Step 3 · Create a High Loop
To prevent dirty water from the sink from flowing back into the dishwasher, you must create a 'high loop'. Take the dishwasher drain hose and route it from the dishwasher appliance up towards the underside of the countertop. The highest point of the hose should be as high as possible within the sink cabinet, ideally touching the bottom of the counter. Secure the hose at this high point to the back of the cabinet wall or the counter itself using a pipe strap or a heavy-duty zip tie. From this peak, the hose should then slope continuously downward to the garbage disposal inlet.