When you do your due diligence before buying a property, one must-have element of that process is a perc test (also known as a percolation test).
A perc test determines the water absorption rate of the soil (or the percolation rate).
This test is essential to understanding whether a septic system can be installed.
In short, if land is rural and a municipal sewer system isn’t available, a septic system helps make a property “livable.”
For those who purchase land intending to use it for building or living, a perc test is a must.
Read on to understand not only how this process works, but whether it may disqualify a parcel of land you wish to buy.
1. A perc test tests the rate at which water drains through the soil
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.
This test is normally performed by a licensed excavator or engineer, but has much oversight by your local health department.
Depending on what type of soil your property has, it may or may not easily pass this test.
In #6, we’ll talk more about the soil criteria that gives your property the best chance of passing.
2. A perc test is only necessary if a property doesn’t have access to a municipal sewer system
A perc test, which paves the way for a septic system on your property, is only necessary when the property does not already have access to a municipal sewer system.
So, you should keep this in mind while you’re doing your due diligence because it may eliminate the need for a perc test altogether.
You’ll want to check and see if the vacant land is within reach of an existing sewer hookup.
If it is, then no need to install a septic system.
If not, you will need a perc test as this test ensures that you can install a septic tank.
Most county health departments will require the perc test results to determine if the property is suitable for the system.
Don’t just assume you can go ahead and install one!
If you’re looking to skip out on a perc test altogether, look for properties with existing sewer hookups when you’re shopping for land.
3. Be sure to check with the county’s health department
If you already know you’re ready to hire a licensed engineer to evaluate your property, then all you have to do is Google your county’s name and “health department” to find their phone number.
You’ll want to give the health department a call so you are clear on the process and requirements beforehand to ensure there are no hiccups.
Also remember that, regardless of what you read online, each county has its own individual requirements that can vary from place to place.
Be sure to yield to whatever your health department says.
In most cases, that means you’ll need a health department official present at your perc test so be sure to arrange for this before having the excavator come out.
4. A failed perc test will complicate your plans to build
Alright, so you already know that a perc test is necessary to install a septic system, and most landowners aren’t going to install a septic system if a municipal sewage system is an option.
Yet, what happens if you fail that perc test and no septic system can be installed?
Many landowners encounter this problem.
While you may find the “perfect” land parcel, if it doesn’t pass the soil and perc tests required by county health departments, then it, unfortunately, will be difficult to build on.
This is especially common for rural parcels of land.
As tempting as it may be to purchase the land anyway and try to make something work, you have to think of the worst-case scenario.
If you know the soil won’t work for a septic system before purchasing, then you should avoid purchasing the lot unless you only want to use it for recreational purposes or you fully understand the potential complications (see below).
5. Don’t panic if your land fails a perc test
You purchase land that has failed a perc test.
You know that means it isn’t buildable.
What do you do?
Do you try and sell it?
Do you just leave it?
Is it a lost cause?
What do you do?
The first step is don’t panic.
Just because your property failed a perc test doesn’t mean you can’t build anything on it.
Sometimes you can get around this issue if you’re willing to spend more money on an engineered system or a raised sand bed to help resolve the drainage issue.
In most cases, it depends on what your local health department will allow.
Here are some alternative routes you can try if your perc test failed.
You’ll never know what’s possible until you start asking.
Check with the health department to see if other perc tests have been done
Checking records of previous perc tests can sometimes make all the difference.
While you may have had a perc test done in one area of the property, a previous owner may have had it done in another.
Depending on the size of the property, there may be an area that actually is suitable for a proper septic drain field.
However, if you’re not testing that section, then you’ll continue to fail.
Look into the records and make sure you’re being thorough.
Just because you had one failed perc test doesn’t mean you’ve failed entirely, or the land is a lost cause.
Ask the health department to reconsider
This often feels like a long shot to people, but you’ll never know until you try.
Ask your local health department if you can appeal the results of your previous perc test, or under what circumstances they would reconsider their original determination.
This will get you closer to understanding if it’s actually a “no” or if you can take certain steps on your property to make it more buildable.
Find out what time of year the failed perc test was performed
You’re more likely to pass a perc test if the water table is low, and in many areas, the water table is more likely to be low in certain seasons.
If you know this to be true, scheduling a perc test at an advantageous time of the year can make all the difference.
Find out when the failed perc test was performed, and if it was when the water level would be high in your area, then you may just have a second chance on your hands.
Consider a modified septic system
There are alternative septic systems that can be reasonably priced (depending on your property’s situation and local requirements) and environmentally friendly.
Often, these systems are more expensive than either a traditional septic system or a municipal sewer.
However, if it makes an otherwise unbuildable property buildable again then it might just be worth it.
Have your excavator try a few different places
The topography of the lot can make a big difference in the different types of soil that are present on your land.
And even if you don’t have vastly different topography, you can still have different types of soil sprinkled throughout.
Have your excavator try some different spots on your land to make sure you’re not giving up too soon.
Wait it out
Did you try all of the above to no avail?
Sometimes, if you wait long enough, municipal water and sewer become available in your area.
It can be a long and frustrating waiting game, but it could be worth your while.
If it’s the perfect piece of land, just wait it out!
6. The type of soil your property has plays a large role in whether or not it passes
Soil will often pass a perc test when it has high concentrations of sand and gravel.
This is because sandy soil absorbs water at a much faster rate than clay, silt, or solid rock.
It also does a better job absorbing water when the property is situated in an area with a low water table.
Generally, soil will fall in the middle with any of the following…
Sand and gravel particles
Small silt particles
Miniscule clay particles (the smallest)
7. You can do a few tests on your own soil to see what you have
You can get a rough idea of your soil’s texture before you invest the time and money in a perc test.
Here are a few ways you can do it.
Dig below the top few inches of topsoil, also known as loam, to the lighter soil beneath.
Grab a handful.
If the soil has a sticky, damp texture, and you can form it into a long, thin, ribbon or worm that holds its shape, then it has a significant clay texture.
If you’re able to form a ribbon of soil that is 2 inches or longer, this is called the ribbon test.
It indicates that the soil has a high clay content and may fail a standard perc test.
You can also use this Home Soil Percolation Test.
8. The perc test procedure varies based on the municipality
Ultimately, the perc test procedure varies based on where you are.
However, in most jurisdictions, a perc test will be performed by a licensed excavator.
A county health department official will also be present during the test along with the owner.
The excavator will typically dig two deep holes to test the drainage rate of the soil on-site.
The process is easy – water is poured through the hole they dug, and they time how long it takes to drain in minutes per inch.
The local health department determines and enforces the rules that govern whether your property is suitable for a septic system.
Thus, you usually must have an official present so they can observe the test.
9. A perc test does not last forever
Perc tests are typically good for 2-5 years, although the exact amount of time depends on the local jurisdiction.
Thus, it’s important to know when the last perc test was done.
If it is an older test, you will need to commission a new test if you want to build on the lot.
10. There are some common limiting factors for septic systems beyond a perc test
Even if you pass a perc test, you may not be out of the woods.
Did you know that most municipalities require that a leach field (also known as a septic tank drain field) meet specific requirements above and beyond just a perc test?
We bet you didn’t know that prepping land for building could be so difficult!
Here are some of the things you should know even before you get into the nitty-gritty of septic system regulations.
Steep slope: For a conventional system, the maximum allowable slope is between 20 to 30 percent.
Filled land: Typically, native soils are required. Engineered fill may be acceptable in some cases. Check with local codes.
Wetlands or flood zones: You cannot use wetlands or flood zones for a septic tank drain field.
Site drainage: Your septic tank drain field should not be in the path of runoff during storms. This could cause erosion or flooding of the system.
11. There is a minimum distance required for a septic tank
There are minimum distances that are required from the septic tank and septic tank drain field to buildings, property lines, water pipes, wells, and open water.
The exact distances will vary from jurisdiction to jurisdiction, but typically the most important requirement to keep in mind is the minimum distance between the proposed leach field and any private well (which is usually around 100 feet).
You’ll need to know these distances so that you can abide by the local codes, and you may be asked to find a replacement field to use in 20-30 years when the original field is exhausted.
12. A perc test costs between $750 to $1,850
Just like everything in life, a perc test is going to cost you something, and that cost can be quite a range depending on who you hire and how much work is required.
Keep in mind that $1,850 is on the high end, so you don’t have to be super intimidated by that number.
13. You can use context clues if you want to avoid a perc test
Again, while it’s often recommended to have a perc test done before purchasing a property, we understand if you’re trying to stay on budget.
Fortunately, there are some easily observable factors that can help indicate whether your property will likely pass a perc test.
Don’t want to pay?
Use the context clues!
Look at your neighbors.
Are there houses on their properties?
Does it appear that they passed a perc test?
If that’s the case, there’s probably a pretty good chance that you’d pass it as well.
While there’s no guarantee, if you’re willing to take that risk then there is a decent chance.
Check for bodies of water nearby.
A nearby body of water could mean many things: water is close to the surface, wetlands, or a flood zone.
While these aren’t always correlated with your property’s ability to percolate, there’s more of a chance that there could be a problem.
In this case, it may be worth your while to spend the money on a perc test.
Think about topography.
What does the topography of your property look like?
Are you on a hill or in a valley?
Does it have a slope?
These features can affect both the soil and water table, which could give you a higher or lower chance of passing your perc test.
Considering these factors may help you decide whether to have one – one way or the other.
Just keep in mind that these context clues are no guarantee that you will ultimately be able to place a septic system on the lot!
14. There are options for a non-buildable property
Alright, so you failed your perc test, and you didn’t have luck with any of the alternatives.
We have some solutions for all of you who won’t be able to install a septic system on the property.
- Storage units
- Pole barns
- Horse stables
- Grazing fields
- Crops & Farming
Don’t lose hope that your land can be put to good use even if your perc test didn’t go the way you’d planned.
A perc test is a simple 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.
Landowners often stress when they receive a failed perc test.
If this happens to you, take a step back.
You can either go through the steps in #5 and try to get a different result, OR you can select one of the alternative uses for your land in #14.
Depending on how much you paid for your land initially, it may not make sense to spend a bunch of money to try to make it “buildable” anyway.
Don’t lose hope!
Additional ResourcesIf you are looking to buy affordable land, you can check out our Listings page. And before you buy land, make sure you check out Gokce Land Due Diligence Program. Don't forget to check out my latest Gokce Knowledge Class: 31 Lessons I Learned Selling My First 500 Properties Online.
If you are looking to sell land, visit our page on how to Sell Your Land.
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Disclaimer: we are not lawyers, accountants or financial advisors and the information in this article is for informational purposes only. This article is based on our own research and experience and we do our best to keep it accurate and up-to-date, but it may contain errors. Please be sure to consult a legal or financial professional before making any investment decisions.