How to Make Dishwasher Drain Hose Connections

As part of the overall installation of a dishwasher, hooking up the drain is usually pretty easy, but it’s important to understand the different options when doing so, with or without a garbage disposal.

If you are removing a dishwasher and replacing it with a new one, it is usually easiest to simply copy the same drain hookups that were used on the old dishwasher. But if you are adding a dishwasher for the first time, you may need to install a special drain fitting known as a Y-branch tailpiece to give the dirty water a place to flow into your drain system.

The different drain variations you may encounter include:

• Drain line connected through an air gap to the garbage disposal
• Drain line connected through an air gap directly to the drain
• Drain line configured in a “high loop” to the garbage disposal
• Drain line configured in a “high loop” directly to the drain

An air gap fitting is a safety device mounted on your sink or countertop, through which the dishwasher hose passes on its way to the drain. It provides a pressure break in the drain line that prevents the possibility of dirty drain water being back-siphoned into a dishwasher filled with clean dishes. Not all dishwashers use this device; another alternative is what is known as the “high loop” installation, in which the drain line loops up under the sink base cabinet to a point above the dishwasher’s water level to prevent any backflow. 

The tools and materials you need to connect a dishwasher drain will vary, depending on the configuration and whether or not there is an air gap. In all cases, be sure to turn the water off under the sink and unplug your garbage disposal (if you have one) before beginning.