Which practice is essential to prevent backflow in a distribution system?

• A. Maintaining continuous positive pressure
• B. Increasing flow velocity
• C. Reducing chlorine residual
• D. Isolating cross-connections completely

Answer: (A)

Maintaining continuous positive pressure in the distribution system is the key defense against backflow. When the system stays pressurized above the potential sources of contamination, water remains flowing outward from the distribution mains rather than being drawn back through cross-connections. This positive pressure helps prevent back-siphonage and reduces the chance that contaminants from a service line or customer side could enter the distribution system.

In practice, this means using proper pumping, storage, and pressure management to avoid pressure drops, especially at dead ends or during high demand. Backflow prevention devices at higher-risk connections are still important, but keeping the system under positive pressure is the foundational step that minimizes backflow risk.

The other options don’t offer the same protection. Increasing flow velocity doesn’t guarantee against reverse flow and can cause other issues; reducing chlorine residual undermines water quality; and isolating cross-connections is helpful but not always feasible as the sole measure. Maintaining continuous positive pressure is the most reliable safeguard.