Environmental Engineering - Subsurface Sewage


An estimated 40% of Connecticut residents, close to 1.5 million people, live in homes served by on-site sewage systems. The vast majority of these sewage systems are conventional septic systems that are under the jurisdiction of the Local Directors of Health, and are the primary means of sewage disposal in rural and low density suburban areas. Septic systems also serve apartment buildings, schools, restaurants, and other commercial buildings in non-urban areas.   


Septic systems that are properly designed, installed, and maintained provide a safe and efficient way of disposing domestic sewage.  However, when sewage is discharged to antiquated or substandard sewage systems, such as cesspools, renovation of the wastewater by the soil may be incomplete.  Sewage contains pathogens (disease causing organisms) and if improperly disposed may result in health hazards and nuisance conditions.


Each year a week in September is chosen to highlight proper maintenance and care of septic systems. Not everyone has one, but if you do, maintenance is key to ensure a properly functioning septic system. 
This year, SepticSmart week is September 18 - 22, 2024

Did you know? Common household leaks can add hundreds of extra gallons of water every day, stressing your septic system. Overloading your septic system with water is a leading cause of failure. Save water and support your septic system’s health. For the long-term care of your system, have your septic tank inspected and pumped out by a CT licensed septic tank cleaner or installer as needed (on average every three to five years).

Click on the SepticSmart icon below for more information.



Septic systems on sites with design flows of 7,500* gallons per day (GPD) and less are permitted by the Local Director Health.  Additionally, plans for large septic systems serving buildings with design flows of 2,000 to 7,500 GPD must be approved by the CT Department of Public Health.  Septic systems, defined as subsurface sewage disposal systems, are regulated by Public Health Code (PHC) Section 19-13-B103 and the associated Technical Standards for Subsurface Sewage Disposal Systems (Technical Standards). Local Health Department contact information.  Septic systems on sites with design flows exceeding 7,500 GPD, alternative sewage disposal systems, and community sewage systems are permitted by the CT Department of Energy and Environmental Protection (CTDEEP).


*See Circular Letter 2017-17 that concerns new legislation (Public Act 17-146, Section 30) that affected subsurface sewage disposal system jurisdiction.

For general questions and to receive program notifications please e-mail
the Environmental Engineering Program at: dph.environeng@ct.gov


Additional Online Resources:


Statutes, Regulations and Technical Standards for Subsurface Sewage Disposal Systems 


*2024 Technical Standards for Subsurface Sewage Disposal Systems* (01/01/2024)  

Historical Technical Standards

Exception Applications 
All applications are for Local Health Department use only.  


We encourage electronic completion and submission utilizing the Electronic Form (eform) including scanned supporting documentation.  Please see Circular Letter 2011-70 Water Supply Well Separation Distance Exceptions and/or Circular Letter 2012-42 Central System Exceptions in the Environmental Engineering section under Environmental Health Section-Publications for additional requirements.  


  • Minimum Leaching System Spread (MLSS) 2023

  • Local Health Department Approved Agent Training (Phase I & II) will be held in the fall of 2024. Registration for current local health department staff will be open starting July 9, 2024 via TrainCT

Water Treatment Wastewater (WTW) 


Financial Assistance Programs

Inspections of Existing Septic Systems

Manufactured Select Fill 

Product Approvals

DPH Code Advisory Committee (CAC)


Historic CAC Agendas and Meeting Records:

  -8/24/2023 Meeting notes  

  -2023 Updated Summary of Proposed Revisions 11/18/2022

CAC Agenda 8/30/2022 (meeting link included) 

CAC Agenda 4/29/2021  

CAC meeting agenda 8/27/2020

-Summary of Proposed January 1, 2021 Technical Standards Revisions 

-Home Builders Letter 5/7/2020

-Circular Letter 2020-65 Technical Standards Revisions


Installer/Cleaner Exam Information