Why So Many Conroe Homes Run on Wells and Septic — A Montgomery County Owner’s Guide

Drive ten minutes in any direction out of downtown Conroe — up I-45 toward Willis, out TX-105 toward Montgomery and the lake, east toward Cut and Shoot and Grangerland — and you cross an invisible line that matters more than any school zone: the edge of city water and sewer. Beyond it, every house is its own utility company. This guide explains how that happened, what’s actually under the ground here, who regulates what, and the short list of things every well-and-septic household in Montgomery County should know.

Why doesn’t my Conroe-area home have city water and sewer?

Because growth outran pipes, and Texas lets it. Conroe’s population has more than doubled since 2010 — from about 56,000 to roughly 125,000 — and it has repeatedly appeared on national fastest-growing-cities lists, with housing units up about 37% just from 2019 to 2024. Much of that growth, plus decades of earlier settlement, sits in unincorporated Montgomery County, where there is no city utility to extend. Some subdivisions formed municipal utility districts (MUDs) and got central water and sewer; acreage communities, older subdivisions, and rural tracts didn’t. For them the development pattern is fixed: a private water well permitted through the groundwater district and a septic system permitted through the county — which is why county guidance requires at least 1.5 acres for a lot carrying both.

This isn’t a fringe arrangement. It’s the default for a large share of the county, and it works fine — provided owners know they’re the operator.

What aquifer is under Conroe?

The Gulf Coast Aquifer System: stacked, alternating layers of sand and clay laid down by ancient rivers, holding fresh water at multiple depths. Under Montgomery County, top to bottom, the named layers are the Chicot, Evangeline, and Jasper aquifers, with the Catahoula formation beneath. Water quality in the shallower portions is generally good. Public water systems here pump overwhelmingly from the Evangeline (roughly half of permitted pumping in recent decades) and the Jasper (roughly 40–45%); private residential wells around Conroe are commonly completed in the 150–400 foot range, depending on location.

Two things make this aquifer story unusually political for a homeowner topic:

• The water table has been dropping. Heavy pumping for a booming population lowered water levels enough that regulators forced change (next section). Deeper completions and conservative pump settings are how well owners hedge.
• The ground itself moves. Pumping water out of compressible clay layers causes land subsidence — the slow sinking of the land surface. A 2000–2020 study found roughly half of Montgomery County subsiding at more than 5 millimeters per year, driven mostly by compaction in the Evangeline and Jasper aquifers. Subsidence here is measured in millimeters, not the feet that famously sank parts of Harris County — but it’s the reason groundwater management got teeth.

Who regulates wells and septic in Montgomery County?

Three names worth knowing:

1. Lone Star Groundwater Conservation District (LSGCD) — created in 2001 to manage Montgomery County’s groundwater. Every well in the county must be registered with LSGCD. A typical single-family well is exempt (incapable of producing more than 25,000 gallons/day, serving a home or livestock): it must be registered, and spacing rules apply, but it needs no operating permit and no meter. Large users — utilities, not homeowners — hold permits, meter their pumping, and report annually.
2. San Jacinto River Authority (SJRA) — operator of Lake Conroe, the 21,000-acre reservoir completed in 1973 on the West Fork of the San Jacinto River as a water supply for Houston and the region. Under the countywide Groundwater Reduction Plan, large-volume users had to cut groundwater use to no more than 70% of their 2009 permitted amounts by 2016, and since 2015–2016 SJRA has treated Lake Conroe surface water (a 30-million-gallon-per-day plant and a 55-mile pipeline) for cities and utilities — including Conroe and The Woodlands. That conversion exists to take pressure off the aquifers your private well depends on. Homeowner takeaway: the lake is the utilities’ alternative supply; your exempt well stays on groundwater.
3. Montgomery County Environmental Health Services — the permitting authority for septic systems (on-site sewage facilities, or OSSFs) under TCEQ’s statewide rules. Office: 501 N. Thompson, Suite 100, Conroe; (936) 539-7836, septic line (936) 539-7839.

What are the septic rules in Montgomery County?

The short version of the county’s published process:

• New systems require a site evaluation with soil analysis by a Registered Site Evaluator, a design sealed by a Registered Sanitarian or Professional Engineer, floor plans, a floodplain determination, and a $295 permit ($285 county + $10 TCEQ). The county requires three sets of the design.
• No septic permits in the regulatory floodway. Floodplain status is checked at the permit office for every application.
• Lot sizes: at least 0.75 acre for septic on public water; at least 1.5 acres for septic plus a private well, with special consideration for lots recorded before December 1, 1986 when separation distances still work.
• Separation distances protect drinking water: a soil absorption field or spray area must be at least 100 feet from a private well (150 from public wells); tanks must be 50 feet from wells; fields keep 50–75 feet from creeks, ponds, and the lake.
• Inspection before burial: a county Notice of Approval must be obtained after installation and before backfilling.
• Repairs: tank replacement and drain field work need permits; true emergency repairs that don’t require removing the tank are exempt but must be reported to the county within 72 hours.

Why so many systems here are aerobic (with sprinklers in the yard): much of the county’s soil profile is sandy or loamy topsoil over slowly draining clayey subsoil. Where the required soil analysis finds restrictive clay, a conventional buried drain field can’t be approved, and the design moves to an aerobic treatment unit with surface or drip distribution. Aerobic systems treat to a higher standard but carry an ongoing obligation: TCEQ rules keep them under recurring professional inspection (typically every four months), which in practice means a maintenance contract most owners renew for $300–$600 a year (2026 Texas figures).

What every well-and-septic owner in Conroe should actually do

A realistic owner’s checklist — the whole job in six lines:

1. Test the well water annually for coliform bacteria, nitrate, and total dissolved solids (Texas Well Owner Network/TCEQ guidance; basic tests from ~$20–$30). Details →
2. Pump the septic tank on schedule — roughly every 2.5–3 years for a four-person household with a 1,000-gallon tank, per TCEQ. Details →
3. Keep the aerobic maintenance contract current if you have one — it’s a compliance requirement, not an upsell. Details →
4. Know your paperwork: the state well report and LSGCD registration for the well; the county permit, design, and Notice of Approval for the septic. Both systems have files; pull them once and keep copies.
5. Respect the 100 feet between the well and anyone’s drain field — yours or a neighbor’s — before adding structures, pools, or a new system component.
6. At purchase or sale, inspect both systems inside the option period — Texas requires neither inspection by law. Details →

Frequently asked questions

How many homes in Montgomery County are on septic systems?

No single public count exists, and we won’t invent one. What’s documented: septic permitting runs continuously through Montgomery County Environmental Health Services, the county publishes lot-size and design rules specifically because on-site systems are standard outside utility districts, and unincorporated growth has been rapid for decades. “Tens of thousands of households” is the honest order of magnitude.

Is Conroe’s groundwater running out?

Not in a turn-on-the-tap-and-nothing-happens sense — but levels declined enough that regulators acted. Large users were required to cut groundwater pumping to 70% of 2009 permitted amounts by 2016, with Lake Conroe surface water making up the difference. Private exempt wells weren’t the target; drilling adequately deep is still the prudent hedge.

Why is there a sprinkler system in my yard that isn’t for the lawn?

Those are spray heads for an aerobic septic system — they distribute disinfected, treated effluent because the soil under much of Montgomery County drains too slowly for a conventional buried field. The system behind them requires recurring professional inspection under TCEQ rules. Don’t cap, move, or irrigate-over them without talking to a licensed provider.

Does Lake Conroe supply my drinking water?

Only if you’re on a participating utility. SJRA treats Lake Conroe water and wholesales it to cities and utilities under the Groundwater Reduction Plan; private wells take nothing from the lake. The reservoir itself — completed in 1973, about 21,000 acres, normal pool 201 feet above sea level — was built as a water supply first, recreation second.

What’s the minimum lot size for a well and septic in Montgomery County?

County guidance: 0.75 acre for a septic system alone (public water), 1.5 acres where the lot carries both a septic system and a private well. Lots recorded or on the tax rolls before December 1, 1986 can receive special consideration if minimum separation distances — like 100 feet from drain field to well — can still be met.

Who do I call about a neighbor’s sewage surfacing or a suspect abandoned well?

Montgomery County Environmental Health Services ((936) 539-7839) handles OSSF complaints — surfacing sewage is a violation, not a neighborly quirk. For abandoned or deteriorated wells, the Lone Star Groundwater Conservation District is the local contact; Texas has plugging standards because open wells are direct contamination pathways into the aquifer everyone here drinks from.

Questions about your own well or septic? request a quote online — free, no obligation.

JM Marketing Co is a referral service. Facts on this page come from public sources — Montgomery County Environmental Health Services, TCEQ, the Lone Star Groundwater Conservation District, the San Jacinto River Authority, the Texas Water Development Board, USGS, and the U.S. Census — and we qualify what we can’t verify. Corrections welcome via the contact page.