What a Perc Test Is and Why It Affects Your Land's Value

If your parcel is rural and not on a public sewer line, one unglamorous factor can quietly determine a big chunk of its value: whether the soil will support a septic system. That’s what a “perc test” checks. Here’s what it means, why buyers care, and whether you need to worry about it to sell.

What a perc test is

“Perc” is short for percolation. A perc test measures how quickly water drains through the soil on your land. That drainage rate determines whether the ground can support a conventional septic system — which is how waste is handled on properties without access to a public sewer.

A licensed soil evaluator or the county health department digs test holes and measures how fast water percolates. The result tells you:

• Passes (“percs”): the soil drains well enough for a standard septic system. Good news for a buildable homesite.
• Fails or needs an alternative system: the soil drains too slowly (or too fast), so a conventional septic won’t work. The land may need an expensive engineered/alternative system — or may not be buildable for a home at all.

Not engineering or health-code advice. Septic rules, test procedures, and who can perform them vary by state and county. Confirm specifics with your local health department.

Why it matters so much for value

For a parcel being sold as a potential homesite, septic viability is close to make-or-break:

• Land that percs and can clearly support a home commands a premium — a buyer can build.
• Land that won’t perc is worth far less as a homesite, because a buyer either can’t build a conventional home or faces a large extra cost for an alternative system.

It sits right alongside road access as one of the factors that most separates “buildable and valuable” from “limited-use and discounted.” Two otherwise-identical parcels can differ substantially in value based purely on their soils.

When does it not matter much? If the land is being valued for non-residential use — timber, hunting/recreation, agriculture, or as an add-on to an adjacent property — septic viability may be largely irrelevant, and the parcel is priced on other factors.

Do you need a perc test to sell?

Usually no — not on your dime, anyway.

• Selling to a retail buyer who plans to build: they’ll often want a perc test, but frequently the buyer orders it during their due diligence, sometimes as a contingency. You don’t necessarily pay for it.
• Selling to a cash buyer: you don’t need to test anything. When you sell to us, we handle due diligence ourselves — no perc test, no survey, no soil work for you to arrange or pay for. We factor buildability into our offer based on the parcel’s characteristics.

So if you were worried you’d have to arrange and pay for soil testing before you could sell, you generally don’t.

If you already know your soils

If you happen to have an existing perc test, soil report, or a septic permit on file, mention it — it’s a helpful data point that can support value for a buildable parcel. But there’s no need to go out and commission one just to sell.

The bottom line

A perc test checks whether the soil will support a septic system, and for a homesite that answer heavily influences value — passing land is worth notably more than failing land. But you typically don’t need to run one yourself to sell, especially to a cash buyer who does their own due diligence.

Not sure how your parcel’s buildability affects what it’s worth? Get a free cash value range — we account for the land’s characteristics, and there’s nothing for you to test, order, or pay for.