Sanitary Sewer Downspout Disconnection Program

picture of a downspout

The objective of this multi-phase program is to reduce the risk of basement flooding and environmental concerns caused by the direct connection of downspouts to the sanitary sewer system. These connections create an increased flow of rainwater into the sanitary sewer system during heavy or long-duration rain events, which can in turn cause:

  • Overflow of sanitary sewer system
  • Sanitary sewer backups
  • Basement flooding

This program also enforces the existing City of Markham Sewer By-Law # 2014-71 [Clauses 3.1D & 19.11] and the Region of York’s Sewage and Land Drainage By-Law # S-0064-2005-009, which prohibit the discharge of roof drainage water into the sanitary sewer system.

Currently, this program is expected to be completed in five phases. Each area of focus within the City has been placed in a particular phase of the program based on available historical information including flow data and operational records of sewer backup/basement flooding. Please note that the number of phases, identified program areas, priority of the areas and the overall program implementation time are subject to change. This is based on the annual risk evaluation of different areas within the City taking into consideration the most up-to-date flow monitoring results, flooding records, and the improvement to the system due to other initiatives/programs.