Close up of a sink drain

Sink Drain

Originally contributed by • last updated 2/22/2021

Renovating your kitchen or bathroom can be a very rewarding experience but it can also be challenging if you’re not prepared for the worst. If you end up needing to repair or replace the sink drain in your kitchen or bathroom, there are a few things you should know before you get started. Like, what’s a sink stopper and do you need a P trap?


The term sink drain commonly refers to the plumbing network that connects the bottom of the sink basin to the main sewer drain. Typically, the drain itself is made of a network of parts consists of connectors, washers, gaskets, and pipes, as well as, the sink strainer and the drain trap (usually referred to as a P trap or an S trap). Together, the drain parts are designed to strain and block solids, while allowing liquids to exit through to the main waste water pipe. A kitchen sink drain may have additional plumbing attachments for a pull down kitchen faucet, dishwasher, and/or garbage disposal. Likewise, a bathroom sink drain may contain additional pieces for a sink stopper.

What Size Pipe Is Needed For A Sink Drain?

Selecting the right size drain pipe to connect to your bathroom or kitchen sink is not only important, it’s actually required by building codes in certain locations. Luckily, for most homeowners, there are only a couple of options to deal with so it’s not too difficult to get it right:

  • In most situations, sink drains in the bathroom are easier to work with than ones in the kitchen because there are often less parts involved in the drain assembly. With most bathroom sinks, the drain pipe only needs to be 1 ¼ inches in diameter, while some others use a 1 ½ inch pipe.
  • Kitchen sink drains are a bit more difficult to work with than ones in the bathroom because there are typically more parts required for pull-down faucets and garbage disposal hook-ups. However, the actual drain pipe that leads away from the drain assembly is still most commonly 1 ½ inches in diameter, with some being as large as 2 inches or more.
  • Pro-Tip: If you’re considering using a larger sink drain pipe for better efficiency, think again. Larger drain pipes may not actually improve performance in most residential situations and typically cost more money.