New Aerobic Septic System Installation in Montgomery County

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Why so much new construction here means an aerobic system

Most of Montgomery County outside Conroe's core sits on private septic, not a municipal sewer line. On a lot big enough for a wide conventional drainfield, a gravity system can still work. But a huge share of the new building going on right now, especially the one- to two-acre subdivisions along FM 1488 and FM 2978 near Magnolia and Pinehurst, and the infill lots going up around Lake Conroe in Willis and Conroe's Longmire area, simply doesn't have the room or the soil for it. An aerobic treatment unit uses a much smaller drainfield footprint and treats the effluent before it's sprayed, which is exactly why it's become the default system for new builds on tighter lots across the county.

How the installation actually goes, step by step

1. Site evaluation. A licensed evaluator checks your soil type, water table depth, slope and lot size to confirm what kind of system your lot needs and how big the spray field has to be.
2. Design and permit application. We put together the system design, tank size and spray-field layout and file it with Montgomery County Environmental Health as an OSSF permit application, along with the site evaluation.
3. Permit approval. The county reviews the design before anything gets dug. This step gets skipped by installers in a hurry more often than you'd think, and skipping it puts the whole system's legal status at risk.
4. Installation. Once approved, we set the tank, run the spray-field lines, wire the control panel and pressure-test the system.
5. Pre-cover inspection. A county inspector reviews the open trench and tank before backfill to confirm it matches what was approved. We don't cover anything until that sign-off happens.
6. Backfill and startup. The system gets covered, and we start up the aerator, pump and panel and confirm everything's running the way it's supposed to.
7. Maintenance contract. Every aerobic system has to be under a licensed maintenance contract from the moment it goes live. We set your first contract term at install, so there's no gap.

What it costs

Installing a new aerobic system on a lot that doesn't already have one typically runs $9,000 to $15,000, depending on tank size, spray-field length and how far the equipment has to travel down your driveway. Replacing a failed system, where an old tank has to be pumped out and pulled first, generally lands higher, commonly $12,000 to $20,000 once demolition and disposal are added in. See our pricing page for the full replacement breakdown. Either way, we walk the lot with you and give you a number before you sign anything, not a placeholder that changes once we've started digging.

What makes an install harder than the standard job

A handful of site conditions come up again and again in this county and change what a job takes. A high water table, common on lower lots near Lake Conroe, can force a raised or mound-style spray field instead of a flat one. Heavy clay soil, which runs through a lot of the ground around Magnolia and Pinehurst, drains slowly and can require a larger spray-field footprint to meet the county's design requirements. Tight lot lines near a well, a neighbor's property or the lake itself sometimes mean the layout has to be reworked from a standard design. And on a lot that already had an old system fail, we sometimes find abandoned tanks, lines or a spray field from a prior install that has to be located and dealt with before the new one goes in.

How long it takes

Site evaluation through permit approval generally takes 2 to 4 weeks, most of that sitting with the county's review queue rather than our schedule. Once the permit's in hand, the physical installation itself is usually 1 to 3 days. Add a few more days for the county's pre-cover inspection to get scheduled, and you're looking at roughly a month from first call to a working system, faster if the permit review moves quickly, longer during the county's busier building seasons.

One thing we won't do

We don't break ground before the permit's approved, even if a previous owner or another contractor tells you it's fine to get started while the paperwork catches up. It isn't fine, and it's the fastest way to end up with a system the county won't recognize. If you haven't had a site evaluation done yet, that's the first call, not the last.

Building along FM 1488, on an infill lot near Seven Coves or Longmire, or replacing a system that's finally given out? Call (936) 220-4717 and we'll get a site evaluation scheduled. Already have a system and just need it maintained or repaired? See aerobic septic repair or our FAQ page.