A perc test, or percolation test, is what is done to determine how much water can be absorbed by the soil before a leach field is installed. A septic system cannot be properly designed or installed without this testing being completed first.
When a perc test is completed, the person performing the test checks how quickly a specific amount of water is being absorbed by the soil within a drilled area. This test is always completed the same way, but the results are used differently in many cities and states.
Perc Test Procedure
Performing a perc test is as easy as drilling two or more holes about thirty feet apart. The holes are usually 15 centimeters in diameter and go down 60 or 90 centimeters. Two inches of gravel is placed in the holes and water is added continuously to keep a foot inside the holes.
The next day, six inches of water is added to the holes before checking how much water has disappeared in thirty minutes. The goal is to determine how long it takes for water to drop one inch.
Is Perc testing necessary?
The only time a perc test is necessary is when a septic system needs to be installed. If sewage is installed, there is no need to perform a perc test. However, if there is no sewer and there are no plans for sewage in the future, a perc test will show whether it is safe to install a regular septic system or whether a modified system will be necessary.
Costs of a Perc test
The cost of a perc test depends on where it is being performed, as well as how many holes need to be drilled to do the test itself. The condition of the soil can also play a role, because it can cost more if the soil is difficult to dig.
Currently, the cost of a perc test is typically between one hundred and one thousand dollars. Most of the time this cost is made up of the use of a backhoe plus the person doing the testing. There are times when additional expenses are added to the bill later. These extra expenses may include needing to dig extra holes, digging a deeper hole, or needing to drive further than average to get to the land.
The Perc Test Requirements
Each area seems to have its own requirements when it comes to perc testing. However, key requirements generally include the following:
- Steep Slope – The slope typically cannot be more than twenty to thirty percent.
- Filled Land – It is best to use an area with native soil, but an engineered fill will be considered on a case-by-case basis.
- Wetlands or Flood Zones – Both of these areas are not considered acceptable for leach fields.
- Site Drainage – A leach field should never be placed where there is storm runoff, because the area could turn to nothing or eventually flood and cause even more damage.
Backtracking Requirements for Perc Tests
Again, each area has its own requirements when it comes to leach field mishaps, so it's important to check with your local government before getting a perc test. However, here are the basic setback requirements for leach fields:
- House – 10-20 feet
- Property line – 10 feet
- Private well – 50-100 feet
- Drinking water piping – 25 feet
- Open water – 100 feet
- Dry creek bed – 25 feet
- Basement drains – 25 feet
Alternatives if a Perc test fails
Many people immediately panic if the perc test fails, but it's important to know that there are some alternatives if this happens. Here are some options everyone should consider:
- Check with the Department of Health – It is important to check with the Department of Health to see if there is any record of other perc tests performed on this property. This is important because one section of the property may be better for a leach field than another. If only one section was tested and failed, there may still be another location that will pass with flying colors.
- Appealing the results – There is the possibility for a person to appeal the results of a perc test, but everyone should know that there are only a few circumstances in which the original results will be changed.
- Determine the season in which the Perc test was performed – The soil drainage rate may be different during the rainy season compared to the dry season. Therefore, the time of year may have made a difference in the pass/fail rate.
- Consider a modified septic system – If there is nothing a person can do about perc testing, it may be necessary to install a modified septic system. These systems are a little more expensive, but at least it's an option that will allow you to build on the property.
- Water and sewer may be available in the future – Sometimes people buy land for the future, so a failed perc test is not the end of the world. In this type of scenario, water and sewage may reach the area before construction even begins and then the perc test results will not matter.
When a person wants to purchase land with the intention of building a house or other building, they must have a perc test done before signing the sales papers. The reason for this is that if the perc roll fails and there are no other options, the person may be stuck with land they cannot use. Failure to perform this test can cause many problems in the future, especially if a bad result impedes construction plans.
At least by doing the perc test before the sale, the buyer can back out if the results are not as expected.
No one should skip a perc test because the results can be devastating when it comes to getting approved for a mortgage or being able to use the building that has just been built.
If a person has concerns when it comes to a perc test, they should err on the side of caution and get it done to stay safe. They may never need it, but at least they will know whether their land passes or fails when it comes to installing a septic system.
