Ontario Septic System Guide
A plain-language guide to Ontario Building Code Part 8 sewage systems for rural and unserviced properties. Understand what you need before you build.
Professional Disclaimer
This is an AI-generated informational snapshot. It is NOT legal, engineering, architectural, or permitting advice. All data must be verified with the municipality and qualified licensed professionals. Do not make construction, purchasing, or investment decisions based solely on this report.
When Do You Need a Septic System?
If your property is not connected to a municipal sewer system, you will need a private sewage disposal system (commonly called a "septic system"). This applies to most rural properties and some properties in smaller municipalities.
The Ontario Building Code (OBC), Part 8 — Sewage Systems, governs the design, installation, and maintenance of all on-site sewage systems in Ontario. A sewage system permit is required before installation.
Common Septic System Types in Ontario
Class 4 — Conventional Septic
Septic tank + leaching bed. The most common system for residential properties. Requires adequate soil conditions and lot size.
Class 4 — Raised Bed
Similar to conventional but the leaching bed is raised above grade. Used when the water table is too high or soil conditions are poor.
Class 4 — Filter Bed
Uses imported sand as a filter medium. Required when native soil cannot adequately treat effluent.
Tertiary Treatment (Class 4 Advanced)
Mechanical treatment unit + dispersal. Used for challenging sites, small lots, or environmentally sensitive areas.
Holding Tank (Class 1)
A sealed tank that must be pumped regularly. Only permitted as a temporary or last-resort solution.
Privy / Outhouse (Class 2)
Permitted for seasonal properties only. Must meet setback requirements. Not suitable for year-round residential use.
Typical Setback Requirements
These are minimum setbacks from the OBC. Your municipality or conservation authority may require greater setbacks.
| Feature | From Septic Tank | From Leaching Bed |
|---|---|---|
| Well (drilled) | 15 m | 15 m |
| Well (dug/bored) | 15 m | 15 m |
| Property line | 1.5 m | 3 m |
| Building foundation | 1.5 m | 5 m |
| Lake or river | 15 m | 15 m |
| Ditch or swale | 5 m | 5 m |
| Swimming pool | 5 m | 5 m |
| Driveway | 1.5 m | 3 m |
Source: Ontario Building Code, Part 8. These are general minimums — always verify with your local building department.
Septic Permit Process
Site Evaluation
Hire a licensed septic designer to conduct a site evaluation. This includes soil testing (percolation test), measuring the water table, and assessing the available area for the system.
System Design
The septic designer creates a detailed system design based on the site evaluation, proposed building size (number of bedrooms), and daily flow calculations.
Permit Application
Submit the sewage system permit application to your local building department (or health unit, depending on the municipality). Include the site evaluation and system design.
Installation & Inspection
A licensed installer constructs the system. The building department inspects at key stages (tank placement, distribution piping, final cover).
Key Considerations for Builders
Soil Conditions Matter
Clay soils, high water tables, and bedrock can significantly increase system costs. Always get a site evaluation before committing to a project.
Lot Size Requirements
Minimum lot sizes for septic systems vary. A conventional system typically needs at least 0.4 hectares (1 acre). Smaller lots may require advanced systems.
Well Separation
The 15m minimum setback from wells is critical. On small lots, well and septic placement must be carefully coordinated during site planning.
Who Issues the Permit?
In most of Ontario, the local building department issues sewage system permits. Some areas delegate to the health unit. Always confirm with your municipality.
Professional Disclaimer
This is an AI-generated informational snapshot. It is NOT legal, engineering, architectural, or permitting advice. All data must be verified with the municipality and qualified licensed professionals. Do not make construction, purchasing, or investment decisions based solely on this report.
This guide is for general informational purposes only. Septic system requirements vary by municipality, soil conditions, and site characteristics. Always consult with a licensed septic designer and your local building department. Last updated: February 2026.