Full-flow testing of the proportioning system and discharge device is required to properly evaluate the proportioning system. Which option represents this requirement?

• A. Visual inspection
• B. Functional test with one actuator
• C. Full-flow testing
• D. Pressure test only

Answer: (C)

In foam-water systems, the proportioning performance must be verified under the actual flow conditions the system will experience. Full-flow testing is necessary because the way the concentrate is mixed with water can change as flow increases; a device that meters correctly at a small or no-flow condition might not maintain the required foam-concentration ratio at design discharge rates. By running the entire proportioning system and discharge device at design flow, you can confirm that the concentrate is being proportioned accurately across the full range of operation and that every discharge point receives the correct foam solution.

During full-flow testing, you simulate the system’s normal demand, verify that the proportioning device delivers the intended concentrate-to-water ratio (for example, the specified percentage of foam concentrate in the solution), and ensure the discharge devices operate properly with the correct mixture. You also confirm that the overall hydraulic performance remains within limits, valves and interlocks function, and there are no unintended leaks or backflow affecting the mix.

Visual inspection or a test with only a single actuator does not reveal whether the ratio is maintained under actual operating flow, and a pressure test alone checks piping integrity without confirming proportioning accuracy.