A dishwasher discharge pipe must rise to which position before being connected?

A dishwasher discharge pipe must rise to the underside of the counter before being connected to ensure proper drainage and prevent backflow. This requirement is part of maintaining a high loop or air gap system, which helps to protect the potable water supply from contamination. By elevating the discharge pipe to the underside of the counter, it creates a natural barrier that prevents wastewater from siphoning back into the clean water supply, thus upholding health and safety standards in plumbing.

The alternatives would not fulfill the necessary function of preventing potential backflow. If the discharge pipe were connected at the top of the sink, it may still allow backflow if the plumbing system experiences negative pressure. Connecting it to the floor level would not offer the required height to prevent contaminants from re-entering the potable water system. Lastly, connecting the pipe to the ceiling height would be impractical and does not serve the intended purpose of safeguarding the water supply from contamination.