Frequently Asked Questions

Frequently Asked Quesitons

What is an onsite sewage system or onsite wastewater treatment system (OWTS)?

Onsite wastewater treatment systems are sometimes referred to as "septic systems." These 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.

How do I determine if jurisdiction falls under Department of Health and Senior Services (DHSS) or Department of Natural Resources (DNR)?

The following link on Department of Natural Resources website will provide you with the information necessary to determine jurisdiction based on the facility type and method of wastewater treatment.

Is there a minimum lot size requirement for an OWTS?

Where the state onsite laws apply, it does not set a minimum lot size. Counties with a wastewater ordinance, may have restrictions. Additionally, some subdivisions may have a minimum approved lot size for onsite systems. DNR provides written approval for the method of wastewater treatment for some subdivisions. Typically lagoons require more land due to greater setback requirements

Do I need a permit to install an OWTS?

A construction permit is required to install or repair an onsite system on any residential property less than three 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 all other onsite systems that serve non-residential structures.

How does a property owner know what type of OWTS 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, 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.

Why do I need a soil report?

Soil reports provide information about the soil characteristics and site. Installing the correct type of onsite system protects public health and helps maximize the longevity of the onsite system.

Visit our homepage and click “Find a Professional” for a list of registered soil evaluators (and other professionals).

What is the difference between a basic and advanced system?

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, pressure distribution to conventional sized fields, modified shallow conventional systems and other systems using fill soil.

Visit our homepage and click “What is an Onsite Wastewater Treatment System?” for more information.

Can I, as a homeowner, install my own OWTS?

In some instances, homeowners may install their own system. However, you must check with the local permitting authority. Additionally, a construction permit may be required. We strongly encourage you to work with a registered installer. Visit our homepage for permitting information or to find a professional.

Is it legal for wastewater to discharge into a road ditch or onto the ground?

No. Your system cannot pose a threat to public health or to the environment.

What should I do with an abandoned OWTS on my property?

Over time the chance of a buried tank or access lid collapsing increases, making it a safety hazard. Abandoned tanks can be a health hazard if not properly decommissioned. Generally no permit will be necessary to properly abandon a sewage tank; however, you should contact the county authority before you begin to be sure. Check with your local permitting authority for requirements. If there are no local requirements; have the tank emptied of all contents by a professional waste hauling company. You may then: 1) have the sewage tank crushed in place and then backfill the area; 2) have the empty tank completely filled with sand or gravel, remove risers, cover openings and then backfill the area; or 3) 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.

Does the law require an inspection/evaluation of an OWTS prior to a real estate transaction?

No. However, if a lender or buyer requests an inspection/evaluation, it must be conducted by a licensed individual. Some counties may require an onsite system inspection/evaluation for every real estate transaction. Check with the local permitting authority.

What if my OWTS does not meet the inspection/evaluation requirements?

The inspection/evaluation determines if the system meets the current state standards and if it is operating properly. It is informative to all parties involved in the real estate transaction. State law does not require the owner to correct items noted. However, parties involved in the transaction may require items to be fixed. Check with the local permitting authority for additional requirements.

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Frequently Asked Quesitons