Which statement about backflow preventers is incorrect?

Backflow preventers are crucial devices designed to protect water supplies from contamination resulting from reverse flow. The incorrect statement suggests that backflow preventers completely eliminate any risk of backflow. In reality, while they are very effective in preventing backflow, there are still conditions and situations under which backflow can occur, particularly if the device is not properly maintained, installed, or if the system experiences unusual pressure changes. Thus, while their purpose is to minimize the risk of contamination, it is not accurate to claim that they prevent any chance of backflow entirely.

In contrast, backflow preventers must be installed under pressure to function correctly, as they rely on water pressure to operate effectively. They are indeed used to protect water supplies from harmful contaminants and chemicals, making them critical in diverse applications, including agricultural settings where pesticides may be involved. Their design allows for safe pesticide application by ensuring that when chemicals are used, they do not accidentally flow back into the main water supply, thus safeguarding public health and the environment.