Which device is used to introduce foam concentrate into the water stream and is connected at the pump discharge?

• A. Portable foam maker
• B. Venturi injector
• C. Inline eductor
• D. External mixer

Answer: (C)

Foam concentrate is introduced into the water stream by devices that use the Venturi effect to entrain the concentrate as water flows. The inline eductor is placed directly in the pump discharge line, so all water passing from the pump goes through it. As the water speeds through the eductor, a low-pressure area is created that draws foam concentrate from its reservoir into the water stream via a suction line. The concentrate and water mix inside the eductor and exit as foam solution at the discharge.

This setup is ideal for connect-at-pump-discharge requirements because it’s simple, compact, requires no power, and uses the pump’s discharge pressure to reliably proportion foam concentrate into the water. It’s designed for straightforward installation and maintenance and works well for keeping a steady foam mix at the point of discharge.

Portable foam makers are stand-alone and not tied into the pump discharge, making them less suitable for sustained, high-volume use. A venturi injector can be similar in principle but is configured differently or used in other locations. An external mixer adds downstream piping and complexity, which isn’t as efficient as an inline eductor for this purpose.