Which method involves mixing foam concentrate with water in a batch before discharge to the foam system?

• A. Eduction
• B. Injection
• C. Batch-mixing
• D. Premixing

Answer: (C)

Batch-mixing is the method where a defined amount of foam concentrate is combined with water in a dedicated mixing vessel to create a ready-to-discharge foam solution, which is then sent into the foam system. The key idea is that the mixture is prepared in a batch with a precise ratio before it enters the system, ensuring consistent foam quality for that entire batch. This contrasts with eduction, which blends concentrate into the water stream on the fly via a venturi, and with injection, which uses a pump to inject concentrate into the water line during flow. Premixing involves mixing ahead of time as a stored or ready-to-discharge solution, but batch-mixing specifically emphasizes creating a batch in a mixer and then discharging it to the system.