Which term describes the contamination of the water supply because of a negative pressure condition?

The term that describes the contamination of the water supply due to a negative pressure condition is back-siphonage. This phenomenon occurs when there is a drop in water pressure in the supply line, creating a vacuum or negative pressure that can draw water (and potential contaminants) from an open source back into the clean water supply.

Back-siphonage typically happens when there is a sudden demand for water, such as when a fire hydrant is opened, or when there is a break in the water main. In these situations, if there are connections where non-potable water or contaminants can enter the system, the negative pressure can pull these substances into the drinking water supply.

Understanding this concept is crucial for preventing contamination in plumbing systems. This highlights the importance of maintaining proper pressure in the water supply and adhering to plumbing codes that regulate cross connections and other potential risks.