What size drain pipe does a kitchen sink need?

Kitchen sinks in Ontario require a minimum 1.5-inch drain pipe, though 2-inch drains are often preferred for better flow and reduced clogging, especially with garbage disposals or double sinks.

The drain tailpiece (the pipe directly under the sink) must be at least 1.5 inches in diameter according to the Ontario Building Code. However, many plumbers in Ottawa install 2-inch drains for kitchen sinks because they handle food particles and grease much better than the minimum size. The larger diameter reduces the chance of blockages and provides better long-term performance.

For Ottawa installations, the drain connects to your home's waste stack, which is typically 3 or 4 inches. The kitchen drain line should maintain proper slope (1/4 inch per foot minimum) to ensure good drainage flow. If you're renovating and have an older home with 1.25-inch kitchen drains, upgrading to 1.5 or 2 inches during the renovation is highly recommended.

Double sinks or sinks with garbage disposals particularly benefit from 2-inch drains. The additional capacity handles the increased waste volume and helps prevent the slow drainage that's common with undersized pipes. In Ottawa's older neighborhoods like the Glebe or Westboro, many homes still have smaller original drain lines that cause frequent kitchen sink backups.

Installation requires permits in Ottawa when modifying drain lines, and the work should be done by a licensed plumber to ensure proper venting and code compliance. City of Ottawa requirements may vary for specific installations, so confirm details with your licensed plumber.

For a free estimate on kitchen plumbing upgrades or drain line improvements, request a quote from Ottawa Pro Plumbing.