Missouri septic rules

Who regulates septic systems

Cities and counties may adopt the state standard or their own ordinance, which must be at least equal and may be stricter; in most counties the local health department issues permits, in others a sewer district, building or planning and zoning office does, and DHSS enforces the standard where no local body has adopted it. Larger systems, non-single-family lagoons, commercial facilities and subdivisions involve the Missouri Department of Natural Resources (DNR).

• DHSS lists three permitting set-ups by county: DHSS Onsite Program, Local Authority (contract) and Local Authority via Ordinance; pick the county on the permit process page.
• DHSS Onsite Program: 573-751-6095 or toll-free 866-628-9891; OnsiteProgram@health.mo.gov.
• The state construction standards took effect in January 1996.

Sources: RSMo 701.040 (effective Aug 28, 2026), 701.040(1); RSMo 701.035; Missouri DHSS, Onsite Wastewater Treatment; 19 CSR 20-3, Missouri Code of State Regulations, DHSS General Sanitation (9/30/20 compilation), 19 CSR 20-3.060(1)(B)

When you need a permit

A construction permit is required before installing a system or making a major modification or major repair, except on single-family residential lots of three acres or more (and certain lots of ten acres or more) where every part of the system is more than 10 feet from any adjoining property line and no effluent reaches a neighbor's property or pollutes water; some counties do not honor that exemption. Effective August 28, 2026, Senate Bill 914 removed the $90 state permit fee from RSMo 701.046 and DHSS has temporarily suspended its application fees until new fees are set; counties with their own ordinance set their own fees. Property owners may install, modify or repair their own system if they follow the law, and need no permit to clean it.

• Plans and specifications must be approved before a permit to install or make a major repair (19 CSR 20-3.060(1)(C)3).
• Examples of major changes that need a permit: replacing a sewage tank, or replacing or expanding an absorption field (DHSS).
• The 3-acre exclusion does not apply to lots next to lakes run by the Corps of Engineers or a public utility (RSMo 701.031).
• Generally no permit is needed to abandon a sewage tank, but check the county first (DHSS FAQ).

Sources: Missouri DHSS, OWTS Construction Permit Process; Missouri DHSS, Onsite Wastewater Frequently Asked Questions; RSMo 701.055, 701.055(1); RSMo 701.046 (effective Aug 28, 2026), 701.046

Perc tests and soil evaluations

Percolation tests and soil morphology evaluations used to design a system must be done by individuals registered with DHSS. Perc testers qualify through a DHSS course or as an engineer, geologist or soil evaluator; soil morphology evaluators must be soil scientists (15 credit hours of soils, 3 in morphology) or engineers or geologists with 10 soils hours, and pass a written and field exam at 70 percent. DHSS charges registrants a $90 processing fee but publishes no price for the test itself; a 2026 law change says a perc test may be accepted at local discretion only if a soil morphology evaluation cannot reasonably be obtained.

• Registrations last 36 months and require continuing education (19 CSR 20-3.080(7)).
• RSMo 701.040(5), effective Aug 28, 2026, requires a mandatory registration program with continuing education for perc testers before January 1, 2027; that subdivision is void after December 31, 2026.
• Find registered soil evaluators and perc testers on the DHSS Find a Professional map: https://experience.arcgis.com/experience/5c6151e541b74668bbaad632725224fe
• Counties with ordinances may require a soil morphology report for every permit.

Sources: 19 CSR 20-3, Missouri Code of State Regulations, DHSS General Sanitation (9/30/20 compilation), 19 CSR 20-3.080(3); RSMo 701.040 (effective Aug 28, 2026), 701.040(5); Missouri DHSS, Onsite Wastewater Frequently Asked Questions

Licensed installers, pumpers and inspectors

Anyone installing a new system or doing a major modification or repair must be registered with DHSS as a Basic or Advanced installer; only Advanced installers may build advanced systems such as sand filters, mounds, low-pressure pipe and drip. DHSS also registers perc testers and soil evaluators and licenses the inspectors and evaluators who assess existing systems for real estate sales. Registration requires DHSS training with a 70 percent exam score, a $90 fee and renewal every 36 months; verify a pro on the DHSS Find a Professional map.

• A county-issued installer registration counts as a state registration valid statewide (RSMo 701.053).
• Inspecting or evaluating a system for a real estate transaction without a DHSS licence is a class A misdemeanor (19 CSR 20-3.070(16)).
• Many counties with ordinances also require local certification.
• We found no statewide DHSS licence for septic tank pumpers; see unverified.

Sources: Missouri DHSS, Onsite Wastewater Treatment; 19 CSR 20-3, Missouri Code of State Regulations, DHSS General Sanitation (9/30/20 compilation), 19 CSR 20-3.080(4); RSMo 701.053, 701.053(1); RSMo 701.031

Buying or selling a home with a septic system

Missouri law does not require a septic inspection or evaluation before a home is sold, but if a lender or buyer asks for one it must be done by a DHSS-licensed inspector or evaluator, and some counties require one on every sale. An inspection includes a hydraulic load test of the soil treatment system; an evaluation reports tank function and visible signs of failure; both include a private well water sample. State law does not require the seller to fix what the report finds.

FHA does not require a routine septic inspection. The appraiser must visually observe the system and require an inspection only when there are readily observable signs of failure, and the lender must confirm connection to public sewer when it is feasible at reasonable cost. Otherwise an onsite system is acceptable if it works properly and meets local health department requirements; if it is not sufficient and no sewer is available, the property is rejected unless the system is repaired or replaced.

VA training material for appraisers and lenders says septic inspections are generally not required unless the appraiser notes a specific problem, usually odor or seepage, though some states require them regardless. This comes from a 2017 VA training deck; the controlling VA Lenders Handbook chapter could not be read.

• Licensed inspectors must send reports to DHSS, the local authority, the requesting party and the owner within 30 days (19 CSR 20-3.070(10)).
• Owners are not obliged to hire the same licensee for repairs or re-inspection (19 CSR 20-3.070(10)(A)10).
• Check with the lender to learn which type of assessment is required, if any.
• A VA Notice of Value may require evidence from the local health authority that an individual sewage disposal system is acceptable.

Sources: Missouri DHSS, Onsite Wastewater Frequently Asked Questions; Missouri DHSS, Onsite Wastewater Treatment System Inspections Versus Evaluations; HUD Handbook 4000.1, FHA Single Family Housing Policy Handbook (Update 18 redline, last revised 8/12/2026), II.D, Onsite Sewage Disposal Systems; VA Loan Guaranty training slides, Notice of Value Conditions (April 12, 2017)

Aerobic systems and maintenance contracts

Missouri treats aerobic treatment units as basic systems that must meet NSF Standard 40, have at least 120 gallons per bedroom per day (minimum 500 gallons) of capacity, and discharge to a full-size soil absorption system. The state rule says aeration units should be inspected at least once a year and pumped when solids build up, and that management arrangements are recommended, not required; all systems must be run to the manufacturer's or designer's specifications. We found no statewide maintenance-contract mandate, but local ordinances may add one.

• No reduction in absorption field size is allowed because an ATU is used (19 CSR 20-3.060(4)(E)4).
• ATUs should not be used where the home may sit unused for more than five days at a time (19 CSR 20-3.060(4)(E)1).

Sources: 19 CSR 20-3, Missouri Code of State Regulations, DHSS General Sanitation (9/30/20 compilation), 19 CSR 20-3.060(4)(E)5; Missouri DHSS, Onsite Wastewater Treatment Systems

Pumping and septage disposal

Missouri sets a pump-when-needed rule rather than a calendar interval: yearly inspections are recommended, and the tank must be pumped when the scum layer is within 3 inches, or the sludge within 8 inches, of the bottom of the outlet device. Hauled sewage must go to a municipal sewage treatment plant able to take it or be removed by a septic cleaning business that disposes of it properly. Land application of domestic septage falls under DNR general permit MO-G821000, capped at 10,000 gallons per acre per year.

EPA's SepticSmart guidance says a typical household system should be inspected at least every three years by a professional and the tank typically pumped every three to five years, while alternative systems with pumps, float switches or mechanical parts should be inspected about once a year under a service contract. Pump when the scum bottom is within 6 inches of the outlet, the sludge top is within 12 inches of it, or sludge and scum fill more than 25 percent of the liquid depth. Care comes down to four elements: inspect and pump, use water efficiently, dispose of waste properly and maintain the drainfield.

• Owners need no permit or registration to clean their own system (RSMo 701.055(2)).
• DNR general permit MO-G821000 is effective Dec 1, 2022 through Nov 30, 2027.
• Pumping frequency depends on household size, total wastewater, volume of solids and tank size.
• Flush only human waste and toilet paper; avoid grease, chemical drain openers, wipes and heavy garbage disposal use.
• Do not park or drive on the drainfield, keep roof drains and sump pumps away, and plant trees at a safe distance.
• Keep maintenance records and the sludge and scum readings from each service visit.
• SepticSmart Week is held the third week of September each year.

Sources: 19 CSR 20-3, Missouri Code of State Regulations, DHSS General Sanitation (9/30/20 compilation), 19 CSR 20-3.060(4)(D); Missouri DNR, Land Application of Domestic Wastewater Septage (general permit MO-G821000); US EPA SepticSmart, How to Care for Your Septic System; US EPA, SepticSmart Week

Setback distances

Missouri's Table 1 (19 CSR 20-3.060(1)(D)) puts the sewage tank 50 feet and the disposal area 100 feet from a private well, both 300 feet from a public well, and both 10 feet from property lines. Classified streams, lakes and impoundments need 50 feet, and sinkholes 50 feet from the tank and 100 feet from the disposal area; counties with ordinances may require more.

• Private water supply well: tank 50 ft, disposal area 100 ft, lagoon 100 ft.
• Public water supply well: 300 ft for all.
• Spring: tank 50 ft, disposal area 100 ft, lagoon 100 ft. Cistern: 25 ft for all.
• Classified stream, lake or impoundment: 50 ft for all. Stream or open ditch: 25 ft for all.
• Property lines: tank 10 ft, disposal area 10 ft (25 ft downslope recommended initially; repairs may be allowed to 10 ft), lagoon 75 ft.
• Building foundation: tank 5 ft, disposal area 15 ft. Basement: tank 15 ft, disposal area 25 ft.
• Edge of surficial sinkholes: tank 50 ft, disposal area 100 ft, lagoon 500 ft.
• Unplugged abandoned wells or wells with under 80 ft of casing: 150 ft from all.
• Values read from the Table 1 image in the rule PDF.

Source: 19 CSR 20-3, Missouri Code of State Regulations, DHSS General Sanitation (9/30/20 compilation), 19 CSR 20-3.060(1)(D)

Help paying for a failing system

Missouri DNR's Clean Water State Revolving Fund On-site Wastewater Treatment System Grant passes money through nonprofits to help single-family homeowners in selected nutrient-impaired watersheds repair or replace failing systems or connect to sewer, regardless of lot size. DNR offered grants of up to $3 million per nonprofit, and the application period for nonprofits closed June 30, 2026; homeowners apply through the selected nonprofit.

USDA's Section 504 Home Repair program (7 CFR 3550 Subpart C) helps very low-income owner-occupants in rural areas repair their homes: loans at 1 percent for 20 years, and grants for owners 62 or older that may be used only to remove health and safety hazards. Lifetime grants are capped at 10 percent, and total loans at 20 percent, of the national average area loan limit, and a grant must be repaid in full if the home is sold within 3 years.

• USDA Section 504 home repair loans (1 percent, 20 years) and grants for owners 62 and older can pay to remove health and safety hazards; see shared.usda_section_504.
• DNR Financial Assistance Center: 573-751-1192, fac@dnr.mo.gov.
• Up to $125,000 more may support program administration and technical assistance to homeowners.
• Applicants must own and occupy the home, have income under the very low-income limit and be unable to get credit elsewhere.
• Elderly families must use net assets above $20,000 (others above $15,000) toward the cost.
• Loan and grant funds may pay reasonable connection fees for utilities such as water and sewer (3550.102(d)(3)).
• The dollar caps published on USDA's program page could not be read (see unverified).

Sources: Missouri DNR, CWSRF On-site Wastewater Treatment System Grant; 7 CFR Part 3550 Subpart C, Section 504 Rural Housing Loans and Grants (eCFR), 3550.101

Reporting a failing system

File a complaint through the DHSS Onsite Wastewater complaints page, which lists the local authority to contact for each county. DHSS must investigate written or verbal complaints, handing them to a county with its own equal or stricter ordinance and acting itself if no report comes back within 30 days. A county or DHSS can require an owner to abate a nuisance or repair a malfunctioning system within 30 days of notice.

• Complaints about city sewers and wastewater treatment plants go to Missouri DNR.
• Discharging wastewater to a road ditch or onto the ground is not legal (DHSS FAQ).

Sources: Missouri DHSS, Onsite Wastewater Complaints; 19 CSR 20-3, Missouri Code of State Regulations, DHSS General Sanitation (9/30/20 compilation), 19 CSR 20-3.015(7); RSMo 701.037, 701.037(4)