How to Connect a Drain Hose from a Dishwasher to the Drain Pipe of a Double Sink

Place a bucket beneath the P-trap. Note the parts of the undersink drain assembly. In most cases, the P-trap connects to a T-fitting, which connects to a horizontal pipe and a vertical pipe. You will replace the vertical pipe with the branch tailpiece. Wrap a rag around the nut that connects the vertical pipe to the T-fitting.

Twist the nut counterclockwise by hand. If the nut sticks, leave the rag in place and grip the nut with pliers. Twist the nut until it is loose and freely slides away from the T-fitting. Allow water to drain into the bucket. Wrap the rag around the nut that connects the vertical pipe to the sink basin. Loosen the nut by hand or with pliers.

Slip the vertical pipe out of the T-fitting and remove the pipe from the sink basin. Remove the nut and washer from the pipe. Slide the nut that you removed from the pipe onto the smooth end of the branch tailpiece. Slide the washer that you removed onto the smooth end of the branch tailpiece.

Insert the smooth end of the tailpiece into the T-fitting and the align the opposite end, which has a factory-installed nut, with the sink basin's strainer. Thread the top end of the tailpiece to the sink strainer and the bottom end of the tailpiece to the T-fitting. Tighten roughly 1/4 turn past hand-tight.

Remove the air gap assembly's cover from its Y-shaped body. Stick the cylindrical portion of the air gap through the underside of the sink rim. Attach the cover to the cylindrical portion of the air gap to secure the air gap assembly to the sink rim. Slip one end of the air gap assembly's hose over one of the air gap's barbed outlets, and the other end of the hose over the branch tailpiece's small tube.

Fasten the air gap hose to both the air gap outlet and the branch tailpiece with screw clamps or spring clamps, usually included with the air gap assembly. If your assembly includes screw clamps, use a screwdriver to tighten the clamps.

Pull the dishwasher away from the wall. Slide the end of the dishwasher drain hose over the dishwasher's drain outlet tube. Secure the hose to the outlet tube with screw or spring clamps, usually included with the drain assembly. Route the hose through the side of the cabinet. Slide the open end of the hose over the remaining air gap tube. Secure the hose to the air gap with screw or spring clamps.