Sewage Treatment Systems

Many homeowners in the Thunder Bay District rely upon septic systems or “onsite sewage treatment systems”  to treat and disperse their sanitary wastewater. Approval for in-ground sewage treatment and dispersal is required in all parts of Ontario, including the unorganized lands.

The Thunder Bay District Health Unit provides permits for and inspects all new construction in the district to ensure that minimum requirements of the Ontario Building Code are met including regulations regarding the distance between septic systems and well water. The TBDHU also provides information and support to homeowners about proper maintenance of their septic system.

Under Part VIII of the Ontario Building Code, the TBDHU is responsible for issuing permits for the construction and use of sewage treatment systems (also referred to as septic systems) within the District of Thunder Bay. The TBDHU issues Certificates of Approval to construct/install Class 2 through 5 sewage systems for new homes, camps, businesses and for the addition or replacement of existing systems serving existing dwellings.


Part VIII of the Ontario Building Code specifies the minimum requirements for:

  • Five different classifications of sewage systems, and discharge limitations on sanitary sewage:
    • Class 1 Sewage System - Composting toilet, pit privy, vault privy.
    • Class 2 Sewage System - Leaching pit (used for the treatment and dispersal of grey water only).
    • Class 3 Sewage System - Cesspool (used for the treatment and dispersal of the contents of a Class 1 sewage system only).
    • Class 4 Sewage System - A conventional system includes a septic tank and leaching bed. An alternative system includes a septic tank and treatment unit and area bed (used for the treatment and dispersal of all wastewater).
    • Class 5 Sewage System - This system is a holding tank (contents must be pumped as often as is required). This system is permitted only by exemption under the Building Code. Contact the TBDHU for details.
  • Site evaluation regarding local soil conditions, sewage design flows and clearance requirements for various types of sewage systems.
  • Application of tanks used to collect, treat, hold or store sanitary sewage, as well as the construction and installation of sewage systems
  • The operation and maintenance requirements

Part VIII of the Ontario Building Code governs the design, construction, operation and maintenance of sewage treatment systems up to a capacity of 10,000 litres per day on one individual lot.

Sewage Systems that are greater than 10,000 litres per day (L/d), or if a single property contains several small systems (less than 10,000 L/d each) but the combined capacity of the systems exceeds 10,000 L/d, are subject to Ontario Ministry of Environment approval.


Land Development

Under the Planning Act, the TBDHU is requested by local Municipalities in organized territories and the Ontario Ministry of Municipal Affairs and Housing in the unorganized territories to comment on proposed severances, subdivisions, minor variances, zoning amendments and official plans from an in-ground sewage treatment and dispersal viewpoint.

Severances – an inspection performed to determine the suitability of a proposed piece of land from an in-ground sewage treatment and dispersal viewpoint (3 lots or fewer)

Subdivisions – same as above (4 lots or more)

Lot Inspection for Advice – an inspection performed on a lot already created to determine suitability for in-ground sewage treatment and dispersal

Real Estate Inspection – an inspection performed on an existing sewage system to facilitate a Real Estate transaction when the system was installed/constructed without TBDHU approval or a permit was not found in the information provided

Compliance Inspection – an inspection performed to facilitate mortgage requirements when present owner is unable to provide documentation indicating the system was installed/constructed with TBDHU approval

Complaint/Enforcement Inspection – All complaints or enquiries regarding sewage treatment systems are investigated. If and when a contravention of the Ontario Building Code has been identified, the party in question is given every opportunity and technical assistance to achieve compliance. Enforcement of the Code through legal means is usually employed when all other avenues have failed.

File Searches – This procedure can be requested by the public to search TBDHU files to determine if the property in question is serviced with a TBDHU-approved sewage system. If a permit is found, a copy is generated and is made available. The TBDHU can only access files from 1980 to the present.

Performance Level Review – This service is performed to determine if a proposed addition to a dwelling will reduce the performance level of the sewage system. For example, if the proposed addition is expected to increase the daily wastewater flow beyond the capacity of the sewage system, the system may have to be enlarged.


Septic System Use Do’s and Don’ts


  • Familiarize yourself with the location of your septic system and, if it has one, the electrical control panel
  • Keep an "as-built" system diagram in a safe place for reference; provide future owners with a copy
  • Divert surface water away from your leaching bed
  • Pump out your septic tank on a regular basis (every 3-5 years)
  • Repair leaky plumbing fixtures to conserve water and reduce the amount of wastewater that must be treated.
  • Replace old toilets with low-flush models
  • Keep lint out of your system by cleaning the lint filters on your washing machine
  • Flush toilets with solid waste only. "If it's yellow let it mellow. If it's brown flush it down."
  • Run full loads in both your washing machine and dishwasher
  • Spread out laundry loads as much as possible
  • Have showers instead of baths whenever possible
  • Keep the tank access lid secure to the riser at all times
  • Keep accurate records of system maintenance and service calls
  • Maintain your system as required by cleaning your effluent filter annually OR as often as required



  • Flush hazardous chemicals
  • Flush cigarette butts or sanitary products
  • Use a garbage disposal/garburator
  • Plant trees or shrubs too close to the septic system or leaching bed
  • Use special additives that claim to enhance the performance of your tank or system
  • Use excessive amounts of water
  • Leave interior taps running when attempting to prevent water lines from freezing
  • Dig without knowing the location of your sewage system
  • Drive over your septic tank or any buried components in your sewage system
  • Dump RV waste into your septic tank
  • Enter a septic tank
  • Connect rain gutters, storm drains or allow surface water to drain into a sewage system
  • Flush substances that cause maintenance problems and/or increase the need for septic tank pumping
  • Remove and throw away the effluent filter to avoid cleaning it


For Further Information

Call a Public Health Inspector: (807) 625-5900

toll-free 1-888-294-6630

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