Which device type is commonly used as a foam concentrate proportioner?

• A. Inline eductor or external proportioning device.
• B. Check valve.
• C. Gate valve.
• D. Relief valve.

Answer: (A)

Foam concentrate needs to be mixed with water at a specific ratio before it reaches the system outlets. The device used to achieve that proportioning is typically an inline eductor in the water line or an external proportioning device. It works on the Venturi principle, drawing foam concentrate into the flowing water and mixing it to the intended concentration, so the foam solution is produced consistently across different flow rates. This simple, reliable method is why it’s the common choice for foam proportioning.

Backflow prevention (check valve), flow isolation (gate valve), and pressure relief (relief valve) aren’t used to mix foam concentrate; they serve to protect system integrity rather than proportion foam.