What to Expect During a Septic Install, Week by Week

Published July 1, 2026

Putting a septic system in the ground looks like one big job from the outside, but it is really a series of stages, and each one has to clear before the next begins. If you have never been through it, knowing the order takes the mystery out of the schedule. Here is how a typical install unfolds for a Bangor home.

Week One: The Perc Test and Soil Evaluation

Everything starts with the ground. We dig test holes on your lot, measure how fast water drains through the soil, and confirm the seasonal high water table. Those numbers decide two things: how big the drainfield has to be and whether a conventional gravity system will even pass. On a slow-draining parcel near Stillwater Avenue, the test might point you toward a chamber field or a mound instead. Nothing else can be finalized until this step is done.

Week Two: Permit and Design

With the perc results in hand, we design the system and pull the county health department permit. This is where the tank size gets locked in from your bedroom count, a three bedroom home usually landing on a 1,000 to 1,250 gallon tank. We lay out the drainfield footprint, confirm the setbacks from your well and property lines, and wait for the approval to come back before a single shovel of soil moves.

Week Three: Excavation and Tank Set

Now the work becomes visible. We excavate for the tank and the field, set the watertight tank on a level, compacted bed, and place the distribution box. The inlet and outlet piping gets tied in, and risers bring the access lids up to grade so the system is easy to service later. If you are replacing an old tank rather than starting fresh, our septic tank replacement process fits right into this same stage.

Week Three, Continued: Building the Field

The drainfield goes in next, either gravel trenches with perforated pipe or plastic leaching chambers, sized to the perc rate. We wrap the run in filter fabric, tie it to the D-box, and get everything ready for the inspector. This is the heart of the system, and it is where careful sizing pays off for decades.

Week Four: Inspection, Backfill, and Grade

The county inspects the open system before anything is covered. Once it passes, we backfill, grade the disturbed ground, and seed so the lawn recovers. You get the as built record for your files, which the town and any future buyer will want to see.

Thinking about a system for your property? Learn more about a full new septic system installation or contact us to get on the schedule. Call Theilluum at (207) 739-6388 to book your site visit.