Table of Contents
By LandyDandy
If the land has no sewer line, a home or cabin will usually need a septic system. Whether you can put one in depends on the soil. A perc test, or soil evaluation, is how you find out. Do it before you buy, not after.
General information, not legal, tax or financial advice. Rules differ by state and county and change over time. LandyDandy is a land marketplace, not a law firm, lender or title company. Each seller on LandyDandy sets their own terms. Before you sign or pay anything, check with the county and a licensed real estate attorney or title company in the state where the land is.
The short answer
- Rural land often has no sewer line. A septic system treats wastewater in the soil on your land [S11].
- In most states, the local health department issues septic permits [S10].
- A perc test or soil evaluation shows whether the soil can take a septic system.
- One land consultancy puts the cost at $400–$1,500 [S9].
- If the land fails, you may need a different system, or you may not be able to build at all. Find out before you pay.
How a septic system works
A typical septic system has a septic tank and a drainfield. The drainfield is a shallow, covered excavation made in unsaturated soil. Wastewater percolates into the soil, and the soil removes harmful bacteria, viruses and nutrients [S11].
That last step is the key. If water moves through the soil too fast or too slowly, or if groundwater or rock is too close to the surface, the soil may not do its job. The county may not approve a standard system there.
What a perc test (soil evaluation) is
"Perc" is short for percolation. A classic perc test usually means digging holes, filling them with water, and timing how fast the water drops.
Some states and counties use a broader soil evaluation instead. A soil professional digs test pits and looks at the soil layers and the depth to water or rock. The name and method depend on your state and county.
The result can tell you:
- Whether a septic system can be permitted on the lot.
- What kind of system it would need.
- Where on the lot it can go, which can limit where you build.
Who does it and what it costs
Depending on the county, the test may be done by:
- The county or local health department.
- A licensed soil scientist, engineer or septic designer.
- A licensed installer, with the health department reviewing.
Start by calling the county health or environmental health department. Ask who does soil evaluations there and what the steps are.
One land consultancy puts a perc test or soil evaluation at $400–$1,500 [S9]. You may also need to pay for digging test pits and for a permit application. Costs vary, so get a written quote.
Ask the seller first. Some sellers already have a perc test or an approved septic permit. Ask for a copy, the date, and the county's approval. Old results may have expired or may not meet current rules. Confirm with the county.
What if the land fails?
A failed test does not always mean "no." It can mean:
- A different location on the lot may pass.
- An engineered or alternative system may be allowed. These can cost more to build and maintain. Ask the county which types it allows.
- The land may not be buildable for a home with plumbing. It may still work for camping, hunting or recreation, if the county allows that use. See camping on vacant land.
Some cheap lots are cheap because they do not perc. That is fine if you never plan to build. It is a problem if you do.
Questions to ask before you buy
- Is there sewer service nearby, and can this lot connect?
- Has the land ever had a perc test or soil evaluation? Can I see it?
- Is there an existing septic permit? Is it still valid?
- What does the county require before it issues a building permit?
- What is the minimum lot size for a septic system and well together in this county?
- How far must a septic system be from a well, a creek or a property line?
- If I need a well, where can it go? (See how much value a well adds to vacant land.)
Make the purchase depend on the test
If you plan to build, put a perc or septic contingency in the purchase agreement. That lets you cancel and get your deposit back if the land does not pass in a set number of days. Ask the seller for permission to dig test pits before closing. A local attorney or title company can help you word it.
With owner financing, this matters even more. You do not want to make years of payments on a lot you cannot use the way you planned.
Frequently asked questions
What is a perc test?
A perc test measures how fast water soaks into the soil. It helps show whether the land can support a septic system. Some states and counties use a wider soil evaluation that also looks at soil layers and depth to groundwater or rock.
How much does a perc test cost?
One land consultancy puts a perc test or soil evaluation at $400–$1,500. You may also pay for digging and a permit application. Prices vary by county, so get a written quote.
Can you build on land that fails a perc test?
Sometimes. Another spot on the lot may pass, or the county may allow an engineered system, which can cost more. In some cases a home with plumbing is not allowed. Ask the local health department.
Who approves septic systems?
In most states, local health departments issue construction and operating permits for septic systems under state laws. The EPA does not regulate single-family home septic systems.
Should I buy land before a perc test?
If you plan to build, it is safer to test first or make the sale depend on the test result. If you only plan to camp or hunt, a test may not matter, but check the county's rules for that use.
Next steps on LandyDandy
Ask the seller about septic and perc results using the message button on any listing. Browse land for sale across the US or owner-financed land, and read how to buy land before you pay. For septic rules on a specific lot, talk to the county health department and a local real estate attorney or title company.
Sources
- [S9] Landisle Consulting — Land due diligence (2026) — https://landisleconsulting.com/land-due-diligence — perc test / soil evaluation cost range.
- [S10] EPA — Frequent questions on septic systems — https://www.epa.gov/septic/frequent-questions-septic-systems — local health departments issue permits in most states; EPA does not regulate single-family home septic systems.
- [S11] EPA — How your septic system works — https://www.epa.gov/septic/how-your-septic-system-works — tank and drainfield; drainfield in unsaturated soil; soil treats the wastewater.