What can cause backflow in a water system?

Backflow in a water system occurs when water flows in the reverse direction, which can contaminate the potable water supply. One of the primary causes of backflow is negative or below atmospheric pressure in the system. This condition can create a vacuum effect that draws water from the distribution system or even from unprotected sources, leading to the potential for contaminants to enter the drinking water supply.

For instance, if a large amount of water is drawn from a fire hydrant or during maintenance procedures on a nearby pipeline, it may create negative pressure in the system. This negative pressure can cause water to flow back into the system from lower pressure areas or even from nearby contaminated sources. Understanding this mechanism is critical for water operators to prevent backflow incidents and ensure safe drinking water.

The other options do not directly cause backflow in a similar manner. Excessive lighting in treatment facilities does not influence flow dynamics. Lack of water filtration does not create conditions for backflow, though it can lead to water quality issues. High water table levels might affect groundwater and surface water interactions but are not a direct cause of backflow.