Which condition can lead to the occurrence of back siphonage?

Back siphonage occurs when there is a reversal of flow in the water supply system, often facilitated by a drop in water pressure. A break in the city main is a critical factor that can lead to this condition. When a city water main breaks, it can create a significant drop in pressure. This drop allows contaminated water from nearby sources, such as irrigation systems or sewage lines, to be drawn back into the clean water supply due to the negative pressure gradient created by the break.

Other factors like high elevation storage tanks may influence pressure dynamics but are less likely to directly cause back siphonage compared to a break in the city main. Similarly, reduction in water usage or installation of low flow fixtures generally lead to more stable pressure environments, reducing the risk of back siphonage rather than increasing it. Understanding how pressure changes can impact water flow is essential for maintaining safe and effective irrigation practices.