What Is a Perc Test—and Why Can It Make or Break a Land Purchase?

By John S. Wagner, Affiliate Broker/Realtor®
Weichert, Realtors® - Saxon Clark
Serving Kingsport, Johnson City, Bristol, and the surrounding Tri-Cities area

You've found a beautiful piece of East Tennessee land.

It has five acres, mountain views, plenty of privacy, and what looks like the perfect spot for your new home. The price fits your budget, and you're already imagining where the house, garage, garden, and driveway will go.

Then someone asks:

“Has the property been approved for septic?”

That's when buying vacant land can become much more complicated than buying an existing home.

If public sewer isn't available, you will likely need an onsite wastewater system—commonly called a septic system. Before assuming you can simply install one wherever you'd like, you need to know whether the land has suitable soil and an appropriate area for wastewater disposal.

That's where people commonly use the term “perc test.”

And when you're buying land in Kingsport, Johnson City, Bristol, Sullivan County, Washington County, Hawkins County, or elsewhere in Northeast Tennessee, this is something I would want to investigate before buying—not after.

What Is a Perc Test?

“Perc” is short for percolation.

Traditionally, a percolation test measured how quickly water moved through the soil. That information helped determine whether soil could appropriately absorb wastewater from a septic system.

But here's something particularly important for Tennessee buyers:

What people casually call a “perc test” may not literally be the old-fashioned test involving pouring water into holes and timing how quickly it disappears.

Tennessee's current onsite-sewage process relies heavily on soil evaluation and site characteristics when determining whether property is suitable for a subsurface sewage disposal system.

So when someone says:

“Does the land perc?”

what you really want to know is:

“Has this property been properly evaluated and approved for the septic system needed for the home I intend to build?”

That is the more useful question.

Why Does the Soil Matter?

A conventional septic system doesn't simply make household wastewater disappear.

Wastewater leaves the house and enters a septic tank, where solids settle and wastewater is then distributed to a disposal or drain field.

The surrounding soil performs an important part of the treatment process.

If the soil or site conditions aren't suitable, wastewater may not be treated or dispersed properly.

That's why two lots sitting right beside each other can potentially have very different septic possibilities.

One may work well.

The other may have significant limitations.

Beautiful Land Does Not Automatically Mean Buildable Land

This is one of the most important lessons for anyone shopping for acreage.

A property can be:

Beautiful.

Affordable.

Private.

Level in places.

Conveniently located.

…and still present problems for the house you want to build.

Septic suitability is only one component of buildability, but it can be a major one.

That's why I don't like assuming that because a listing says “5 acres”, you automatically have five acres available for whatever you want to do.

The home, septic area, reserve area, driveway, well, utilities, setbacks, easements, streams, slopes, and other site conditions all have to work together.

Tennessee Uses Soil Scientists

For many Tennessee properties, a soil evaluation is a critical part of determining suitability for an onsite sewage system.

Tennessee maintains a roster of approved soil consultants who can perform high-intensity soil maps for septic permitting purposes. The state's process evaluates soil characteristics and site conditions rather than simply asking whether water drains quickly.

A soil scientist may evaluate things such as:

• Soil type

• Soil depth

• Restrictive soil layers

• Seasonal groundwater conditions

• Rock

• Slope

• Landscape position

• Drainage characteristics

• Available usable area

That information helps determine whether the site can support an appropriate wastewater system.

“It Perked Years Ago” Isn't Enough Information

Suppose a seller tells you:

“Oh yes, this land perked 20 years ago.”

That's encouraging.

But I'd want more information.

Where was the approved area?

What size home was it evaluated for?

Is there documentation?

Were regulations different at the time?

Has the property been divided since then?

Has the proposed house location changed?

Has anything been constructed over the approved area?

Old information can be useful, but don't assume an old verbal statement answers today's questions.

Look for the actual documentation.

Septic Approval Can Affect the Number of Bedrooms

Here's something first-time land buyers often don't realize.

Septic-system sizing is commonly connected to the number of bedrooms the system is designed to serve.

Suppose you want to build a four-bedroom home.

Finding paperwork showing that the property was previously approved for a smaller system does not necessarily mean you can automatically build the four-bedroom house you have planned.

This is especially important when shopping for land before choosing a house plan.

Don't think only:

“Can I put a septic system here?”

Think:

“Can this property support the septic system required for the home I actually intend to build?”

Where Will the Septic System Go?

Even when property is suitable for septic, location matters.

You may picture your new home sitting in the most scenic spot on the property.

But the septic system also needs an appropriate location.

That can affect:

• House placement

• Driveway location

• Garage placement

• Outbuildings

• Swimming pools

• Gardens

• Future additions

• Wells

• Property subdivision plans

A septic area is not simply leftover land that you deal with after designing everything else.

It should be considered as part of the overall site plan.

What Is a Reserve Area?

A septic system doesn't last forever.

For that reason, properties may need adequate area available for a replacement or reserve disposal area.

That's important because you don't want to unknowingly build your detached garage, swimming pool, driveway, or other permanent improvement in an area that may someday be needed for septic replacement.

When evaluating a lot, ask where both the initial and any required replacement areas are located.

Don't Drive Heavy Equipment Over the Drain Field

Once you know where a septic disposal area is located, protect it.

Heavy vehicles and construction equipment can compact soil or damage system components.

That means the person planning your:

• Driveway

• House

• Garage

• Construction access

• Material staging area

needs to understand where the approved septic areas are located.

This is particularly important when developing raw land.

What About a Well?

Many rural properties in East Tennessee need both a private well and a septic system.

These systems cannot simply be placed anywhere without regard to one another.

Tennessee's well-construction guidance establishes separation distances from potential contamination sources, including septic tanks and drain fields.

That's why a property that needs both systems requires more planning than:

“We'll put the house here, drill a well over there, and figure out the septic later.”

The pieces need to fit together.

What If the Property Has a Creek or Stream?

Creeks are one of the things that make East Tennessee land beautiful.

But water features can also affect development.

A creek, spring, wet area, drainage channel, pond, or flood-prone portion of a property may reduce the amount of land practically available for construction or septic disposal.

This doesn't automatically make the property undesirable.

It simply means buyers need to evaluate the usable land, not just the total acreage.

Five acres on paper doesn't necessarily equal five acres of buildable land.

Slope Matters in East Tennessee

We have plenty of hills.

A property can look spectacular from the road while having very little conveniently buildable ground.

Slope can affect:

• Septic suitability

• Driveway construction

• Excavation

• Foundation cost

• Drainage

• Erosion control

• Utility installation

• Construction access

Sometimes a lower-priced mountain lot is inexpensive for a reason.

The land price is only one part of the cost of developing it.

What If the Land Doesn't Pass a Conventional Evaluation?

This is where buyers need to avoid jumping to conclusions in either direction.

If a conventional septic system isn't suitable, that does not necessarily mean no wastewater system can ever serve the property.

Alternative or engineered systems may sometimes be possible depending on the site.

But those systems can be more complicated and potentially more expensive.

The correct question becomes:

What type of system, if any, can legally and practically serve this property?

That's a question for the appropriate Tennessee environmental professionals—not something to guess about during a showing.

Alternative Septic Systems Can Change Your Budget

Suppose you budgeted for a relatively straightforward conventional septic installation.

Then you learn that the property requires a more sophisticated system.

Your land may still be perfectly usable.

But your construction budget just changed.

That's why investigating wastewater options before purchasing the property can be so valuable.

A cheap lot isn't necessarily cheap if preparing it for a home costs considerably more than expected.

Can a Property Be Too Small for Septic?

Potentially.

Total acreage by itself doesn't determine septic suitability.

A relatively large parcel might have very little suitable soil.

A smaller parcel might have an excellent approved area.

What matters is the combination of:

soil + usable area + site conditions + proposed home + applicable requirements.

This is another reason not to evaluate land solely by price per acre.

What About Existing Homes With Septic Systems?

A soil evaluation is especially important when buying vacant land, but existing homes create a different set of questions.

If you're buying a house already served by septic, I would want to know:

• Where is the septic tank?

• Where is the drain field?

• How old is the system?

• When was the tank last pumped?

• Are records available?

• How many bedrooms was the system designed to serve?

• Has the system ever had problems?

• Have additions been made to the house?

• Has anything been built over the septic area?

• Is there a known replacement area?

And depending upon the transaction, consider an appropriate septic inspection.

Don't Assume the Seller Knows Where Everything Is

This happens more often than people might expect with older rural properties.

A seller may say:

“The septic tank is somewhere over there.”

That isn't particularly helpful when you're planning an addition or trying to evaluate the system.

Older systems may have limited records, and ownership may have changed several times.

When documentation is available, obtain it.

When location or condition is uncertain, the appropriate septic professional may need to investigate.

Where Do You Start in Tennessee?

Tennessee's Department of Environment and Conservation (TDEC) administers the state's subsurface sewage disposal program and provides information concerning septic-system permitting and records.

You can start with:

Tennessee Septic System Information

For information about septic-system records:

TDEC Septic System Records

Tennessee also operates environmental field offices that can assist with questions about the applicable process for a particular property.

Because procedures, jurisdiction, and required documentation can change, verify the current requirements directly with TDEC or the appropriate local authority before relying on older information.

Can You Look Up an Existing Septic Permit?

For many properties, records may exist showing information about an existing permitted system.

Those records can be extremely helpful.

Depending upon the age and record available, you may be able to learn information concerning:

• Permit history

• Approved system

• Bedroom capacity

• Septic tank

• Disposal area

• Site plan

• Other permitting information

However, don't assume every old rural property will have perfect digital records.

Some older systems predate modern recordkeeping.

The Biggest Mistake: Buying First and Investigating Later

Imagine this scenario.

You find 10 beautiful acres for $80,000.

You buy it with cash.

Six months later you're ready to build your dream home.

Then you begin investigating septic approval and discover that the area where you planned to build isn't suitable.

Now you're trying to redesign the project around land you already own.

That's backwards.

Whenever possible, investigate important feasibility questions before you become committed to the property.

Protect Yourself With the Purchase Contract

When buying land, the terms of your purchase agreement matter tremendously.

Depending upon the transaction, a buyer may want appropriate due-diligence or contingency provisions concerning issues such as:

• Soil evaluation

• Septic approval

• Survey

• Legal access

• Utilities

• Financing

• Zoning

• Restrictions

• Title

• Other feasibility concerns

The exact language and rights involved depend upon the contract.

Don't assume you can simply cancel later because the property doesn't work for your intended use.

Understand your contract before you sign it.

If legal interpretation is needed, consult a Tennessee attorney.

Don't Buy Land Based Solely on the Listing Description

A listing might say:

“Perfect building site!”

That's marketing language.

It isn't a substitute for your own due diligence.

Before buying, investigate whether your intended use actually works.

Ask:

Can I build the type of home I want?

Can I legally access the property?

Is adequate septic approval possible?

Is water available?

Can I get electricity there?

Are there restrictions?

Is part of the property in a flood zone?

What does the survey show?

What will site preparation cost?

Those questions can matter more than how pretty the property looks in photographs.

Questions I Would Ask Before Buying Land That Needs Septic

Here's a checklist worth saving:

1. Has the property previously been evaluated for septic?

2. Is there written documentation?

3. What size system was approved?

4. How many bedrooms can the approved system serve?

5. Where is the approved disposal area?

6. Where is the replacement/reserve area?

7. Has the property changed or been subdivided since the evaluation?

8. Does my intended house location interfere with the septic area?

9. Will the driveway interfere with it?

10. Will a garage or future addition interfere with it?

11. Does the property also require a well?

12. Is there adequate separation between the proposed well and septic system?

13. Are there streams, springs, wet areas, or drainage concerns?

14. How does the property's slope affect development?

15. If a conventional system isn't possible, is an alternative system feasible?

16. What might that system cost?

17. Are septic records available through TDEC?

18. Should I obtain a new soil evaluation before purchasing?

19. Does my purchase agreement give me adequate time to investigate?

20. What other approvals are necessary before I can actually build?

Septic Approval Is NOT the Same as a Building Permit

This distinction is worth emphasizing.

Even if the land can support a septic system, that doesn't automatically mean everything else about your proposed construction has been approved.

You may still need to investigate:

• Building permits

• Zoning

• Setbacks

• Road frontage

• Legal access

• Deed restrictions

• Utility availability

• Floodplain requirements

• Driveway permits

• Survey issues

• Other local or state requirements

Think of septic approval as one major piece of the buildability puzzle—not the entire puzzle.

Why This Matters So Much in East Tennessee

We have tremendous variety in our land.

You can find:

• Level subdivision lots

• Rolling farmland

• Mountain acreage

• Wooded tracts

• Creek-front property

• Old family farms

• Remote rural parcels

• Land overlooking valleys

• Properties close to town but outside sewer-service areas

That's part of what makes buying land here so appealing.

But it also means two properties with the same acreage can be completely different development projects.

One may be nearly ready to build.

The other may require substantial work before construction can begin.

The Bottom Line

When buying land without public sewer, don't ask only:

“Does it perc?”

Ask the better question:

“Can this property be approved for the septic system necessary for the home I actually want to build?”

Then get documentation.

Find out where the usable soil is.

Understand the approved bedroom capacity.

Identify the initial and replacement septic areas.

Consider the well.

Consider the driveway.

Consider the slope.

Consider your future plans.

And don't wait until after closing to begin asking those questions.

When you're buying raw land, knowing what you can do with the property can be just as important as knowing what you paid for it.

Thinking About Buying Land in East Tennessee?

Buying vacant land can be exciting, but it's different from buying an existing house.

Whether you're looking for a building lot, several acres for a new home, a small homestead, mountain property, or a larger rural tract, I'd be glad to help you work through the real-estate side of the process.

I'll help you identify questions to ask and connect with the appropriate professionals when you need expertise involving soil, septic, surveying, wells, construction, lending, title, or legal matters.

Let me help you find what you're looking for in your next home—or the land to build it on.

John S. Wagner

Affiliate Broker/Realtor®
Weichert, Realtors® - Saxon Clark

Cell: 423-276-3392
Office: 423-765-9118
Email: WagsworldRealtor@gmail.com
Website: WagsworldRealtor.com

555 E. Main St Suite 101
Kingsport, TN 37660

Serving Kingsport, Johnson City, Bristol, and the surrounding Tri-Cities and Upper East Tennessee area.

Independently Owned and Operated

This article is intended for general educational and real-estate information and is not engineering, environmental, septic-design, surveying, construction, legal, or permitting advice. Septic suitability and permitting depend on the characteristics of the individual property and current state/local requirements. Buyers should verify information with TDEC and appropriately qualified professionals before purchasing or developing property.

Next in the series: “Buying an Older Home in East Tennessee: What Should You Look For?” — and that one should be especially useful because we can incorporate your 30+ years of electrical experience into the practical things buyers should pay attention to when walking through an older home.