Septic Systems

In areas where public sewer is not available, homeowners must have septic systems installed on their property that will treat wastewater coming from their home.

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Latest News

Reminder to Submit Complete Septic Applications, Comply with Septic Standards, and Maintain Professional Communications

Published on October 12, 2020

Septic Professionals: This message is intended as a reminder to please submit complete septic applications in accordance with county standards including the OWTS Manual v7.0, policies and procedures, and published guidance documents as well as to encourage and promote professional communications.

Septic Permitting Updates Messages

Published on December 31, 2019

Permit Sonoma is implementing a variety of septic permitting improvements in an effort to assist customers comply with the recently adopted Onsite Wastewater Treatment System (OWTS) Manual version 7.0 and to make our permitting processes clearer and more efficient.

Septic Permitting Changes Now in Effect

Published on August 16, 2019

The Director of Permit Sonoma hereby adopts the County of Sonoma’s Onsite Wastewater Treatment System (OWTS) Manual, version 7.0, dated As of August 15, 2019, the Sonoma County Onsite Wastewater Treatment System (OWTS) Manual version 7.0 is in effect.  Customers are hereby advised that any septic applications will be required to comply with the provisions of the OWTS Manual version 7.0.  Customers are further advised of the following updates to Permit Sonoma’s permitting procedures...

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Types of Septic Systems

There are two types of septic systems:

Standard Onsite Wastewater Treatment System (OWTS)

A type of OWTS consisting of a septic tank for primary treatment of sewage, followed by a system of drainfield trenches for subsurface dispersal of effluent into the soil. A standard OWTS may utilize gravity flow or a pump system to convey effluent from the septic tank to the drainfield.

Non-standard Onsite Wastewater Treatment System

A type of OWTS that utilizes a method of wastewater treatment that may or may not include a conventional septic tank and/or method of wastewater dispersal other than a conventional drainfield for the purpose of producing an equal to or greater quality wastewater effluent and improved performance of and siting for effluent dispersal than a standard OWTS. There are two types of non-standard systems. There are two types of non-standard OWTS:

  • Alternative OWTS: an approved non-standard OWTS that has demonstrated in the non-standard Experimental phase to function in such a manner as to protect water quality, preclude health hazards and nuisance conditions and capable of producing an equal to or greater quality wastewater effluent and improved performance of and siting for effluent dispersal than a standard OWTS. Examples of these are pretreatment units, mound OWTS, shallow trench pressure distribution OWTS, at-grade OWTS, shallow in ground OWTS, bottomless sand filter OWTS, and subsurface drip dispersal OWTS.
  • Experimental OWTS: a non-standard OWTS deemed conditionally acceptable by the Regional Water Quality Control Board, subject to increased performance monitoring and evaluation, prior to acceptance as an approved non-standard Alternative OWTS. Examples of these are bottomless sand filter OWTS and gravel-less pressurized dispersal channels.

Cottage Foods Septic Requirements

Cottage Food Operation Permit Requirements for Operators on Septic Systems

This guidance document is for Cottage Food Operations that are connected to an onsite septic system for liquid waste disposal, verses a county or city sewer system.

Cottage Food Operation (CFO) is governed under the California Homemade Food Act and it allows for certain types of food to be prepared and sold from a home kitchen operated food facility.   Governor Brown signed the California Homemade Food Act into law on September 21, 2012.

View the Requirements

Site Evaluations, Testing, and Monitoring

Properties with septic systems may need the following evaluations, testing, and monitoring activities. 

Site Evaluation

Before you apply for a septic permit you will need a soils profile evaluation and you may need percolation and groundwater testing. 

  • Soils Profile Evaluation: Soil profile holes for the Preliminary Site Survey Soil Profile Evaluation are for the purpose of observing soil structures, texture, formations; the presence of seasonal groundwater; impervious rock formations, etc. Profiles are essential in the evaluation of any parcel for soil suitability for private sewage dispersal systems.
  • Percolation Test: A test conducted to determine the permeability or percolation quality of the soil in an area proposed for sewage dispersal.
  • Wet Weather Percolation & Groundwater Testing: Required when a new or replacement septic system is installed, as well as if the septic system is located in a basin area with slopes of 0% to 5% or is in a defined geographic area that has received 50% of seasonal rainfall.

Monitoring Non-Standard Septic Systems

Owners with non-standard septic systems are required to participate in the County’s operational permit monitoring program.

Recommended Septic Maintenance and Reminders

The following activities are recommended to properly maintain your septic system: 

  • Clean Sump filter annually.
  • Pump septic tank every 3-5 years depending on use.
  • Purge and balance system annually by a C42 or Engineering Contractor familiar with these systems.
  • Switch diversion valve (if you have one) annually, or as specified on approved septic plans.
  • For those with pre-treatment units requiring sampling for analysis, see #7 on supplemental agreement, provide results to our office once per year for at least 2 years. Samples may be taken from sump tank.
  • Keep expansion areas unencumbered.

Resources for maintaining septic systems and vegetative cover: 

Contact Information

Contact Well & Septic by Phone
2550 Ventura Avenue
Santa Rosa, CA 95403
38.465074, -122.723705

Well & Septic Maps

Well & Septic Districts Map

Well and Septic Districts Map

Map of Well & Septic's environmental health districts within Sonoma County.