Which of the following increases the risk of backflow in a water system?

Low water pressure in a water system significantly increases the risk of backflow. Backflow occurs when the normal flow of water is reversed, allowing potentially contaminated water from a source back into the clean water supply. When water pressure is low, it can create conditions where negative pressure or a vacuum is formed in the system. This can happen during periods of high water demand or when there is a sudden change in system pressure, such as a main break or fire hydrant use.

In these scenarios, if there's a connection from a non-potable water source, such as irrigation systems or chemical storage, the lower pressure may not be sufficient to keep the contaminated water from flowing back into the potable water supply. Thus, maintaining adequate water pressure is crucial for preventing backflow and ensuring the safety of the drinking water supply.