The perc test, by hand

A perc test measures how fast water soaks into the soil where a drain field would go. Done by hand, it goes like this:

1. Dig the test holes. South Dakota's procedure calls for at least three per site.
2. Soak the holes, usually overnight.
3. Refill each hole and have someone stand there with a ruler and a stopwatch, timing each 1-inch drop for two to four hours.
4. Copy the numbers onto the county's form and work out the rate.

That's hours of skilled labor per site, and the readings are only as trustworthy as the person taking them.

With AutoPerc

Here's how AutoPerc is designed to work:

1. The crew sets the AP-1 unit beside the hole and pushes the supplied tube in.
2. They fill the hole by hand, and leave.
3. The unit measures and logs the falling water level on its own. It detects when the official test window starts, times each 1-inch drop, and ends the test when the state's rule is met.
4. It uploads the data and notifies the office.
5. The app lays out the results on the county's report form.

Every reading is stamped with satellite-backed time and position, so each test shows when and where it was run.

How it measures

The tube holds a column of air that's open only at its bottom end, under the water. Deeper water squeezes that air harder, so a pressure sensor inside the box can read the water level from it. As the water soaks into the soil, the pressure falls.

Before each reading, a small pump blows air down the tube to reset the air column and clear mud from the tip, and the sensor re-zeroes against the open air. Nothing but the tube goes in the hole.

Built for South Dakota's procedure

• The test starts when the water falls to 25% of the hole depth. The unit detects this, and the crew can also mark the start by hand in the app, which is logged.
• Each 1-inch drop from there is timed, up to twelve. The hole's rate is elapsed minutes divided by the measured drop, in minutes per inch, and the site rate is the average of the holes.
• The test ends 120 minutes after the start, or 240 minutes if any single inch took longer than 45 minutes.
• Refills show up as a sawtooth in the level trace. The unit detects them, and an interrupted inch is re-timed from the next full inch.

Each state's rules live in a versioned rule pack instead of being built into the unit. Wyoming, Nebraska and Montana are planned.

What it deliberately doesn't do

• No auto-fill. The crew adds water by hand; the unit only measures.
• Nothing in the ground. No probe, sensor or cable below grade, only an air tube.
• No approval claims. Reports are formatted for county submittal. The reviewing authority decides acceptance.

The unit, the app and the dashboard

• The AP-1 is a sealed, weatherproof box with cellular built into every unit, GPS, and Bluetooth for the phone. It has no screen, just status lights and two buttons, and runs on a rechargeable battery charged over USB-C.
• The phone app claims a unit for your company, starts a test, follows it live with the sawtooth trace and the rate so far, and can read a test straight off the unit over Bluetooth. Firmware updates go to the unit only over Bluetooth from the phone, never over cellular.
• The web dashboard shows a map of running tests, the tests list with CSV export, sites and site rates, your units, and your team.

With no signal, the unit stores readings on board and catches up later.

Who it's for

Septic installers, excavators and site evaluators, and civil engineers doing stormwater infiltration testing. AutoPerc is sold to businesses only, never to homeowners.

AutoPerc is still in development. We'll share availability when it's ready. If you'd like to hear when it is, get in touch.