Who may install a septic system in Missouri
Missouri does not license septic installers the way it licenses some trades. It registers them, and the statute is short about it: any person installing onsite sewage disposal systems shall be registered to do so by the Department of Health and Senior Services. Registration is a real requirement with a real consequence, and checking it takes one phone call or one look at a card. It is also a check almost nobody makes.
Source: Section 701.031, Revised Statutes of Missouri, read 2026-08-26.
Registered or licensed, and does the difference matter?
Registered. The distinction is not pedantry: a licence usually implies an examination, a bond and a disciplinary body, and a Missouri onsite registration is built differently. A person may not represent themselves as a registered onsite sewage disposal system contractor in this state unless they are registered by a county or by the department.
That also means this site will never tell you a contractor is licensed, and you should be wary of anyone in Missouri who says they are. What we route is a request to an independent local contractor. Confirming their registration is a step you take yourself, and the next capsule is how.
Source: Section 701.053, Revised Statutes of Missouri, read 2026-08-26.
How do I check whether an installer is registered?
Two ways, and they complement each other. The state publishes a list of registered onsite wastewater installers, filterable by county and carrying business names and phone numbers. Start there. But read the state's own caveat before you draw a conclusion from an absence: the list is not all inclusive, because being on it is optional.
So a contractor missing from the list is not proven unregistered. To settle it, ask to see their registration identification card, or call the Onsite Wastewater Treatment Program on (573) 751-6095 and ask. Both are normal requests and any registered installer expects them.
Source: Missouri Department of Health and Senior Services, registered OWTS installers list, read 2026-08-26.
What does a contractor have to do to get registered?
Complete training. To qualify for registration a contractor must successfully complete the educational training program provided by the department, or training offered by a county that the department has certified and that has an ordinance or regulation mandating contractor training. The statute sets out the training route and does not state an examination, an experience requirement, an insurance requirement or a fee amount.
One useful consequence: a registration issued by a county in compliance with the statute counts as a state registration and is valid in every political subdivision of the state. A contractor registered through one county is not limited to working in it.
Source: Section 701.053, Revised Statutes of Missouri, read 2026-08-26.
Does using a registered installer actually change anything?
Yes, and this is the part worth knowing before you choose. The inspection burden on your system depends on who built it. The city, county or department inspects, in the aggregate, up to sixty percent of systems constructed, modified or repaired by registered contractors, and at least seventy-five percent of those built by persons who are not registered.
Read that as what it is: the state treats unregistered work as needing more scrutiny, and it has written that judgment into how often the authority turns up. If you are weighing a cheaper quote from someone who is not registered, that is the trade you are actually making.
Source: Section 701.043.3, Revised Statutes of Missouri, read 2026-08-26.
What is the basic and advanced registration split?
Missouri issues onsite installer registration at a basic and an advanced level, and the advanced level exists because some system types need it. If your soil evaluation has pushed the design toward an alternative system rather than a conventional trench field, the question to ask is not only whether your installer is registered but whether they are registered at the level your system requires.
Source: Missouri Department of Health and Senior Services, Onsite Wastewater Treatment, read 2026-08-26.
Once my system meets the state standard, can the county still add requirements?
Not at the approval stage. If a city, county or the department determines that a system meets the requirements of the state standards, it may not impose any additional requirement before that system is approved for operation.
That sits alongside a county's power to adopt standards of its own that are more restrictive than the state's, so the practical reading is about timing: the place to discover a county's added requirements is at design and application, not at final approval. Ask early what your county requires beyond the state standard.
Source: Section 701.043.2, Revised Statutes of Missouri, read 2026-08-26.
Four questions before you sign anything
- Are you registered with DHSS, and may I see the card.
- Basic or advanced, and is that the level this system type needs.
- Who is pulling the permit, and with which agency in this county.
- Who did the soil evaluation, and are they on the state evaluator list.
Then see how the permit itself works and who issues it in your county.
Get a free quote from a Missouri septic contractor
Tell us the county and the job. No email needed.
A marketing service, not a licensed contractor. Septic work is performed by independent local contractors.
Need the job done, not just the rule explained
Your request goes straight to an independent local septic contractor serving your Missouri county, usually within about an hour during the day, not a national lead list.
Tell us the county and the jobLast reviewed 2026-08-26.