious hardpan below, or to the water table.

Background of Perc Tests

A percolation test (known as a “perc” or “perk” test) measures the site drainage rate of the soil where a proposed septic system will be installed.

Perc tests are typically done after deep tests are completed. Deep test pit profiles are evaluated to identify restrictive layers such as groundwater, hardpan, and ledge rock.

With this information, it can be determined where the leaching system can be placed and what soil layer is the receiving soil. The perc test is then dug at the depth of the proposed leaching system, or in the case of a fill system where the system is out of the naturally occurring soil the receiving soil layer is perked.

Which Soil Types Allows Water to Drain the Quickest?

The type of native soils factor into your perc test results and where the test should be performed. There are general permeability values for different soils.

Most cities and rural towns have different regulations concerning these soil tests, so keep this in mind when planning for your property. In general, these ranges are used to evaluate soil permeability.

Clean gravel and sand have the most rapid permeability rates, around 1/2 minute per inch. A mix of sand, clay, and gravel is still permeable but not quite as much, around one to three cm/hour. Silt, clay, and stratified clay typically have moderate permeability lower than 1-2 minutes per inch but more than impermeable soil.

What Soils are Perfect for Septic Systems and Drain Fields?

Soil will often pass a perc test when it has high concentrations of sand and gravel.

  • Sandy soils
  • Soils with low clay content
  • Loamy soils
  • Soil with gravel and clay (not too dense or too loose)

What does a Percolation Test Involve?

The soil percolation rate indicates how quickly water moves through soil and helps evaluate the ability of the soil to absorb and treat effluent, or wastewater that has received preliminary treatment in a septic tank.

The percolation rate is measured in minutes per inch (mpi). Soils with slower percolation rates, through which it takes longer for water to travel, need larger drain fields to handle a given amount of wastewater than those with faster percolation rates. Soils with very slow percolation rates may be unsuitable for drain fields.

Local Health Department

Depending on the Health Department’s requirements, the location of the property, the building plans, and the makeup of the soil, a perc test can be very simple and inexpensive, or it can be somewhat complicated and costly.

Contact your local health department official so you are clear on the process and requirements beforehand to ensure there are no hiccups when planning your septic system.

Also remember that, regardless of what you read online, each county health department has an established set of rules and individual requirements that can vary from place to place.

Determining Location

Soil naturally treats and degrades organic matter, destroys pathogens and acts as a filter to remove contaminants from water. Because the soil plays such an important role it’s vital to ensure the selected site can properly handle the water from the distribution laterals.

A septic system works by allowing material from the septic tank to flow into leach lines that are placed adjacent to the tank. As the organic material slowly seeps into the surrounding soil, it is naturally absorbed into the ground and eventually processed through the soil. If the soil surrounding the location of a prospective septic system is not capable of absorbing large amounts of liquid, then a new location will be necessary or the septic system will fail and result in expensive repairs.

In general, tests cannot be conducted in frozen or disturbed soil, and some areas only allow tests during certain months of the year, so plan ahead.

Time of the Year

The time of year can definitely effect perc test results as well as the level of the water table, which is also a concern. In general, the driest season will yield the best results since dry soil readily absorbs water and the water table is at its lowest.

Soil saturated with water from rain or melted snow will not perc well. A site will also fail if the water table is too high. Local septic system inspectors and installers can be a great source of information about local soil conditions and regulations.

Once the location and when to have the perc test conducted are decided, most evaluations start with a deep hole test.

Deep Hole Test

Generally speaking, a deep hole test is used to show the various soils present and their elevations to help find the most suitable location on a particular site for a future septic system.

A deep hole test involves digging through the layers of soil, to find what subterranean conditions exist, and find where the water table is in your area. The cross section of soils are inspected and tested to determine suitability for excavation and construction.

A deep hole test is dug by machine to well below the bottom of the proposed leach field, which is often 7 to 10 feet deep or greater. Soil samples may be taken back to the lab, or visual observations of the soil layers may be sufficient.

Why is a Deep Hole Test Performed?

The deep hole test dug, soil test or observations are used to identify the drainage characteristics of the soil, the seasonal high water table, and the depth of the “limiting zone,” where the soil is unsuitable for treating sewage. The high water table is identified visually by looking for “mottling,” splotches or streaks of color in the soil indicating the occasional presence of water.

Perc Testing for Septic Systems

While most soil experts believe they have enough information at this point to design an effective septic system, most states today also require a percolation or perc test to directly measure the rate at which water percolates through the soil.

The perc test determines how fast water drains into a standard-sized hole in the ground. The results determine whether the town will allow a septic system to be installed, and system designers use the results to size the leach field.

A perc test is conducted by drilling or digging a hole (or multiple holes) in the ground, pouring water into the hole, and then observing the rate at which water percolates, or is absorbed in the soil.

The process is relatively simple and paves the way for a septic system on your property. A perc test is only necessary when the property does not already have access to a municipal sewer system.

Percolation Test Report

In most locations, a perc test report is required to plan a new or renovated septic system, which is included in the price of the test. Once finalized, the report is provided to the local health department and becomes a public record. A perc test report provides standard data such as testing date, location of the test, technician name, and under what conditions the perc test was performed.

A standard perc test report is multiple pages. One page features a graph with times of each reading, water depth, percolation rate, and any comments about the testing process from the examiner. Other pages include a percolation test results table and a scaled drawing of the site plan. The test results table includes columns listing the results of each test. For each test, the table shows the percolation rate, the pre-percolation density, and the post-percolation density. The bottom of the table lists the mean and standard deviation of each test to provide the average results.

At the end of the report, it lists whether the site passed or failed the perc test, and testing requirements vary greatly based on the health department. The test results control whether or not you can build on a given piece of land. Just about any building will require a sewer system unless it has no sinks, toilets, dishwashers, or clothes washing machines.

Perc Test is Successful

You received successful perc test results, what next? A successful standard perc test, in many cases, is the difference between whether your septic or storm water management system will function properly or not. This test can make the difference between a successful, functioning system at inception or a permanently halted project going back to the drawing board for another solution.

Perc Test Failed

A failed perc test means the soil doesn’t drain the water at all or the water doesn’t drain fast enough. The failed perc test can also indicate that water drains too rapidly. Some properties are more likely to have a failed perc test, due to being built on a steep slope.

A property with a low water table has a higher chance of passing it than those with a high water table. A high water table indicates the presence of water in the soil that doesn’t drain properly.

Less commonly, a site can have a failed perc test because the soil is too permeable, allowing the effluent to reach the groundwater before it is fully treated. Very steep slopes are also unsuitable for a conventional leach field.

What happens if you receive your failed perc test results? Even if your site resulted in a failed perc test, all is not lost. Alternative septic systems have become potential options which could include hooking up to municipal sewer systems, or assessing adjoining properties for easements. You would need to work with your county health departments to find out which alternative septic systems are approved for use in your area and which might be suitable for your site.

Start asking some questions to determine what alternative systems might be available…

  • Check with the local county health department about their records of any previous perc tests. Try to determine if they searched the entire property for a proper septic drain field, another section of the property may pass no problem.
  • Can you appeal the results of the previous perc test to the health department, and under what circumstances would the health department reconsider their original determination?
  • If these first steps fail, it may be worth considering an alternative septic system than a traditional septic system. These alternative systems can be a bit more expensive than a conventional option, but they may give you more options to work with. Your health department can inform you of which alternative septic systems are allowed.
  • Soil types vary across any parcel of land. Be sure to try a few places, you might find better results.
  • Also keep in mind that in some areas, if you wait long enough, the municipal water and sewer may become available. If your plan is to buy land and hold it for a while, it could still be worth your while.

Why is a Perc Test Necessary?

Whether you’re purchasing land to build on or updating your current home, a perc test is an essential part of the process to establish site suitability for installing new septic systems. 

A soil and perc tests are necessary when a property does not have access to a municipal sewer system. When there isn’t an existing sewer system nearby, that’s when you’ll need to determine the feasibility of installing a septic and storm system. To decide if a septic system is possible, the county health departments will require a perc test, dependent on your county, rules vary greatly. 

If a septic tank and storm system are placed in soil that can’t properly drain, the consequences can be unpleasant and costly. It is an extremely important step in the property evaluation. 

Soil testing is important before septic systems are installed. It measures the water absorption rate of the soil, determines the ability of the soil to absorb wastewater and predicts the required size for the leach field.  It also analyses the subterranean conditions and the level of water table.

Who Pays for a Perc Test?

In most real estate agent transactions, the buyer will be the one paying for the perc test as part of their due diligence before they close on a purchase. Just as a buyer would pay for a survey, an appraisal, or any other assessment on the property, this cost would typically be paid by the buyer because they need to determine whether the soil is suitable for their intended use.

How Long is a Perc Test Good For?

Each health department has its own rules about how long perc tests are valid. Results are generally valid from two to five years before renewal is needed. At that time, the health department reviews previous perc test results and decides if additional testing is needed. Renewal helps government agencies confirm that the perc test abides by all the current regulations.

The Importance of Testing

As complicated as it might seem, it is extremely important that you go through all the necessary tests and inspections via the right avenues. This will save you time, expenses, and trouble. Taking the time to ensure your property is safe and well-maintained is worth the effort. 

Why Choose Us?

A perc test is a test performed to see how water drains on your property and if it’s suitable for a septic system.

A septic system will help make a property livable if it doesn’t already have water or sewer hookups to a municipal sewage system.

At Delaware Valley Septic, Sewer & Storm, we perform perc testing on any type of soils on any property in Chester, Delaware, and Montgomery County, and have the experience to get it done the right way. Once our test is complete, we can discuss your new septic or storm water installation in greater detail. Call today for an estimate!

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