Who digs the test pit?

The property owner or contractor usually arranges an excavator to open the pit, and a licensed soil scientist or registered soil evaluator reads the profile. Some firms coordinate both. Confirm local requirements before scheduling.

How many test pits are needed?

It depends on the size of the proposed drainfield and the variability of the site. Some evaluations need only one or two pits; larger or more complex sites need several so the soil is characterized across the whole area.

Is a test pit the same as a soil boring?

They serve the same purpose, reading the soil profile, but a boring is a narrow hole made with an auger or probe while a test pit is an open excavation. Some sites use one method, some use the other, depending on soil and access.

What if the soil profile looks bad?

A poor profile does not always mean no septic system. Restrictive layers, high water tables, or heavy clay may rule out a conventional drainfield but still allow an alternative design such as a mound, pressure-dosed, or drip system. A septic designer can review the findings and recommend options.

All glossary entries

What is a test pit (soil hole)?

A test pit, also called a soil hole or soil boring, is an excavation dug at a proposed septic or building site so a soil scientist can examine the soil profile in place. It is the most direct way to see what is underground before a system is designed or approved.

What looks fine on the surface often tells a very different story a few feet down. A test pit lets an evaluator read the layers of soil directly, rather than guessing from the lawn.

Why a test pit is dug

A county or health department cannot approve a septic system based on what the ground looks like from above. They need to know what the soil does with water below the surface. A test pit exposes that.

By opening the ground, a soil scientist can read the soil profile: the sequence of layers, their texture and structure, the colors that signal how water moves, and the depth to any limiting layer such as rock, clay, or the water table.

What the soil profile reveals

Topsoil and subsoil layers show texture (sand, silt, or clay) and structure, which together control how fast water moves through the soil.

Color is one of the most important clues. Bright, uniform colors usually mean water drains freely. Gray, blotchy, or mottled colors signal that water sits in the soil for part of the year, which limits where a drainfield can go.

The evaluator also records the depth to a restrictive layer and any sign of a seasonal high water table. These depths often decide whether a conventional system fits, or whether an alternative design is needed.

How deep test pits go

Depths vary by jurisdiction and by what the evaluator finds, but pits for septic evaluation are commonly dug several feet deep so the profile can be read well below where the drainfield would sit.

Open excavations have real safety rules. In the United States, OSHA limits how deep a person may enter an unprotected excavation, so many soil scientists read the profile from the surface or from a shored pit and follow trench-safety requirements.

Test pit vs. perc test

A perc test measures how fast water drains from a hole. A test pit lets the evaluator see the whole soil profile and interpret why it drains the way it does.

Many jurisdictions now rely on the soil profile evaluation from a test pit as the primary determination, with a perc test as a supplement or, in some states, no longer required at all. Always confirm which applies with the local health authority.

How ServGround fits in

ServGround manages the workflow around test pits and soil evaluations: client intake with the parcel and property details, scheduling the site visit, generating the proposal and invoice, collecting payment, and delivering the soil report through a client portal that stays locked until the invoice is paid.

See soil testing software

This article is for educational purposes only. Requirements vary by jurisdiction. Consult your state's licensing board or local authority for specific requirements that apply to your project.

Frequently asked questions

Who digs the test pit?: The property owner or contractor usually arranges an excavator to open the pit, and a licensed soil scientist or registered soil evaluator reads the profile. Some firms coordinate both. Confirm local requirements before scheduling.
How many test pits are needed?: It depends on the size of the proposed drainfield and the variability of the site. Some evaluations need only one or two pits; larger or more complex sites need several so the soil is characterized across the whole area.
Is a test pit the same as a soil boring?: They serve the same purpose, reading the soil profile, but a boring is a narrow hole made with an auger or probe while a test pit is an open excavation. Some sites use one method, some use the other, depending on soil and access.
What if the soil profile looks bad?: A poor profile does not always mean no septic system. Restrictive layers, high water tables, or heavy clay may rule out a conventional drainfield but still allow an alternative design such as a mound, pressure-dosed, or drip system. A septic designer can review the findings and recommend options.