Which parameter should not exceed 10 psi for the softener?

The correct parameter that should not exceed 10 psi for the softener is delta pressure. Delta pressure, which refers to the difference in pressure between the inlet and outlet of the softener, is critical for ensuring that the system operates efficiently. If delta pressure exceeds this limit, it can indicate blockages, fouling, or other issues within the system that could lead to inadequate flow rates or even damage to the softener.

Monitoring delta pressure is important because it is a direct indicator of the condition and performance of the softener. A too high delta pressure can stress the equipment and impair its ability to soften water properly. Keeping delta pressure at or below the specified threshold helps maintain the integrity and effectiveness of the softening process.

In contrast, other parameters like initial pressure, output pressure, and inlet pressure do not have the same critical threshold concern in the context of the performance of the softener. While it's necessary to monitor those pressures to ensure overall system functionality, delta pressure is the specific measurement tied to the operational condition of the softener that should be kept under 10 psi.