Verified against county records · sources last read August 31, 2026 · rules change — confirm with the agent before applying
A new residential septic permit in Montgomery County costs $350 plus a $10 state fee. Two rules decide whether you can get one at all: a sewer main within 300 feet of your building site disqualifies a septic system outright, and property within 2,075 feet of Lake Conroe is permitted by the San Jacinto River Authority rather than by the county.
If an organized disposal system runs within 300 feet of any part of your proposed septic system, you cannot install one. Section 10(l) of the county Order:
“No person may cause or allow the installation of an OSSF when any part of the OSSF is located within three hundred feet in horizontal distance (measured on the closest practicable access route) of an existing Organized Disposal System, with the exception of written denial of service from the owner or governing body of the Organized Disposal System.”
An organized disposal system means a sewer utility. The measurement is along the practicable access route, not straight-line, which usually works in the applicant’s favor on awkward lots.
The escape hatch is the written denial. This is why the county’s new-septic checklist demands a “Letter on Utility District Letterhead (date within the past year)” that “must explicitly state water and sewer will be provided to the specific address,” and warns that “letters stating only ‘capacity’ will be rejected.”
That ring moves, and it moves fast here. Montgomery County added 30,011 residents between July 2024 and July 2025, which the Census Bureau ranks fourth among all United States counties by numeric growth for that year. Utility districts extend service into that growth constantly. A neighbor’s lot that took a septic permit three years ago tells you nothing about yours, so get the utility letter before you pay a designer.
Neither of the two national septic sites covering Montgomery County mentions this rule.
Montgomery County has two septic permitting authorities, and the boundary is a distance from Lake Conroe. TCEQ’s authorized-agent database lists both as current:
| Authority | Area served, per TCEQ |
|---|---|
| Montgomery County Authorized Agent (AR 620145) | “entire County except unincorporated area w/in 2075ft of Lake Conroe (San Jacinto River Auth jurisdiction)” |
| San Jacinto River Authority (AR 620146) | “all area w/in 2,075 ft of Lake Conroe, except within any City limits” |
SJRA’s own rules put it plainly: OSSFs within 2,075 feet of the reservoir “are subject to regulation and permitting by SJRA” under its Order Adopting Rules for On-Site Sewage Facilities Within 2,075 Feet of Lake Conroe, Texas, passed December 10, 2015 and in force since June 1, 2016.
SJRA’s rules are stricter than the county’s on the thing that matters most. Its Section 7(a)(1) requires “All lots utilizing an OSSF and being served by a public water system must be at least one acre, and all lots not served by a public water system must be at least one and one half acres in size.” The county’s equivalent minimum is three-quarters of an acre on public water. Same lake, different side of an invisible line, and a quarter-acre difference in what you can build on.
| Montgomery County | SJRA (within 2,075 ft of Lake Conroe) | |
|---|---|---|
| Office | 501 N Thompson St, Suite 101, Conroe TX 77301 | 1561 Damsite Rd, Conroe TX 77304 |
| Phone | (936) 539-7839 | (936) 588-1111 |
| Contact of record | Keith Miles, OSSF Supervisor | Shane Simpson |
| New permit fee | $350 + $10 state fee | $300 |
| Re-inspection | $150 | $260 |
| Minimum lot, public water | 3/4 acre | 1 acre |
| Applications | Paper, in person | Online customer portal |
SJRA publishes an OSSF data viewer that will tell you which side of the line a parcel sits on. Its permitting page also states the process requires “Up to Thirty (30) Days to Process.”
Two things SJRA does not publish: the contract filing fees, late fees and administrative fees its own Order Section 10(a) authorises. Its posted rate schedule was adopted in September 2010, five years before the septic order it now serves, and lists only the $300 construction fee and the $260 re-inspection fee. Budget for those two and ask about the rest.
One boundary question we cannot answer for you. TCEQ’s record describes the county’s territory in a way that reads as including incorporated cities. The county’s Order Section 6 says its rules apply “except for the area regulated under an existing rule or ordinance and the areas within incorporated cities,” and extend into cities only where an intergovernmental contract exists. No city in Montgomery County holds TCEQ delegation of its own. If your property is inside Willis, Magnolia, Splendora, Panorama Village or another municipality, the two records disagree about who handles you, and we are not going to pick the more convenient reading. Call the Permit Office at (936) 539-7836 and ask before you file. Our Texas septic permit authority directory records the agent of record for every county.
Three-quarters of an acre with public water, an acre and a half without. Order Section 10(e):
“Subdivisions of single family dwellings platted or created on or after December 16, 1986, served by public water supply, and using individual OSSFs for sewage disposal, shall have lots of at least three-fourths (3/4) acre.”
Without public water, or with public water plus a private well on the same lot, the minimum is one and one-half acres. Commercial facilities need one acre with public water and one and a half without, and those minimums do not apply to lots in subdivisions platted before December 16, 1986.
That grandfathering date is worth care. The county’s own homeowner handout, revised March 2023, prints December 1, 1986 instead. Fifteen days apart, in the document a homeowner actually reads. The adopted Order controls, and the Order says December 16. If your lot was platted in that fortnight, get the county to confirm in writing which date it is applying to you.
Both authorities have closed the state’s ten-acre exemption. Montgomery County Order Section 10(g): “A permit shall be required for all OSSFs regardless of the size of the lot or acreage onto which the OSSF is installed.”
SJRA Section 7(a)(3) does the same inside its ring: “All OSSFs, regardless of the size of the property served, must meet all requirements of the Rules and the Authority and must be permitted by the Authority.”
The state rule they both overrode sets four conditions, all of which must hold: ten acres or more, one dwelling only, every component a hundred feet clear of the property line, and the effluent disposed of on the tract. Meet all four and the state asks for nothing. Montgomery County and SJRA both ask anyway, as Texas law lets them. Our Texas ten-acre rule guide tracks which counties still honor it.
The fee schedule effective June 2, 2025 sets a new residential septic permit at $350, and doubles the count of tiers by splitting everything on whether the property is in the floodplain.
| Fee | Amount |
|---|---|
| Residential, new | $350 + $10 |
| Residential, new, floodplain | $480 + $10 |
| Residential, add-on | $135 + $10 |
| Residential, add-on, floodplain | $270 + $10 |
| Commercial, new | $400 + $10 |
| Commercial, new, floodplain | $550 + $10 |
| Commercial, add-on | $200 + $10 |
| Commercial, add-on, floodplain | $335 + $10 |
| Reinspection | $150 |
| Non-compliance administrative fee, per incident | $200 |
| Subdivision review | $340 |
| Redraw | $0 |
| Septic disclaimer | $0 |
The floodplain tier is a $130 difference on a new residential permit, and floodplain status is determined by the Permit Office rather than by you. The $10 on each line is the state’s, collected for TCEQ under Order Section 12.
Commissioners Court approved this schedule on May 13, 2025 with an effective date of June 2, 2025. The document itself carries no date on its face, which is worth knowing if someone hands you a printout.
The county warns that its own forms are out of date. Its permitting page states: “THE PERMIT OFFICE IS IN THE PROCESS OF UPDATING APPLICATIONS. THE CORRECT FEES ARE LISTED ON THE UPDATED FEE SCHEDULE.” Pay from the schedule, not from the application packet.
There is no license-to-operate fee, no transfer fee, no maintenance contract filing fee and no variance fee on the schedule, and no expedited review exists at any price. Compare across the state in our Texas septic permit fee index.
Montgomery County has not moved this process online. The handout’s header is explicit: “Montgomery County requires three (3) sets of the Design.” Everything is printed 8.5 x 11, single sided, on white paper, and the Permit Office “will not print emailed paperwork or make copies.” Fees are exact check or money order made payable to Montgomery County, one payment per permit, and all of it non-refundable.
Before you apply you need a site evaluation including a soil analysis from a Registered Site Evaluator who is registered in Montgomery County, and a design from a Registered Sanitarian or Registered Professional Engineer. Order Section 10(f) requires that all planning materials be “prepared by a professional engineer or professional sanitarian with appropriate seal, date, and signature.”
Applications go to the Montgomery County Permit Office at 501 North Thompson, Suite 100, Conroe, open 8:00am to 3:00pm. The septic permit is pulled together with a development permit; the county says you cannot obtain one separately from the other.
The county publishes no review-time commitment. The deadline that governs is the state’s, at 30 TAC § 285.3(c): the permitting authority must approve or deny within 30 days of receiving an application. SJRA independently publishes the same 30 days for its own process.
Once issued, the authorization to construct expires one year from its date. There is no extension product, at any fee, despite what one competitor publishes.
At the end, the inspection: a Notice of Approval must be obtained after installation and before the system is backfilled or used, and the request has to reach Environmental Health by 3:00pm two business days before the day you need the inspection. That is tighter than the state’s five-working-day installer notification and it is the step that most often costs a week.
The county also gates the packet on a Precinct 4 culvert verification where applicable, stormwater compliance certification, engineering signoff over 15,000 square feet disturbed, and MC911 address verification.
No septic system may be installed in the regulatory floodway, and only aerobic systems may be installed in the floodplain. Order Section 10(h) requires that risers, chlorinator, clean-outs, inspection ports, control panels and compressors all sit above base flood elevation, that everything else be “completely buried without adding fill,” that sprinkler systems carry backflow prevention, and that pump tanks be strapped with three-eighths to one-half inch ten-thousand-pound steel cable to treated posts. Buoyancy calculations are required on all septic pump tanks.
Distances from water come from the state table at 30 TAC § 285.91(10) rather than from any county rule: 50 feet from streams, ponds, lakes, rivers and creeks to tanks, 75 feet to a soil absorption system, reduced to 50 feet with secondary treatment and disinfection, and 50 feet for surface application.
There is no lake-specific setback in the county Order. We checked the full adopted text; the words lake, Conroe, reservoir and shoreline do not appear in it. What governs near Lake Conroe is SJRA’s jurisdiction, not a county setback.
Ninety-nine percent of new systems authorized in Montgomery County in 2025 were spray or drip. TCEQ’s report of systems installed by time period, covering calendar 2025, records 1,821 authorizations to construct issued by the county:
| System type | Authorizations, 2025 |
|---|---|
| Surface irrigation | 1,469 |
| Drip irrigation | 336 |
| Standard trench or bed | 11 |
| Gravel-less | 2 |
| Leaching chamber | 2 |
| Low pressure dosing | 1 |
Eleven conventional drainfields out of 1,821. SJRA’s separate 29 authorizations inside the lake ring were 15 surface and 14 drip, with no conventional systems at all. Statewide, TCEQ recorded 41,990 authorizations in 2025.
The reason is not the one usually given. Montgomery County is often described as heavy clay; the soil survey does not support that. The dominant map units are Conroe loamy fine sand, Fetzer loamy fine sand, Splendora fine sandy loam and Woodville fine sandy loam — sands and sandy loams at the surface. What disqualifies conventional drainfields is what sits underneath and how wet it stays. By our analysis of the NRCS data for the county, roughly a third of the mapped acreage falls in hydrologic soil group D, the highest-runoff class, and well over a third is somewhere between somewhat poorly and very poorly drained.
The county is sandy on top and tight and wet below. 30 TAC § 285.33(b)(1) requires two feet of suitable soil between the bottom of the excavation and either a restrictive horizon or groundwater, and that is the test most of this ground fails.
If you are pricing the result, see our aerobic septic system cost guide and the new septic system cost guide.
An aerobic system in Montgomery County comes with two documents the owner has to sign personally. The county’s checklist flags both with the same warning: owner’s signature only, power of attorney does not cover.
The Affidavit to the Public is notarized and filed at the Montgomery County Clerk’s office. It binds the owner to an initial two-year policy contract with a certified maintenance provider, to keeping a certified provider “during the entire operational life” of the system, and to testing three times a year for pH and chlorine residual with reports to the Permit Division.
The two-year contract itself requires “a minimum of three (3) inspections, one every four (4) months,” with each report submitted to the permitting authority and the owner “within 14 days after the date the test is performed.” Non-residential systems add one BOD and TSS grab sample per year.
Order Section 10(j) closes the homeowner-maintenance route: there is “no homeowner or property owner maintenance of an on-site sewage disposal system using aerobic treatment, unless the homeowner or property owner is also a Certified Maintenance Provider” — which the Order defines as licensed or registered with TCEQ and with Montgomery County. Inside the SJRA ring the rule is different: SJRA does allow owner self-maintenance on an owner-occupied home where the owner holds the right license or has completed the TCEQ Basic Maintenance Provider course or AgriLife B-6235.
Our aerobic maintenance contract guide covers what these contracts must contain and what happens when one lapses.
Montgomery County:
The county publishes courtesy rosters of registered sanitarians and engineers and of installers, both carrying the disclaimer that it “does not recommend or endorse any of these individuals,” and a note that not everyone on the designer list is a state certified site evaluator. There is no county site evaluation form; the state format is what is expected.
For licensed providers working in the county, see our Montgomery County directory and our septic installation service page.
$350 plus a $10 state fee for a new residential system, or $480 plus $10 in the floodplain, under the schedule effective June 2, 2025. Add-ons are $135 plus $10. Commercial is $400 plus $10. Within 2,075 feet of Lake Conroe, SJRA charges $300 instead.
The San Jacinto River Authority, for anything within 2,075 feet of the reservoir and outside city limits. SJRA is a TCEQ authorized agent in its own right under an order in force since June 1, 2016. Its minimum lot size on public water is one acre against the county’s three-quarters of an acre.
Yes. Order Section 10(g) requires a permit “for all OSSFs regardless of the size of the lot or acreage.” SJRA requires one too, inside its jurisdiction. The state’s ten-acre provision does not apply in either.
Not within 300 feet of one, unless the utility refuses you service in writing. Order Section 10(l) prohibits it, measured along the closest practicable access route. The county requires a utility-district letter dated within the past year that explicitly states water and sewer will be provided to your address; a letter mentioning only capacity is rejected.
The county publishes no turnaround. The governing deadline is the state’s 30 days to approve or deny under 30 TAC § 285.3(c). Once issued, the authorization to construct expires one year from its date, and no extension exists. Book the final inspection by 3:00pm two business days ahead, and before the system is backfilled.
Three-quarters of an acre with public water, one and a half acres without, for subdivisions platted on or after December 16, 1986. A lot with public water that also has a private well needs one and a half acres. Lots in subdivisions platted before that date are treated separately, and the county’s homeowner handout prints a date fifteen days earlier than the Order does.
Every fee on this page was read off the Montgomery County Permitting Fee Schedule itself. Because that document prints no date on its face, we established its effective date separately, from the Commissioners Court motion of May 13, 2025 that adopted it.
The Order we quote is the one TCEQ holds as the county’s current rules for authorized agent 620145; the copy the county posts is byte-identical to it, which is how we know we are reading the operative text. Its pages are scans without a text layer, so every quotation here was optically recognized and then re-verified at high resolution, character by character, before it was used.
For the lake ring, jurisdiction and lot minimums come from SJRA’s Board Order 2015-O-04, fees from its own posted rate schedule, and its standing as an authorized agent from TCEQ’s directory record for AR 620146.
System-type counts come from TCEQ’s annual tally of authorizations to construct for calendar 2025, published April 27, 2026. We quote the county row, the SJRA row and TCEQ’s own grand total as printed. Any proportion drawn from them is ours.
Population figures come from the Census Bureau’s Vintage 2025 county population totals release file. The ranking of Montgomery County fourth among all United States counties by numeric growth between July 1, 2024 and July 1, 2025 is Census’s own, published as Table 6 of press release CB26-56 on March 26, 2026, and is stated here with the peer set that table names. We have not published any rank we derived ourselves.
Soil characterisation is our own analysis of USDA-NRCS SSURGO data for survey area TX339, queried through Soil Data Access on August 31, 2026. The map units and drainage classes are NRCS’s; the shares are ours.
Two records disagree in ways we have not resolved and have not papered over: whether the county permits inside incorporated cities, and whether the grandfathering date is December 1 or December 16, 1986. Both are stated above as open, and we have asked the county.
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