County permits
Septic Permits in Harris, Montgomery and Liberty County, TX
Three counties around Lake Houston, three permit offices. Here is what two of them say on their own pages, and what this site has not read.
In short
- Harris: unincorporated property outside public sewer
- Montgomery: 0.75 acre, or 1.5 acres with a private well
- Liberty (Dayton): not read here, ask the county
- Summaries read November 2, 2026; the county controls
Side by Side
| Harris County | Montgomery County | Liberty County | |
|---|---|---|---|
| Office | County Permit Office, Office of the County Engineer | Environmental Health Services, Permits/Floodplain Administration, 501 N. Thompson, Suite 100, Conroe | Not read for this site |
| Covers | Property in Harris County not within any city's limits | Montgomery County (New Caney and Porter are there) | Not read for this site |
| When a permit is needed | New system on property not within reach of a public sewer line; installing or upgrading a system | New systems and add-on modifications; the guide does not say whether repairs need one | Not read for this site |
| Who designs | Registered professional engineer or registered sanitarian: drawings and site evaluation | Registered site evaluator for soil analysis; registered sanitarian or professional engineer for a sealed design (three sets) | Not read for this site |
| Who installs | TCEQ-registered installer, or the homeowner | The guide does not address installer licensing | Not read for this site |
| Lot size | Not stated on the page read | At least 0.75 acre without a private well; at least 1.5 acres with one; lots recorded or on tax rolls before December 1, 1986 may get special consideration | Not read for this site |
| Fees | No county fee listed; engineer or sanitarian generally $300 to $700, installation generally $5,000 to $10,000 | New residential $295; new commercial $345; add-on modification $145; reinspection $135 (each includes a $10 TCEQ assessment where noted) | Not read for this site |
| Timing | Plan review takes three to five days; no development permit until the septic permit is issued | Request an inspection by 3:00 p.m. two business days before; Notice of Approval comes before backfilling | Not read for this site |
| Questions | Permanent-power release after all inspections pass: 713-274-3900 | Main (936) 539-7836; questions (936) 539-7839 | Ask the county's environmental health office |
Source: Harris County Office of the County Engineer, Wastewater FAQ (oce.harriscountytx.gov), read November 2, 2026; Montgomery County Environmental Health Services, “How to Obtain a Septic” permit guide (county document center), read November 2, 2026
Dayton and Liberty County
Dayton sits in Liberty County, which has its own environmental health office and its own process. This site has not read Liberty County's pages, and the one source found that describes them was a third-party directory that cited no government document. That is not good enough to print a rule, so none is printed.
If you are in Dayton, call the county before you plan a repair or a new system, and ask the pro what he has dealt with in that county. Do not assume Harris or Montgomery rules apply.
What the Pro Handles, and What Stays With You
The registered professional designs, the installer builds, and the pro you talk to through this site files or coordinates the paperwork that goes with the job. The owner signs as the owner, supplies the legal description, and in Montgomery County supplies a notarized power of attorney if someone else applies on the owner's behalf. Nothing on this site files anything with a county.
Common Questions
Which county am I in?
Check your property record on the appraisal district's website for the county named there; do not rely on the mailing address or the school district. In rough terms Huffman, Crosby, Humble, Atascocita and Kingwood sit in Harris County, New Caney and Porter in Montgomery County and Dayton in Liberty County, but lots near county lines and inside city limits are exactly where that rule of thumb fails.
What if my property is inside a city?
Harris County's page says its permit office covers property in Harris County that is not within any city's limits. Inside a city, the city's own rules apply, and this site has not read any city's.
Does the permit office have to approve before I dig?
Both counties read here put the permit first. Harris County will not issue a development permit until the septic permit is issued; Montgomery County requires a Notice of Approval after installation and before backfilling. Ask the county before moving any dirt.
Not sure which county you are in?
Call. The pro knows which office handles which road.