Frequently Asked Questions

Onsite Wastewater Treatment

What is an onsite sewage system or onsite wastewater treatment system (OWTS)?
What is the minimum lot size required for an onsite sewage system?
I need a soil test report. Who do I contact to do a soil test?
Can I, as a homeowner, install my own onsite sewage system?
Who is responsible for maintenance of my onsite system?
Is it legal for my home's aerator system to discharge to a road ditch?
If I buy a home and move it onto a property with an existing system, can I use the existing system?
Does the state law require an inspection or evaluation of my onsite sewage system before I sell my home?
Where can I find a list of basic and advanced registered installers?
What system and components are considered basic and advanced?
How does a homeowner know what type of onsite system is needed?
What agency do I contact if my neighbor(s) and I want to build a lagoon to serve more than one home?
Do I need a permit to install an onsite system?
How much does a construction permit cost?
What should I do with sewage tank on my property that is no longer in use?

Onsite Sewage Professionals FAQs

What is an onsite sewage system or onsite wastewater treatment system (OWTS)?
Onsite systems are sometimes referred to as "septic systems." Onsite sewage systems treat and dispose of domestic sewage on the property where it is generated. One example is a septic tank and soil absorption system. Another example is a lagoon serving a single-family residence. Missouri's onsite sewage law covers systems with a daily flow of 3,000 gallons or less.

What is the minimum lot size required for an onsite sewage system?
Where the state onsite sewage law applies, it does not set a minimum lot size. Some subdivisions may have a minimum approved lot size for onsite systems. The Missouri Department of Natural Resources (MDNR) regulates subdivisions.

I need a soil test report. Who do I contact to do a soil test?
There are two types of soil tests that can be accepted, percolation tests or soil morphology evaluations. Usually, soil morphology evaluations are preferred because they provide more information for system design. Check with the local onsite sewage authority to find out what test will be accepted. Soil evaluator lists can be found through links from the Onsite Professionals page. A list of persons who can do percolation tests is available from the Missouri Department of Health and Senior Services or the local authority.

Can I, as a homeowner, install my own onsite sewage system?
Yes, homeowners may install their own system. However, you must obtain a construction permit and follow the law and the construction standards. We recommend you contract with a registered installer.

Who is responsible for maintenance of my onsite system?
As the system owner, you are responsible for its maintenance. If you don't take care of your system, it may not properly treat wastewater from your home or business. This could put your family's or neighbor's health at risk. Lack of maintenance could also lead to more costly repairs in the future. The system manufacturer or installer may provide service for a period of time. If not, or after that period, a maintenance agreement is recommended.

Is it legal for my home's aerator system to discharge to a road ditch?
No. Although, if you have that type of system and it existed before January 1, 1996, it is exempt from inspection. You may not have to repair it unless there is a complaint from a neighbor or other affected person. However, your system could pose a threat to the health of your family and community, and to the environment. You should consider upgrading your sewage system if it discharges on the ground surface.

If I buy a home and move it onto a property with an existing system, can I use the existing system?
Unless you make major changes to the existing system, no permit is required to connect a new home. However, if the system is too small or poorly constructed it may not work right. If it fails, discharges onto the ground surface, or creates a nuisance or health hazard, and an affected person complains, you will be required to bring the system up to standards.

Does the state law require an inspection or evaluation of my onsite sewage system before I sell my home?
No. However, if a lender or buyer requests an inspection/evaluation, it must be conducted by a licensed individual. (Some counties do require an onsite system inspection for every sale.)

Where can I find a list of basic and advanced installers?
Registered Installer lists can be found through links from the Onsite Professionals page. However, individuals may request that their name not be published on our website. If you have any inquiries, you may contact us (see information on right side of page).

What systems and components are considered basic and advanced?
Basic systems and components consist of sewer lines, septic tanks and aerobic treatments units (ATUs), gravity distribution, gravity laterals, dosed gravity systems, shallow placed gravity systems, lagoons, holding tanks and privies.
Advanced systems and components include sand filters, bio-filters, constructed wetlands, sand mounds, low-pressure pipe (LPP) distribution, subsurface drip distribution (SDD), pressure distribution to conventional sized fields, modified shallow conventional systems and other systems using fill soil.
More information about these systems and components is available on our systems page.

How does a homeowner know what type of onsite system is needed?
Several factors should be considered when choosing the type of onsite system for a site including: soil/site limitations, available space, operation and maintenance (O & M) requirements, initial as well as O & M costs, landscape disturbance, and the owners' preferences and ability to manage the system. Of these considerations, often the most limiting is the soil resource or site and space limitations.

What agency do I contact if my neighbor(s) and I want to build a lagoon to serve more than one home?
You should contact the Missouri Department of Natural Resources (MDNR) regional office. MDNR regulates lagoon systems that serve businesses or more than one family. You should also consider an onsite or cluster system using soil treatment and dispersal.

Do I need a permit to install an onsite system?
A construction permit is required to install or repair a system on any residential property less than three (3) acres. (This exemption does not apply in some counties; check with the county authority.) Regardless of the size of the property, a permit is necessary for systems that serve businesses.

How much does a construction permit cost?
The application fee for a state permit it $90.00. Jurisdictions with local ordinances may charge higher permit fees. The application and proposed system layout must be reviewed and approved before a permit can be issued. Payment of the application fee does not guarantee you will receive a permit.

What should I do with sewage tank on my property that is no longer in use?
Although sewage tanks are generally buried, over time the chance of the tank or an access lid collapsing increases making it a safety hazard. Also, if a tank is abandoned in a careless manner it could be a health hazard. If the tank is to be abandoned when a replacement system is installed or when a connection is made to a central sewer, check and follow requirements of the design if any. Generally no permit will be necessary to properly abandon a sewage tank; however, you should contact your local health agency before you begin to be sure.

When there are no local requirements or other guidance, you should first have the sewage tank emptied of all sewage waste. This should be done by a professional waste hauling company that disposes of the waste at a permitted land application site or wastewater treatment facility. You have some options from there: 1) you can have the sewage tank crushed in place and then backfill the area; 2) you can have the empty tank completely filled with sand or gravel, remove risers, cover openings and then backfill the area; or 3) you can have the empty tank removed from the property and disposed at a landfill provided the landfill can accept it, and then backfill the area. After backfilling, grade the area to shed water and seed with grass.