Introduction

Oklahoma is a state of great beauty and ecological diversity, attracting many people to build or buy a home in the state. However, Oklahoma’s great diversity means homeownership can look quite different across cities, countryside and various ecological regions of the state. One important feature of a home and its property that can vary by location is the availability of public water and wastewater services. How wastewater generated within the home will be treated is an often-overlooked necessity. While public wastewater services are more common in municipalities, the need for a private wastewater treatment system, often called a septic system, can occur in Oklahoma’s urban areas as well as in rural areas.

While often overlooked, septic systems play a critical role in the overall functionality of a home, and there are many important considerations regarding septic systems. Three key things to remember with septic systems are 1) they are expensive to install, 2) they need care and maintenance for proper functionality and 3) there are rules that govern their installation and maintenance. This fact sheet reviews the rules you need to know regarding site and soil restrictions, securing an installation permit and installation and maintenance of septic systems. For additional details about maintenance of septic systems and the various types of systems permitted in Oklahoma, refer to Extension fact sheets PSS-2914, Keep Your Septic System in Working Order and PSS-2913, On-site Wastewater Treatment Systems Permitted in Oklahoma.

In Oklahoma, rules that pertain to septic systems are conveyed in Title 252 of the Oklahoma Administrative Code Chapter 641, “Individual and Small Public On-Site Treatment Systems.” This Code was used as a reference in preparing this fact sheet. While much of this fact sheet is written in a simplified question-and-answer format, some sections are reproduced almost verbatim from the Code.

Site Requirements and Restrictions

Is There a Minimum Lot Size Requirement?

If a Public Water Supply (water from a city or rural water district) is used, the minimum lot size requirement is typically 0.5 acres. If a private water well is used, then the minimum lot size requirement is typically 0.75 acres.

Where Can The Septic System Be Installed?

All components of the septic system, including tanks, pumps, dispersal fields and collection line(s), need to be installed on the property of the system owner and/or in a dedicated, recorded easement for the installation and operation of the septic system. Keep in mind there are separation distances from objects such as water wells, property lines and buildings, as well as other rules. Specific details on separation distances can be found in Title 252 of the Oklahoma Administrative Code Chapter 641, “Individual and Small Public On-Site Treatment Systems.”

What Is a “Water Body Protection Area” and Is The Property in It?

Oklahoma has designated Water Body Protection Areas (WBPA) on lands located near reservoirs and streams that are impaired or threatened by pollution. To install a septic system within 300 feet of a listed reservoir or stream bed, an addition-al advanced treatment system with a nitrogen-reducing component is required to mitigate pollution. This means the septic system for that area will cost more. To determine whether the property is within the WBPA, check with the local Oklahoma Department of Environmental Quality (DEQ) office. Locations of DEQ offices can be found at Oklahoma DEQ Offices.

How Much Land Area Is Required for the Septic System?

Oklahoma onsite wastewater regulations do not explicitly state a minimum land requirement for a septic system; however, they do provide minimum linear or square footage requirements for various flow rates and systems. This is commonly referred to as “sizing requirement.” These requirements depend on many factors, such as site topography, soil conditions, the size of the dwelling, the number of bedrooms and proximity to WBPAs. To determine the exact area needed for a septic system, the frst step is to conduct a soil test. However, as a rule of thumb, at least 10,000 square feet (or approximately 0.25 acres) should be allocated for the entire septic system. In addition, the area should be accessible to the installer and the equipment needed for earth-working activities related to the installation.

Required Soil Testing

Conducting a soil test is the first step in determining the minimum sizing requirements needed for your septic system.

What Soil Test Needs to Be Performed?

There are two potential options for soil tests: 1) Percolation Test and 2) Soil Profile Description. While they are both used to size septic systems (i.e., to determine the area of soil needed to treat wastewater), they are distinct in methodology. A percolation test serves as an indicator of the rate of subsurface water flow at depths where wastewater is normally applied (e.g., 24-36 inches). A soil profile description determines the suitability of the soil to treat wastewater by examining soil texture (how fine or coarse the soil is) and color at 6-inch depth intervals from the surface down to 48-54 inches or until a limiting layer (i.e., a flow-restricting layer) is found.

Either test can serve as a basis for making septic system-related decisions; however, only a soil profile description can be used in sites located within a WBPA or within two miles of a state-defined scenic river (such as the Illinois River and its tributaries, see Illinois River for more information). It should also be noted that the soil profile description provides more detailed soil information than a percolation test, resulting in more options for potentially suitable septic systems that could be installed.

There are several different types of septic systems permitted for use in Oklahoma (see fact sheet PSS-2913), and the soil testing requirements for each varies. A percolation test, for example, can only be used when planning a conventional subsurface system and cannot be used for planning an alternative type of septic system (such as shallow extended or evapotranspiration/absorption systems). On the other hand, installation of lagoons or aerobic treatment systems with spray irrigation does not require a soil test. Regardless, completing a soil profile description is generally the best place to start when planning for a septic system.

Who Can Perform Soil Tests?

Soil tests can be performed by soil scientists, professional engineers, professional land surveyors, professional sanitarians or professional environmental specialists registered to practice in Oklahoma. The DEQ also employs Environmental Specialists who are Registered Sanitarians and can conduct soil profile descriptions. The DEQ does not conduct percolation tests. Results from these tests are used by installers to design the septic system, which is then submitted to DEQ for approval. A list of certified soil profilers can be found at Soil Profiler List. Note: There are some municipalities in Oklahoma requiring a soil test report before issuing a building permit.

Authorization/Permit to Construct

What Activities Require an Authorization?

All new installations of and modifications to an existing septic system need to have an Authorization/Permit to Construct before work can proceed. Septic system modifications may be needed due to a a) malfunction, b) home renovation leading to an increase in the number of bedrooms, c) an increase in water use due to change in use of a house or building and/or d) the relocation of any component of a septic system that does not fall under the definition of a new installation.

Where and How Can I Get an Installation or Modification Authorization?

DEQ is the permitting and regulatory agency for all on-site septic system-related requests and issues. To apply for a permit, contact your local DEQ office for assistance or find an application online (ECLS Forms). Usually, the installer will process the installation or modification application for you.

Inspections

Who Conducts Inspections, and When Are They Necessary?

If your system is installed, repaired or modified by a non-certified installer, then DEQ personnel are required to visit and inspect the site before any component(s) are backfilled with soil or become operational. However, if your system is installed, modified or repaired by a DEQ-certified installer, then there is no need for an inspection by DEQ, as certified installers are authorized to perform self-inspections of systems. A certified installer can be found at Active Certified Installers.

Who Is Responsible for Arranging a DEQ Inspection?

The installer is responsible for requesting any required DEQ inspection related to an installation, modification or repair. Inspections related to complaints will be managed by the DEQ personnel.

Installation

Who Can Install a Septic System?

It is recommended that you utilize the services of a DEQ-certified septic system installer or your local environmental specialist. A list of DEQ-certified installers can be found at Active Certified Installers or from the local DEQ office. The state of Oklahoma does allow anyone to install on-site septic systems (non-certified installers). However, non-certified installers are limited to only one installation per year. Further, installations done by non-certified installers must be inspected and approved by DEQ personnel before they are backfilled and/or made operational.

Are New Installations Covered by a Mandatory Warranty/Maintenance Period?

Installers are not required to provide a warranty for most types of septic systems; however, if an aerobic treatment system/ unit is installed, then Oklahoma rules require the installer to provide a free, two-year maintenance period. This rule mandates that the installer of an aerobic treatment system inspect and maintain the system at no additional cost to the homeowner for 2 years following the date of installation. Within this period, the installer is required to inform the owner of the operational status and any repairs or replacements performed on the system.

If you buy a house and the aerobic treatment system is still within the warranty period, you are eligible for the warranty until the two-year period expires.

Responsibilities of The Owner

Properly working septic systems will treat harmful pollutants in household wastewater. Improperly functioning systems pose hazards to owners, their neighbors and the environment.

Oklahoma onsite wastewater regulations clearly state the owner of an on-site sewage treatment system shall ensure the system is maintained and operated properly so that 1) sewage or effluent from the system is properly treated and does not surface, pool or flow across the ground or discharge to surface waters, 2) all components of the system including lagoons are maintained and do not leak or overflow and 3) the required security measures are intact (e.g. required fences for lagoons are intact, septic tank lids are intact and properly secured, etc.).

The rules also state that if a septic system malfunctions, the person owning or otherwise responsible for the system needs to take prompt action to repair the malfunctioning system, prevent further violations, and remediate the site. Violations and negligence are subject to enforcement actions and possible penalties.

Contact

For questions or assistance with septic system permits, installation, or compliance, contact your local DEQ office or by calling (405) 702-6100.