2024 Ontario Building Code: Manholes, Cleanouts, and Drainage Slope Guide for London Projects
Sarah's Expert Insight
OBC Compliance Specialist
"In London and the surrounding Oakville areas, soil conditions can vary significantly, making the 1 in 50 slope requirement for smaller drainage pipes non-negotiable to prevent settling-related backups. At empcontracting.ca Inc., we emphasize precision in manhole channeling and cleanout accessibility to ensure our clients avoid the high costs of future infrastructure failures."
Understanding the complexities of the 2024 Ontario Building Code (OBC) is essential for any successful residential or commercial build. As empcontracting.ca Inc. your construction contractor in London, Ontario, we ensure every aspect of your drainage system—from manhole dimensions to pipe slopes—meets or exceeds provincial standards.
OBC 7.4.7.3: Manhole Design and Location Requirements
Manholes serve as critical access points for the maintenance of storm building sewers and exterior drainage pipes. According to the OBC, manholes are mandatory for pipes NPS 8 or larger at any change in grade, size, or alignment.
Key Manhole Specifications
- Dimensions: A minimum horizontal dimension of 1.2 m is required, with a specific taper allowed at the top 1.5 m.
- Safety: Rigid, corrosion-resistant ladders must be installed if the depth exceeds 1 m.
- Indoor Requirements: If located within a building, manholes must feature airtight covers and exterior venting to prevent hazardous gas accumulation.
OBC 7.4.7.4: Location and Accessibility of Cleanouts
Cleanouts are the first line of defense against drainage blockages. The code dictates that cleanouts must be readily accessible and positioned to allow for efficient drain cleaning without creating safety hazards in floor assemblies.
Technical Cleanout Standards
- Directional Changes: Piping changes between cleanouts must utilize 45-degree bends to facilitate smooth cleaning tool passage.
- Specialized Facilities: In healthcare or laboratory settings where contamination risk is high, cleanouts must be elevated at least 150 mm above the fixture's flood level rim.
- Urinals: Vertical drainage for wall-hung urinals requires a dedicated cleanout extending above the flood level rim.
OBC 7.4.8.1: Minimum Slope for Drainage Piping
Proper gravity flow is vital to a functional plumbing system. The standard requirement for drainage pipes NPS 3 or less is a downward slope of at least 1 in 50 (2%).
Exceptions to the Slope Rule
While the 1 in 50 slope is the benchmark, the code allows for a lesser slope if it can be engineered to produce a gravity flow of no less than 0.6 meters per second, ensuring solids remain in suspension and preventing system clogs.
Disclaimer: This content is generated from the Ontario Building Code for educational purposes. Always consult with a licensed professional engineer or your local building department before starting any construction project in London, Ontario.