When using an in-line eductor, the back pressure must not exceed what percentage of the inlet pressure?

When using an in-line eductor, it is critical to maintain back pressure at or below a certain percentage of the inlet pressure to ensure proper operation of the device. The correct percentage is 70%. If the back pressure exceeds this threshold, the eductor may not create the necessary vacuum to draw water or foam concentrate into the stream effectively. This is because excessive back pressure can disrupt the suction created by the eductor, leading to a failure in the mixing process.

Keeping the back pressure at or below 70% allows the eductor to function efficiently, ensuring an adequate flow of the liquid being used. This principle is essential for maintaining the effectiveness of fire suppression systems that utilize in-line eductors, as the proper mixing of water with foam concentrate or other agents is vital for achieving the desired extinguishing effect.