In an inline balance-pressure proportioning system, where is the pressure regulating device that maintains constant pressure in the foam concentrate supply line placed?

• A. In the pump return line.
• B. In the water supply line.
• C. In the foam concentrate supply line.
• D. In the discharge line.

Answer: (A)

In inline balance-pressure proportioning, the pressure-regulating device is placed in the pump return line. This location lets the system keep the foam concentrate supply line at a constant pressure by routing excess pressure back to the pump suction, creating a stable differential across the proportioning point. With the regulator in the return path, changes in pump discharge pressure don’t directly drive the concentrate line pressure, so the foam concentrate is metered consistently regardless of flow. Placing the regulator elsewhere would not reliably stabilize the concentrate line pressure, which is essential for correct foam-to-water ratio.