What Size Is a Dishwasher Drain?

Nathan McGinty

Dishwashers are helpful appliances, but after the dishes have been washed, the dirty water has to go somewhere. That's where dishwasher drain hoses come into play. The hose allows the used dishwater to be pumped back into the home sewage system, cleaning out the dishwasher for the next load.

Dishwasher Operation

Dishwasher hoses come in a different widths.

Water from the house enters the dishwasher through the water supply hose at the base of the dishwasher. A coupling on the end of the hose holds it tightly in place on the water inlet. The dishwasher mixes this water with soap and sprays it around the inside of the cabinet to clean the dishes. After the cleaning cycle is finished, the dirty dishwater is pumped out of the dishwasher through the drain hose.

Drain Hose Connection

The drain hose connects to the dishwasher at the drain pump located on the underside of the cabinet. The other end of the hose connects to the tailpiece located underneath the nearest sink. In homes with a garbage disposal, the drain hose can also attach to the side of the garbage disposal. At both ends, the drain hose is firmly held in place by a hose clamp and screw.

Drain Hose Routing

Because the dishwasher drain line usually is routed through a cabinet on the way to a the sink, holes need to be cut in cabinet walls as needed. Cuts can be made with a spade bit attached to a power drill. Once the holes are made, the edges should be sanded so they don't cut the drain line. The middle portion of the drain hose should be attached to the wall or the underside of the cabinet so it is higher than either end. This prevents water from flowing backward into the dishwasher.

Hose Sizing

Most dishwasher drain hoses are 1/2 inch in size. To allow for different types of connections at the end of the hose, dishwasher drain hoses are fitted with a special rubber boot. This allows them to connect to 1/2-inch, 3/4-inch and 1-inch connections. Usually the boots have markers indicating where to cut for the different widths. The hose is cut with a sharp utility knife and can be slipped into position.