Which two conditions commonly cause back-flow in a distribution system?

Back-pressure and back siphonage are two conditions that commonly cause back-flow in a distribution system. Understanding these terms is crucial for maintaining safe and effective water treatment practices.

Back-pressure occurs when the pressure in a system downstream from a cross-connection is greater than the pressure in the water distribution system itself. This can lead to the reverse flow of contaminated water into the potable supply. Factors contributing to back-pressure can include pumps or elevated tanks that create higher pressure in certain parts of the system.

Back siphonage, on the other hand, happens when there is a negative pressure or vacuum created in the distribution system—usually due to a sudden drop in pressure, such as during a main break or fire hydrant usage. This can draw water from various sources, potentially including contaminated water, back into the clean water supply.

Together, both conditions pose significant risks for water quality, making it essential to design systems that prevent back-flow, such as using air gaps or backflow preventers.