About Onsite Wastewater Treatment Systems (OWTS)

Overview: Onsite Wastewater Treatment Systems (OWTS), also known as septic systems, are used to treat wastewater that is contaminated by human use, from a home or business, and then released into the environment. OWTS are underground structures that treat and dispose wastewater, typically from homes and businesses in suburban and rural locations. Instead of the wastewater being transported to a wastewater treatment plant, the wastewater is treated on-site.

Conventional OWTS consist of a septic tank and a drainfield system. Wastewater from a house or business drains into a septic tank that is buried underground. The first step in the treatment process is for the solid material in the septic tank to settle on the bottom of the tank, while oil and grease float to the top. The material from a home or business is known as effluent, liquid waste, or sewage discharge. A compartment in the septic tank stops the solid and greasy waste from leaving the tank and the remaining liquid then moves into a drainfield area or distribution system, which is the second step in the treatment process. When the wastewater moves into the drainfield, it filters through the soil, naturally removing any remaining bacteria and is eventually released into the groundwater.

Regulations: Regulations for wastewater treatment systems are created to protect human health and the environment. The State OWTS Policy, required by Assembly Bill (AB) 885, sets standards for wastewater treatment and monitoring requirements. It also authorizes the State, through the Regional Water Boards to authorize local governments to approve OWTS for domestic wastewater through a Local Area Management Program (LAMP). The Los Angeles County Code defines the guidelines and regulations for efficient systems to appropriately dispose of waste through OWTS. If residents and businesses do not follow regulations for wastewater treatment systems, polluted water could be released into the environment. This water may have higher levels of contaminants in it than regulations allow, which may pollute our natural bodies of water where we recreate, swim, or fish. As a result, it may harm animals and the nearby community.

About Non-Conventional Onsite Wastewater Treatment Systems (NOWTS)

Overview: NOWTS are onsite wastewater treatment systems that use a regular septic tank, as well as one or more additional treatment components to treat the effluent before the remaining liquid moves into a drainfield area or distribution system. The additional treatment components may include systems to reduce the nitrogen concentration of the effluent, provide disinfection, or both. High nitrogen concentrations in bodies of water may harm the overall environment where the wastewater is being released.

When there is an excess of nitrogen in groundwater and that groundwater is used for drinking water it can be especially harmful to human infants and young livestock. This can lead to problems with blood circulation in the body, especially for infants under age 4, whose bodies are not yet developed enough to process elevated nitrogen, which causes a condition known as "blue baby syndrome."

Regulations: The Los Angeles County Code defines the guidelines and regulations for wastewater treatment systems to appropriately dispose of waste. Home and business owners that meet the guidelines set by LA County, may be approved for the installation of a conventional onsite wastewater treatment system. In some areas of the County, the rate at which water is absorbed in the soil exceeds guideline standards and local regulations. In these areas, property owners may apply for approval of a non-conventional wastewater treatment system to ensure the proper treatment of wastewater.

The Onsite Wastewater Treatment Program of the Environmental Health Division reviews proposed Onsite Wastewater Treatment Systems designs, work plans, required covenants, historical records, and performs site and installation inspections prior to issuing final system design approvals. System design approvals may be submitted to your local Building and Safety Department to obtain building permits for proposed projects.

Property owners must submit Conventional or Non-Conventional Onsite Wastewater Treatment System plans to any Onsite Wastewater Treatment Program field office or to the Environmental Health Division Headquarters for review. Once approved, stamped and approved plans are then provided to the applicant.

Responsibilities of the Onsite Wastewater Treatment Program include reviewing and approving plans for Conventional and Non-Conventional Onsite Wastewater Treatment Systems within unincorporated areas of Los Angeles County and designated cities that have signed the County’s LAMP MOU.

A cesspool is a lined pit that receives and stores sewage directly from the house, without the use of a septic tank. The installation of new cesspools is prohibited in California.

For properties with existing cesspools within the Eaton Fire Burn Area:
In coordination with the Los Angeles Regional Water Quality Control Board, continued use of existing cesspools will be permitted during the reconstruction period under the following conditions:

  • Functionality Verification: Each cesspool must be demonstrated to be functioning through a percolation test conducted by a Qualified Professional (QP). Testing must follow the procedures outlined in the County of Los Angeles Local Agency Management Program (LAMP) and meet the minimum percolation rate criteria specified in Table 3-2 of the LAMP. The County Department of Public Health will review and approve all test results.
  • No Increase in Wastewater Flow: Property owners may not increase potential wastewater flow to an existing cesspool. This includes any reconstruction that adds bedrooms, bathrooms, or bedroom equivalents, such as Accessory Dwelling Units (ADUs). Reconstruction plans must reflect the number of previously permitted bedrooms and bathrooms, and any changes require prior approval from the Public Health Department.

If a property owner wishes to rebuild with additional bedrooms or bedroom equivalents, the cesspool must be upgraded to a septic system or connected to the public sewer if located within 200 linear feet. Approval must be obtained from the Public Health Department if upgrading to a septic system.

These temporary allowances are consistent with the County's plan to phase out cesspools. As long as these conditions are met, no additional approvals (such as Waste Discharge Requirements or waivers) will be required from the Los Angeles Regional Water Quality Control Board.

The Los Angeles Regional Water Quality Control Board is developing a long-term plan to phase out cesspools in the Eaton Fire area, which may include extending public sewer service. If a sewer extension is determined to be infeasible within three years, the Los Angeles Regional Water Quality Control Board will reassess whether continued cesspool use is feasible or if upgrades to an approved onsite wastewater system are required. Any requirements to upgrade will be conditional on funding being available for either installation of public sewer or upgrading to a septic system.

Cesspool Application Submittal Requirements

Document Submission via EPIC-LA

All required documents must be uploaded through EPIC-LA, the County's electronic permitting and plan review system, for review and approval.

Required Submittal Documents

  • Percolation Report
    • Conducted by a Qualified Professional (QP)
    • Must meet LAMP standards and include results that meet or exceed the minimum percolation rate criteria as specified in Table 3-2 of the LAMP.
    • The percolation test must comply with the Environmental Health Onsite Wastewater Treatment Program's Professional Guidelines Requirements and Procedures for Conventional and Non-Conventional Septic systems.
  • Site Plan
    • Stamped and signed by the QP
    • Must clearly identify the location of the existing cesspool, setbacks, structures, and site drainage.
  • Floor Plan
    • Must reflect only the number of bedrooms and bathrooms that were previously permitted.

Review Process Notes

  • A review sheet indicating incomplete or missing documents will be uploaded to EPIC-LA if corrections are needed.
  • Once all requirements are met, the approved plan will also be uploaded to EPIC-LA for retrieval by the applicant.

Please note: For faster review and approval, ensure that all documents are complete, signed, and stamped where required, and accurately uploaded through EPIC-LA.

Additional Documents

Los Angeles County Department of Public Health (LACDPH) reviews and approves OWTS under the provisions of the LAMP to residents of unincorporated county areas and contracted cities. Cities must adopt the appropriate sections of the Los Angeles County Health and Safety Code (Title 11) and the Los Angeles County Plumbing Code (Title 28) before entering a Memorandum of Understanding (MOU) with the County to be covered under the LAMP’s provisions and restrictions. For more information regarding the LAMP, please visit our LAMP page. LAMP cities that have an MOU with the County include:

  • Agoura Hills
  • Bradbury
  • Duarte
  • Glendora
  • Hidden Hills
  • La Canada Flintridge
  • La Habra Heights
  • La Verne
  • Lomita
  • Lancaster
  • Palmdale
    • ssss
  • Palos Verdes Estates
  • Rancho Palos Verdes
  • Rolling Hills
  • Rolling Hills Estates
  • Santa Clarita

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Report a Problem

If you have questions or concerns about conventional or non-conventional onsite wastewater treatment systems, contact the Onsite Wastewater Treatment Program at (626) 430-5380. For complaints, contact the Environmental Health Call Center at (888) 700-9995 or File a Complaint Online.

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