Oklahoma homes and businesses utilize on-site sewage systems, commonly referred to as septic systems, to ensure that sewage is properly treated in order to protect the waters of the state, the public health, and the environment.
DEQ Rules and Regulations: Chapter 252:641 Individual and Small Public On-Site Sewage Treatment System establishes requirements for the design, construction, installation, and operation of individual and small public on-site sewage treatment systems.
Effective November 1, 2025, individuals not certified through DEQ may only install one (1) on-site sewage treatment system per calendar year.
The Report for On-Site Sewage, commonly referred to as the 581, determines what types of on-site systems are allowed for the property. The report also describes the minimum dispersal requirements based on the size of the residence or daily flow of a small public system.
A minimum of three holes or pits are dug in the dispersal area to provide a comprehensive description of the soil's texture. The results are used to determine all allowable system types (conventional subsurface, aerobic with spray or drip irrigation, lagoon).
Soil Profile Tests may only be conducted by DEQ or DEQ-Ceritified Soil Profilers.
A minimum of three holes or pits are dug in the dispersal area. These holes are presoaked and filled with water to maintain a minimum depth of 12 inches for at least 24 hours. Following the presoak period, the percolation rate will determine if a conventional system is permissible and will determine its dispersal requirements.
Percolation tests may only be used to identify dispersal sites for conventional subsurface systems. Percolation tests may not be performed in scenic river corridors or in a water body protection area.
Percolation tests may only be performed by individuals registered through the Department of Health.
Property location and other details are used to determine allowable system types and minimum dispersal requirements. Designs are always based on Group 5 soil (the highest clay content).
Design Only may only be used for aerobic with spray irrigation or lagoon systems.
Before installing a new or modifying an existing on-site sewage treatment system, an Authorization to Construct (ATC) must be purchased and issued by DEQ.
After the ATC is purchased, it is assigned to the local DEQ Environmental Specialist (ES), based on the location of the property, for review and issuance.
The Report for On-Site Sewage (581) must be reviewed by DEQ before the ATC may be issued.
All new installations or modifications to an on-site sewage system must be inspected and approved by DEQ or installed, self-inspected and approved by a certified installer before the system may be placed into operation.
Final inspections are documented on DEQ Form 641-576. The information provided must clearly identify all system components, their location on the property, and minimum required separation distances per Chapter 641.
Final inspections performed by a certified installer must be submitted to DEQ within 15 days of completion.
The design and installation of an on-site sewage system is dependent on many factors. The size and shape of the lot, the size of the residence and the results of the soil test. There are instances when a system described in our rules cannot be designed and an alternative on-site system is needed. Alternative systems must be approved by the DEQ prior to the system installation. For additional information concerning alternative systems and the application/approval process for alternative systems, please contact your local DEQ representative or (405)702-6100.
When an on-site system is properly designed, installed, and maintained, it serves as an effective and economic treatment system. More times than not, however, the on-site system is installed and forgotten. Maintenance is the homeowner’s responsibility and is the key to avoid system malfunctions and possible costly repairs.
The type and frequency of maintenance required for your on-site system depends on the type of system. So, the first step of system maintenance is to know the type of system that serves your home or business. Listed below are descriptions for the types of on-site systems. Click on the type of system for a detailed explanation of specific maintenance items.
If you are still unsure about the type of system you have after reading the descriptions below, then contact your local DEQ office for assistance at (405)702-6100.
