Which system consists of a small bypass water line connected from the discharge side back to the intake side of the pump?

• A. Foam nozzle eductors
• B. Bypass-type balanced pressure proportioners
• C. Around-the-pump proportioners
• D. Variable-flow variable-rate direct injection systems

Answer: (C)

The main idea here is identifying foam-proportioning methods by how the concentrate is mixed with water and where the line that bypasses the pump is located. The system described uses a small bypass line that taps discharge water and returns it to the pump’s intake, with foam concentrate metered into that bypass. This setup allows the foam to be formed in a loop around the pump before it exits through the discharge—the hallmark of around-the-pump proportioners.

Foam nozzle eductors mix concentrate into water at the nozzle via a venturi effect, not with a bypass loop around the pump. Bypass-type balanced pressure proportioners do use a bypass to help regulate pressure and maintain ratio, but their arrangement isn’t the classic around-the-pump bypass around the pump intake. Variable-flow variable-rate direct injection systems meter concentrate directly into the water stream inline, without routing water back to the pump intake.